zig/lib/std/debug.zig
Alex Rønne Petersen 9ab7eec23e represent Mac Catalyst as aarch64-maccatalyst-none rather than aarch64-ios-macabi
Apple's own headers and tbd files prefer to think of Mac Catalyst as a distinct
OS target. Earlier, when DriverKit support was added to LLVM, it was represented
a distinct OS. So why Apple decided to only represent Mac Catalyst as an ABI in
the target triple is beyond me. But this isn't the first time they've ignored
established target triple norms (see: armv7k and aarch64_32) and it probably
won't be the last.

While doing this, I also audited all Darwin OS prongs throughout the codebase
and made sure they cover all the tags.
2025-11-14 11:33:35 +01:00

1776 lines
72 KiB
Zig

const std = @import("std.zig");
const Io = std.Io;
const Writer = std.Io.Writer;
const tty = std.Io.tty;
const math = std.math;
const mem = std.mem;
const posix = std.posix;
const fs = std.fs;
const testing = std.testing;
const Allocator = mem.Allocator;
const File = std.fs.File;
const windows = std.os.windows;
const builtin = @import("builtin");
const native_arch = builtin.cpu.arch;
const native_os = builtin.os.tag;
const StackTrace = std.builtin.StackTrace;
const root = @import("root");
pub const Dwarf = @import("debug/Dwarf.zig");
pub const Pdb = @import("debug/Pdb.zig");
pub const ElfFile = @import("debug/ElfFile.zig");
pub const Info = @import("debug/Info.zig");
pub const Coverage = @import("debug/Coverage.zig");
pub const cpu_context = @import("debug/cpu_context.zig");
/// This type abstracts the target-specific implementation of accessing this process' own debug
/// information behind a generic interface which supports looking up source locations associated
/// with addresses, as well as unwinding the stack where a safe mechanism to do so exists.
///
/// The Zig Standard Library provides default implementations of `SelfInfo` for common targets, but
/// the implementation can be overriden by exposing `root.debug.SelfInfo`. Setting `SelfInfo` to
/// `void` indicates that the `SelfInfo` API is not supported.
///
/// This type must expose the following declarations:
///
/// ```
/// pub const init: SelfInfo;
/// pub fn deinit(si: *SelfInfo, gpa: Allocator) void;
///
/// /// Returns the symbol and source location of the instruction at `address`.
/// pub fn getSymbol(si: *SelfInfo, gpa: Allocator, address: usize) SelfInfoError!Symbol;
/// /// Returns a name for the "module" (e.g. shared library or executable image) containing `address`.
/// pub fn getModuleName(si: *SelfInfo, gpa: Allocator, address: usize) SelfInfoError![]const u8;
///
/// /// Whether a reliable stack unwinding strategy, such as DWARF unwinding, is available.
/// pub const can_unwind: bool;
/// /// Only required if `can_unwind == true`.
/// pub const UnwindContext = struct {
/// /// An address representing the instruction pointer in the last frame.
/// pc: usize,
///
/// pub fn init(ctx: *cpu_context.Native, gpa: Allocator) Allocator.Error!UnwindContext;
/// pub fn deinit(ctx: *UnwindContext, gpa: Allocator) void;
/// /// Returns the frame pointer associated with the last unwound stack frame.
/// /// If the frame pointer is unknown, 0 may be returned instead.
/// pub fn getFp(uc: *UnwindContext) usize;
/// };
/// /// Only required if `can_unwind == true`. Unwinds a single stack frame, returning the frame's
/// /// return address, or 0 if the end of the stack has been reached.
/// pub fn unwindFrame(si: *SelfInfo, gpa: Allocator, context: *UnwindContext) SelfInfoError!usize;
/// ```
pub const SelfInfo = if (@hasDecl(root, "debug") and @hasDecl(root.debug, "SelfInfo"))
root.debug.SelfInfo
else switch (std.Target.ObjectFormat.default(native_os, native_arch)) {
.coff => if (native_os == .windows) @import("debug/SelfInfo/Windows.zig") else void,
.elf => switch (native_os) {
.freestanding, .other => void,
else => @import("debug/SelfInfo/Elf.zig"),
},
.macho => @import("debug/SelfInfo/MachO.zig"),
.plan9, .spirv, .wasm => void,
.c, .hex, .raw => unreachable,
};
pub const SelfInfoError = error{
/// The required debug info is invalid or corrupted.
InvalidDebugInfo,
/// The required debug info could not be found.
MissingDebugInfo,
/// The required debug info was found, and may be valid, but is not supported by this implementation.
UnsupportedDebugInfo,
/// The required debug info could not be read from disk due to some IO error.
ReadFailed,
OutOfMemory,
Canceled,
Unexpected,
};
pub const simple_panic = @import("debug/simple_panic.zig");
pub const no_panic = @import("debug/no_panic.zig");
/// A fully-featured panic handler namespace which lowers all panics to calls to `panicFn`.
/// Safety panics will use formatted printing to provide a meaningful error message.
/// The signature of `panicFn` should match that of `defaultPanic`.
pub fn FullPanic(comptime panicFn: fn ([]const u8, ?usize) noreturn) type {
return struct {
pub const call = panicFn;
pub fn sentinelMismatch(expected: anytype, found: @TypeOf(expected)) noreturn {
@branchHint(.cold);
std.debug.panicExtra(@returnAddress(), "sentinel mismatch: expected {any}, found {any}", .{
expected, found,
});
}
pub fn unwrapError(err: anyerror) noreturn {
@branchHint(.cold);
std.debug.panicExtra(@returnAddress(), "attempt to unwrap error: {s}", .{@errorName(err)});
}
pub fn outOfBounds(index: usize, len: usize) noreturn {
@branchHint(.cold);
std.debug.panicExtra(@returnAddress(), "index out of bounds: index {d}, len {d}", .{ index, len });
}
pub fn startGreaterThanEnd(start: usize, end: usize) noreturn {
@branchHint(.cold);
std.debug.panicExtra(@returnAddress(), "start index {d} is larger than end index {d}", .{ start, end });
}
pub fn inactiveUnionField(active: anytype, accessed: @TypeOf(active)) noreturn {
@branchHint(.cold);
std.debug.panicExtra(@returnAddress(), "access of union field '{s}' while field '{s}' is active", .{
@tagName(accessed), @tagName(active),
});
}
pub fn sliceCastLenRemainder(src_len: usize) noreturn {
@branchHint(.cold);
std.debug.panicExtra(@returnAddress(), "slice length '{d}' does not divide exactly into destination elements", .{src_len});
}
pub fn reachedUnreachable() noreturn {
@branchHint(.cold);
call("reached unreachable code", @returnAddress());
}
pub fn unwrapNull() noreturn {
@branchHint(.cold);
call("attempt to use null value", @returnAddress());
}
pub fn castToNull() noreturn {
@branchHint(.cold);
call("cast causes pointer to be null", @returnAddress());
}
pub fn incorrectAlignment() noreturn {
@branchHint(.cold);
call("incorrect alignment", @returnAddress());
}
pub fn invalidErrorCode() noreturn {
@branchHint(.cold);
call("invalid error code", @returnAddress());
}
pub fn integerOutOfBounds() noreturn {
@branchHint(.cold);
call("integer does not fit in destination type", @returnAddress());
}
pub fn integerOverflow() noreturn {
@branchHint(.cold);
call("integer overflow", @returnAddress());
}
pub fn shlOverflow() noreturn {
@branchHint(.cold);
call("left shift overflowed bits", @returnAddress());
}
pub fn shrOverflow() noreturn {
@branchHint(.cold);
call("right shift overflowed bits", @returnAddress());
}
pub fn divideByZero() noreturn {
@branchHint(.cold);
call("division by zero", @returnAddress());
}
pub fn exactDivisionRemainder() noreturn {
@branchHint(.cold);
call("exact division produced remainder", @returnAddress());
}
pub fn integerPartOutOfBounds() noreturn {
@branchHint(.cold);
call("integer part of floating point value out of bounds", @returnAddress());
}
pub fn corruptSwitch() noreturn {
@branchHint(.cold);
call("switch on corrupt value", @returnAddress());
}
pub fn shiftRhsTooBig() noreturn {
@branchHint(.cold);
call("shift amount is greater than the type size", @returnAddress());
}
pub fn invalidEnumValue() noreturn {
@branchHint(.cold);
call("invalid enum value", @returnAddress());
}
pub fn forLenMismatch() noreturn {
@branchHint(.cold);
call("for loop over objects with non-equal lengths", @returnAddress());
}
pub fn copyLenMismatch() noreturn {
@branchHint(.cold);
call("source and destination arguments have non-equal lengths", @returnAddress());
}
pub fn memcpyAlias() noreturn {
@branchHint(.cold);
call("@memcpy arguments alias", @returnAddress());
}
pub fn noreturnReturned() noreturn {
@branchHint(.cold);
call("'noreturn' function returned", @returnAddress());
}
};
}
/// Unresolved source locations can be represented with a single `usize` that
/// corresponds to a virtual memory address of the program counter. Combined
/// with debug information, those values can be converted into a resolved
/// source location, including file, line, and column.
pub const SourceLocation = struct {
line: u64,
column: u64,
file_name: []const u8,
pub const invalid: SourceLocation = .{
.line = 0,
.column = 0,
.file_name = &.{},
};
};
pub const Symbol = struct {
name: ?[]const u8,
compile_unit_name: ?[]const u8,
source_location: ?SourceLocation,
pub const unknown: Symbol = .{
.name = null,
.compile_unit_name = null,
.source_location = null,
};
};
/// Deprecated because it returns the optimization mode of the standard
/// library, when the caller probably wants to use the optimization mode of
/// their own module.
pub const runtime_safety = switch (builtin.mode) {
.Debug, .ReleaseSafe => true,
.ReleaseFast, .ReleaseSmall => false,
};
/// Whether we can unwind the stack on this target, allowing capturing and/or printing the current
/// stack trace. It is still legal to call `captureCurrentStackTrace`, `writeCurrentStackTrace`, and
/// `dumpCurrentStackTrace` if this is `false`; it will just print an error / capture an empty
/// trace due to missing functionality. This value is just intended as a heuristic to avoid
/// pointless work e.g. capturing always-empty stack traces.
pub const sys_can_stack_trace = switch (builtin.cpu.arch) {
// `@returnAddress()` in LLVM 10 gives
// "Non-Emscripten WebAssembly hasn't implemented __builtin_return_address".
// On Emscripten, Zig only supports `@returnAddress()` in debug builds
// because Emscripten's implementation is very slow.
.wasm32,
.wasm64,
=> native_os == .emscripten and builtin.mode == .Debug,
// `@returnAddress()` is unsupported in LLVM 21.
.bpfel,
.bpfeb,
=> false,
else => true,
};
/// Allows the caller to freely write to stderr until `unlockStdErr` is called.
///
/// During the lock, any `std.Progress` information is cleared from the terminal.
pub fn lockStdErr() void {
std.Progress.lockStdErr();
}
pub fn unlockStdErr() void {
std.Progress.unlockStdErr();
}
/// Allows the caller to freely write to stderr until `unlockStderrWriter` is called.
///
/// During the lock, any `std.Progress` information is cleared from the terminal.
///
/// The lock is recursive, so it is valid for the same thread to call `lockStderrWriter` multiple
/// times. The primary motivation is that this allows the panic handler to safely dump the stack
/// trace and panic message even if the mutex was held at the panic site.
///
/// The returned `Writer` does not need to be manually flushed: flushing is performed automatically
/// when the matching `unlockStderrWriter` call occurs.
pub fn lockStderrWriter(buffer: []u8) struct { *Writer, tty.Config } {
const global = struct {
var conf: ?tty.Config = null;
};
const w = std.Progress.lockStderrWriter(buffer);
// The stderr lock also locks access to `global.conf`.
if (global.conf == null) {
global.conf = .detect(.stderr());
}
return .{ w, global.conf.? };
}
pub fn unlockStderrWriter() void {
std.Progress.unlockStderrWriter();
}
/// Print to stderr, silently returning on failure. Intended for use in "printf
/// debugging". Use `std.log` functions for proper logging.
///
/// Uses a 64-byte buffer for formatted printing which is flushed before this
/// function returns.
pub fn print(comptime fmt: []const u8, args: anytype) void {
var buffer: [64]u8 = undefined;
const bw, _ = lockStderrWriter(&buffer);
defer unlockStderrWriter();
nosuspend bw.print(fmt, args) catch return;
}
/// Marked `inline` to propagate a comptime-known error to callers.
pub inline fn getSelfDebugInfo() !*SelfInfo {
if (SelfInfo == void) return error.UnsupportedTarget;
const S = struct {
var self_info: SelfInfo = .init;
};
return &S.self_info;
}
/// Tries to print a hexadecimal view of the bytes, unbuffered, and ignores any error returned.
/// Obtains the stderr mutex while dumping.
pub fn dumpHex(bytes: []const u8) void {
const bw, const ttyconf = lockStderrWriter(&.{});
defer unlockStderrWriter();
dumpHexFallible(bw, ttyconf, bytes) catch {};
}
/// Prints a hexadecimal view of the bytes, returning any error that occurs.
pub fn dumpHexFallible(bw: *Writer, ttyconf: tty.Config, bytes: []const u8) !void {
var chunks = mem.window(u8, bytes, 16, 16);
while (chunks.next()) |window| {
// 1. Print the address.
const address = (@intFromPtr(bytes.ptr) + 0x10 * (std.math.divCeil(usize, chunks.index orelse bytes.len, 16) catch unreachable)) - 0x10;
try ttyconf.setColor(bw, .dim);
// We print the address in lowercase and the bytes in uppercase hexadecimal to distinguish them more.
// Also, make sure all lines are aligned by padding the address.
try bw.print("{x:0>[1]} ", .{ address, @sizeOf(usize) * 2 });
try ttyconf.setColor(bw, .reset);
// 2. Print the bytes.
for (window, 0..) |byte, index| {
try bw.print("{X:0>2} ", .{byte});
if (index == 7) try bw.writeByte(' ');
}
try bw.writeByte(' ');
if (window.len < 16) {
var missing_columns = (16 - window.len) * 3;
if (window.len < 8) missing_columns += 1;
try bw.splatByteAll(' ', missing_columns);
}
// 3. Print the characters.
for (window) |byte| {
if (std.ascii.isPrint(byte)) {
try bw.writeByte(byte);
} else {
// Related: https://github.com/ziglang/zig/issues/7600
if (ttyconf == .windows_api) {
try bw.writeByte('.');
continue;
}
// Let's print some common control codes as graphical Unicode symbols.
// We don't want to do this for all control codes because most control codes apart from
// the ones that Zig has escape sequences for are likely not very useful to print as symbols.
switch (byte) {
'\n' => try bw.writeAll(""),
'\r' => try bw.writeAll(""),
'\t' => try bw.writeAll(""),
else => try bw.writeByte('.'),
}
}
}
try bw.writeByte('\n');
}
}
test dumpHexFallible {
const bytes: []const u8 = &.{ 0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88, 0x99, 0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff, 0x01, 0x12, 0x13 };
var aw: Writer.Allocating = .init(std.testing.allocator);
defer aw.deinit();
try dumpHexFallible(&aw.writer, .no_color, bytes);
const expected = try std.fmt.allocPrint(std.testing.allocator,
\\{x:0>[2]} 00 11 22 33 44 55 66 77 88 99 AA BB CC DD EE FF .."3DUfw........
\\{x:0>[2]} 01 12 13 ...
\\
, .{
@intFromPtr(bytes.ptr),
@intFromPtr(bytes.ptr) + 16,
@sizeOf(usize) * 2,
});
defer std.testing.allocator.free(expected);
try std.testing.expectEqualStrings(expected, aw.written());
}
/// The pointer through which a `cpu_context.Native` is received from callers of stack tracing logic.
pub const CpuContextPtr = if (cpu_context.Native == noreturn) noreturn else *const cpu_context.Native;
/// Invokes detectable illegal behavior when `ok` is `false`.
///
/// In Debug and ReleaseSafe modes, calls to this function are always
/// generated, and the `unreachable` statement triggers a panic.
///
/// In ReleaseFast and ReleaseSmall modes, calls to this function are optimized
/// away, and in fact the optimizer is able to use the assertion in its
/// heuristics.
///
/// Inside a test block, it is best to use the `std.testing` module rather than
/// this function, because this function may not detect a test failure in
/// ReleaseFast and ReleaseSmall mode. Outside of a test block, this assert
/// function is the correct function to use.
pub fn assert(ok: bool) void {
if (!ok) unreachable; // assertion failure
}
/// Invokes detectable illegal behavior when the provided slice is not mapped
/// or lacks read permissions.
pub fn assertReadable(slice: []const volatile u8) void {
if (!runtime_safety) return;
for (slice) |*byte| _ = byte.*;
}
/// Invokes detectable illegal behavior when the provided array is not aligned
/// to the provided amount.
pub fn assertAligned(ptr: anytype, comptime alignment: std.mem.Alignment) void {
const aligned_ptr: *align(alignment.toByteUnits()) const anyopaque = @ptrCast(@alignCast(ptr));
_ = aligned_ptr;
}
/// Equivalent to `@panic` but with a formatted message.
pub fn panic(comptime format: []const u8, args: anytype) noreturn {
@branchHint(.cold);
panicExtra(@returnAddress(), format, args);
}
/// Equivalent to `@panic` but with a formatted message and an explicitly provided return address
/// which will be the first address in the stack trace.
pub fn panicExtra(
ret_addr: ?usize,
comptime format: []const u8,
args: anytype,
) noreturn {
@branchHint(.cold);
const size = 0x1000;
const trunc_msg = "(msg truncated)";
var buf: [size + trunc_msg.len]u8 = undefined;
var bw: Writer = .fixed(buf[0..size]);
// a minor annoyance with this is that it will result in the NoSpaceLeft
// error being part of the @panic stack trace (but that error should
// only happen rarely)
const msg = if (bw.print(format, args)) |_| bw.buffered() else |_| blk: {
@memcpy(buf[size..], trunc_msg);
break :blk &buf;
};
std.builtin.panic.call(msg, ret_addr);
}
/// Non-zero whenever the program triggered a panic.
/// The counter is incremented/decremented atomically.
var panicking = std.atomic.Value(u8).init(0);
/// Counts how many times the panic handler is invoked by this thread.
/// This is used to catch and handle panics triggered by the panic handler.
threadlocal var panic_stage: usize = 0;
/// For backends that cannot handle the language features depended on by the
/// default panic handler, we will use a simpler implementation.
const use_trap_panic = switch (builtin.zig_backend) {
.stage2_aarch64,
.stage2_arm,
.stage2_powerpc,
.stage2_riscv64,
.stage2_spirv,
.stage2_wasm,
.stage2_x86,
=> true,
else => false,
};
/// Dumps a stack trace to standard error, then aborts.
pub fn defaultPanic(
msg: []const u8,
first_trace_addr: ?usize,
) noreturn {
@branchHint(.cold);
if (use_trap_panic) @trap();
switch (builtin.os.tag) {
.freestanding, .other, .@"3ds", .vita => {
@trap();
},
.uefi => {
const uefi = std.os.uefi;
var utf16_buffer: [1000]u16 = undefined;
const len_minus_3 = std.unicode.utf8ToUtf16Le(&utf16_buffer, msg) catch 0;
utf16_buffer[len_minus_3..][0..3].* = .{ '\r', '\n', 0 };
const len = len_minus_3 + 3;
const exit_msg = utf16_buffer[0 .. len - 1 :0];
// Output to both std_err and con_out, as std_err is easier
// to read in stuff like QEMU at times, but, unlike con_out,
// isn't visible on actual hardware if directly booted into
inline for ([_]?*uefi.protocol.SimpleTextOutput{ uefi.system_table.std_err, uefi.system_table.con_out }) |o| {
if (o) |out| {
out.setAttribute(.{ .foreground = .red }) catch {};
_ = out.outputString(exit_msg) catch {};
out.setAttribute(.{ .foreground = .white }) catch {};
}
}
if (uefi.system_table.boot_services) |bs| {
// ExitData buffer must be allocated using boot_services.allocatePool (spec: page 220)
const exit_data = uefi.raw_pool_allocator.dupeZ(u16, exit_msg) catch @trap();
bs.exit(uefi.handle, .aborted, exit_data) catch {};
}
@trap();
},
.cuda, .amdhsa => std.posix.abort(),
.plan9 => {
var status: [std.os.plan9.ERRMAX]u8 = undefined;
const len = @min(msg.len, status.len - 1);
@memcpy(status[0..len], msg[0..len]);
status[len] = 0;
std.os.plan9.exits(status[0..len :0]);
},
else => {},
}
if (enable_segfault_handler) {
// If a segfault happens while panicking, we want it to actually segfault, not trigger
// the handler.
resetSegfaultHandler();
}
// There is very similar logic to the following in `handleSegfault`.
switch (panic_stage) {
0 => {
panic_stage = 1;
_ = panicking.fetchAdd(1, .seq_cst);
trace: {
const stderr, const tty_config = lockStderrWriter(&.{});
defer unlockStderrWriter();
if (builtin.single_threaded) {
stderr.print("panic: ", .{}) catch break :trace;
} else {
const current_thread_id = std.Thread.getCurrentId();
stderr.print("thread {d} panic: ", .{current_thread_id}) catch break :trace;
}
stderr.print("{s}\n", .{msg}) catch break :trace;
if (@errorReturnTrace()) |t| if (t.index > 0) {
stderr.writeAll("error return context:\n") catch break :trace;
writeStackTrace(t, stderr, tty_config) catch break :trace;
stderr.writeAll("\nstack trace:\n") catch break :trace;
};
writeCurrentStackTrace(.{
.first_address = first_trace_addr orelse @returnAddress(),
.allow_unsafe_unwind = true, // we're crashing anyway, give it our all!
}, stderr, tty_config) catch break :trace;
}
waitForOtherThreadToFinishPanicking();
},
1 => {
panic_stage = 2;
// A panic happened while trying to print a previous panic message.
// We're still holding the mutex but that's fine as we're going to
// call abort().
fs.File.stderr().writeAll("aborting due to recursive panic\n") catch {};
},
else => {}, // Panicked while printing the recursive panic message.
}
posix.abort();
}
/// Must be called only after adding 1 to `panicking`. There are three callsites.
fn waitForOtherThreadToFinishPanicking() void {
if (panicking.fetchSub(1, .seq_cst) != 1) {
// Another thread is panicking, wait for the last one to finish
// and call abort()
if (builtin.single_threaded) unreachable;
// Sleep forever without hammering the CPU
var futex = std.atomic.Value(u32).init(0);
while (true) std.Thread.Futex.wait(&futex, 0);
unreachable;
}
}
pub const StackUnwindOptions = struct {
/// If not `null`, we will ignore all frames up until this return address. This is typically
/// used to omit intermediate handling code (for instance, a panic handler and its machinery)
/// from stack traces.
first_address: ?usize = null,
/// If not `null`, we will unwind from this `cpu_context.Native` instead of the current top of
/// the stack. The main use case here is printing stack traces from signal handlers, where the
/// kernel provides a `*const cpu_context.Native` of the state before the signal.
context: ?CpuContextPtr = null,
/// If `true`, stack unwinding strategies which may cause crashes are used as a last resort.
/// If `false`, only known-safe mechanisms will be attempted.
allow_unsafe_unwind: bool = false,
};
/// Capture and return the current stack trace. The returned `StackTrace` stores its addresses in
/// the given buffer, so `addr_buf` must have a lifetime at least equal to the `StackTrace`.
///
/// See `writeCurrentStackTrace` to immediately print the trace instead of capturing it.
pub noinline fn captureCurrentStackTrace(options: StackUnwindOptions, addr_buf: []usize) StackTrace {
const empty_trace: StackTrace = .{ .index = 0, .instruction_addresses = &.{} };
if (!std.options.allow_stack_tracing) return empty_trace;
var it: StackIterator = .init(options.context);
defer it.deinit();
if (!it.stratOk(options.allow_unsafe_unwind)) return empty_trace;
var total_frames: usize = 0;
var index: usize = 0;
var wait_for = options.first_address;
// Ideally, we would iterate the whole stack so that the `index` in the returned trace was
// indicative of how many frames were skipped. However, this has a significant runtime cost
// in some cases, so at least for now, we don't do that.
while (index < addr_buf.len) switch (it.next()) {
.switch_to_fp => if (!it.stratOk(options.allow_unsafe_unwind)) break,
.end => break,
.frame => |ret_addr| {
if (total_frames > 10_000) {
// Limit the number of frames in case of (e.g.) broken debug information which is
// getting unwinding stuck in a loop.
break;
}
total_frames += 1;
if (wait_for) |target| {
if (ret_addr != target) continue;
wait_for = null;
}
addr_buf[index] = ret_addr;
index += 1;
},
};
return .{
.index = index,
.instruction_addresses = addr_buf[0..index],
};
}
/// Write the current stack trace to `writer`, annotated with source locations.
///
/// See `captureCurrentStackTrace` to capture the trace addresses into a buffer instead of printing.
pub noinline fn writeCurrentStackTrace(options: StackUnwindOptions, writer: *Writer, tty_config: tty.Config) Writer.Error!void {
var threaded: Io.Threaded = .init_single_threaded;
const io = threaded.ioBasic();
if (!std.options.allow_stack_tracing) {
tty_config.setColor(writer, .dim) catch {};
try writer.print("Cannot print stack trace: stack tracing is disabled\n", .{});
tty_config.setColor(writer, .reset) catch {};
return;
}
const di_gpa = getDebugInfoAllocator();
const di = getSelfDebugInfo() catch |err| switch (err) {
error.UnsupportedTarget => {
tty_config.setColor(writer, .dim) catch {};
try writer.print("Cannot print stack trace: debug info unavailable for target\n", .{});
tty_config.setColor(writer, .reset) catch {};
return;
},
};
var it: StackIterator = .init(options.context);
defer it.deinit();
if (!it.stratOk(options.allow_unsafe_unwind)) {
tty_config.setColor(writer, .dim) catch {};
try writer.print("Cannot print stack trace: safe unwind unavailable for target\n", .{});
tty_config.setColor(writer, .reset) catch {};
return;
}
var total_frames: usize = 0;
var wait_for = options.first_address;
var printed_any_frame = false;
while (true) switch (it.next()) {
.switch_to_fp => |unwind_error| {
switch (StackIterator.fp_usability) {
.useless, .unsafe => {},
.safe, .ideal => continue, // no need to even warn
}
const module_name = di.getModuleName(di_gpa, unwind_error.address) catch "???";
const caption: []const u8 = switch (unwind_error.err) {
error.MissingDebugInfo => "unwind info unavailable",
error.InvalidDebugInfo => "unwind info invalid",
error.UnsupportedDebugInfo => "unwind info unsupported",
error.ReadFailed => "filesystem error",
error.OutOfMemory => "out of memory",
error.Canceled => "operation canceled",
error.Unexpected => "unexpected error",
};
if (it.stratOk(options.allow_unsafe_unwind)) {
tty_config.setColor(writer, .dim) catch {};
try writer.print(
"Unwind error at address `{s}:0x{x}` ({s}), remaining frames may be incorrect\n",
.{ module_name, unwind_error.address, caption },
);
tty_config.setColor(writer, .reset) catch {};
} else {
tty_config.setColor(writer, .dim) catch {};
try writer.print(
"Unwind error at address `{s}:0x{x}` ({s}), stopping trace early\n",
.{ module_name, unwind_error.address, caption },
);
tty_config.setColor(writer, .reset) catch {};
return;
}
},
.end => break,
.frame => |ret_addr| {
if (total_frames > 10_000) {
tty_config.setColor(writer, .dim) catch {};
try writer.print(
"Stopping trace after {d} frames (large frame count may indicate broken debug info)\n",
.{total_frames},
);
tty_config.setColor(writer, .reset) catch {};
return;
}
total_frames += 1;
if (wait_for) |target| {
if (ret_addr != target) continue;
wait_for = null;
}
// `ret_addr` is the return address, which is *after* the function call.
// Subtract 1 to get an address *in* the function call for a better source location.
try printSourceAtAddress(di_gpa, io, di, writer, ret_addr -| StackIterator.ra_call_offset, tty_config);
printed_any_frame = true;
},
};
if (!printed_any_frame) return writer.writeAll("(empty stack trace)\n");
}
/// A thin wrapper around `writeCurrentStackTrace` which writes to stderr and ignores write errors.
pub fn dumpCurrentStackTrace(options: StackUnwindOptions) void {
const stderr, const tty_config = lockStderrWriter(&.{});
defer unlockStderrWriter();
writeCurrentStackTrace(.{
.first_address = a: {
if (options.first_address) |a| break :a a;
if (options.context != null) break :a null;
break :a @returnAddress(); // don't include this frame in the trace
},
.context = options.context,
.allow_unsafe_unwind = options.allow_unsafe_unwind,
}, stderr, tty_config) catch |err| switch (err) {
error.WriteFailed => {},
};
}
pub const FormatStackTrace = struct {
stack_trace: StackTrace,
tty_config: tty.Config,
pub fn format(context: @This(), writer: *Io.Writer) Io.Writer.Error!void {
try writer.writeAll("\n");
try writeStackTrace(&context.stack_trace, writer, context.tty_config);
}
};
/// Write a previously captured stack trace to `writer`, annotated with source locations.
pub fn writeStackTrace(st: *const StackTrace, writer: *Writer, tty_config: tty.Config) Writer.Error!void {
if (!std.options.allow_stack_tracing) {
tty_config.setColor(writer, .dim) catch {};
try writer.print("Cannot print stack trace: stack tracing is disabled\n", .{});
tty_config.setColor(writer, .reset) catch {};
return;
}
// We use an independent Io implementation here in case there was a problem
// with the application's Io implementation itself.
var threaded: Io.Threaded = .init_single_threaded;
const io = threaded.ioBasic();
// Fetch `st.index` straight away. Aside from avoiding redundant loads, this prevents issues if
// `st` is `@errorReturnTrace()` and errors are encountered while writing the stack trace.
const n_frames = st.index;
if (n_frames == 0) return writer.writeAll("(empty stack trace)\n");
const di_gpa = getDebugInfoAllocator();
const di = getSelfDebugInfo() catch |err| switch (err) {
error.UnsupportedTarget => {
tty_config.setColor(writer, .dim) catch {};
try writer.print("Cannot print stack trace: debug info unavailable for target\n\n", .{});
tty_config.setColor(writer, .reset) catch {};
return;
},
};
const captured_frames = @min(n_frames, st.instruction_addresses.len);
for (st.instruction_addresses[0..captured_frames]) |ret_addr| {
// `ret_addr` is the return address, which is *after* the function call.
// Subtract 1 to get an address *in* the function call for a better source location.
try printSourceAtAddress(di_gpa, io, di, writer, ret_addr -| StackIterator.ra_call_offset, tty_config);
}
if (n_frames > captured_frames) {
tty_config.setColor(writer, .bold) catch {};
try writer.print("({d} additional stack frames skipped...)\n", .{n_frames - captured_frames});
tty_config.setColor(writer, .reset) catch {};
}
}
/// A thin wrapper around `writeStackTrace` which writes to stderr and ignores write errors.
pub fn dumpStackTrace(st: *const StackTrace) void {
const stderr, const tty_config = lockStderrWriter(&.{});
defer unlockStderrWriter();
writeStackTrace(st, stderr, tty_config) catch |err| switch (err) {
error.WriteFailed => {},
};
}
const StackIterator = union(enum) {
/// We will first report the current PC of this `CpuContextPtr`, then we will switch to a
/// different strategy to actually unwind.
ctx_first: CpuContextPtr,
/// Unwinding using debug info (e.g. DWARF CFI).
di: if (SelfInfo != void and SelfInfo.can_unwind and fp_usability != .ideal)
SelfInfo.UnwindContext
else
noreturn,
/// Naive frame-pointer-based unwinding. Very simple, but typically unreliable.
fp: usize,
/// It is important that this function is marked `inline` so that it can safely use
/// `@frameAddress` and `cpu_context.Native.current` as the caller's stack frame and
/// our own are one and the same.
///
/// `opt_context_ptr` must remain valid while the `StackIterator` is used.
inline fn init(opt_context_ptr: ?CpuContextPtr) StackIterator {
if (opt_context_ptr) |context_ptr| {
// Use `ctx_first` here so we report the PC in the context before unwinding any further.
return .{ .ctx_first = context_ptr };
}
// Otherwise, we're going to capture the current context or frame address, so we don't need
// `ctx_first`, because the first PC is in `std.debug` and we need to unwind before reaching
// a frame we want to report.
// Workaround the C backend being unable to use inline assembly on MSVC by disabling the
// call to `current`. This effectively constrains stack trace collection and dumping to FP
// unwinding when building with CBE for MSVC.
if (!(builtin.zig_backend == .stage2_c and builtin.target.abi == .msvc) and
SelfInfo != void and
SelfInfo.can_unwind and
cpu_context.Native != noreturn and
fp_usability != .ideal)
{
return .{ .di = .init(&.current()) };
}
return .{
// On SPARC, the frame pointer will point to the previous frame's save area,
// meaning we will read the previous return address and thus miss a frame.
// Instead, start at the stack pointer so we get the return address from the
// current frame's save area. The addition of the stack bias cannot fail here
// since we know we have a valid stack pointer.
.fp = if (native_arch.isSPARC()) sp: {
flushSparcWindows();
break :sp asm (""
: [_] "={o6}" (-> usize),
) + stack_bias;
} else @frameAddress(),
};
}
fn deinit(si: *StackIterator) void {
switch (si.*) {
.ctx_first => {},
.fp => {},
.di => |*unwind_context| unwind_context.deinit(getDebugInfoAllocator()),
}
}
noinline fn flushSparcWindows() void {
// Flush all register windows except the current one (hence `noinline`). This ensures that
// we actually see meaningful data on the stack when we walk the frame chain.
if (comptime builtin.target.cpu.has(.sparc, .v9))
asm volatile ("flushw" ::: .{ .memory = true })
else
asm volatile ("ta 3" ::: .{ .memory = true }); // ST_FLUSH_WINDOWS
}
const FpUsability = enum {
/// FP unwinding is impractical on this target. For example, due to its very silly ABI
/// design decisions, it's not possible to do generic FP unwinding on MIPS without a
/// complicated code scanning algorithm.
useless,
/// FP unwinding is unsafe on this target; we may crash when doing so. We will only perform
/// FP unwinding in the case of crashes/panics, or if the user opts in.
unsafe,
/// FP unwinding is guaranteed to be safe on this target. We will do so if unwinding with
/// debug info does not work, and if this compilation has frame pointers enabled.
safe,
/// FP unwinding is the best option on this target. This is usually because the ABI requires
/// a backchain pointer, thus making it always available, safe, and fast.
ideal,
};
const fp_usability: FpUsability = switch (builtin.target.cpu.arch) {
.alpha,
.avr,
.csky,
.microblaze,
.microblazeel,
.mips,
.mipsel,
.mips64,
.mips64el,
.msp430,
.sh,
.sheb,
.xcore,
=> .useless,
.hexagon,
// The PowerPC ABIs don't actually strictly require a backchain pointer; they allow omitting
// it when full unwind info is present. Despite this, both GCC and Clang always enforce the
// presence of the backchain pointer no matter what options they are given. This seems to be
// a case of "the spec is only a polite suggestion", except it works in our favor this time!
.powerpc,
.powerpcle,
.powerpc64,
.powerpc64le,
.sparc,
.sparc64,
=> .ideal,
// https://developer.apple.com/documentation/xcode/writing-arm64-code-for-apple-platforms#Respect-the-purpose-of-specific-CPU-registers
.aarch64 => if (builtin.target.os.tag.isDarwin()) .safe else .unsafe,
else => .unsafe,
};
/// Whether the current unwind strategy is allowed given `allow_unsafe`.
fn stratOk(it: *const StackIterator, allow_unsafe: bool) bool {
return switch (it.*) {
.ctx_first, .di => true,
// If we omitted frame pointers from *this* compilation, FP unwinding would crash
// immediately regardless of anything. But FPs could also be omitted from a different
// linked object, so it's not guaranteed to be safe, unless the target specifically
// requires it.
.fp => switch (fp_usability) {
.useless => false,
.unsafe => allow_unsafe and !builtin.omit_frame_pointer,
.safe => !builtin.omit_frame_pointer,
.ideal => true,
},
};
}
const Result = union(enum) {
/// A stack frame has been found; this is the corresponding return address.
frame: usize,
/// The end of the stack has been reached.
end,
/// We were using `SelfInfo.UnwindInfo`, but are now switching to FP unwinding due to this error.
switch_to_fp: struct {
address: usize,
err: SelfInfoError,
},
};
fn next(it: *StackIterator) Result {
switch (it.*) {
.ctx_first => |context_ptr| {
// After the first frame, start actually unwinding.
it.* = if (SelfInfo != void and SelfInfo.can_unwind and fp_usability != .ideal)
.{ .di = .init(context_ptr) }
else
.{ .fp = context_ptr.getFp() };
// The caller expects *return* addresses, where they will subtract 1 to find the address of the call.
// However, we have the actual current PC, which should not be adjusted. Compensate by adding 1.
return .{ .frame = context_ptr.getPc() +| 1 };
},
.di => |*unwind_context| {
const di = getSelfDebugInfo() catch unreachable;
const di_gpa = getDebugInfoAllocator();
const ret_addr = di.unwindFrame(di_gpa, unwind_context) catch |err| {
const pc = unwind_context.pc;
const fp = unwind_context.getFp();
it.* = .{ .fp = fp };
return .{ .switch_to_fp = .{
.address = pc,
.err = err,
} };
};
if (ret_addr <= 1) return .end;
return .{ .frame = ret_addr };
},
.fp => |fp| {
if (fp == 0) return .end; // we reached the "sentinel" base pointer
const bp_addr = applyOffset(fp, fp_to_bp_offset) orelse return .end;
const ra_addr = applyOffset(fp, fp_to_ra_offset) orelse return .end;
if (bp_addr == 0 or !mem.isAligned(bp_addr, @alignOf(usize)) or
ra_addr == 0 or !mem.isAligned(ra_addr, @alignOf(usize)))
{
// This isn't valid, but it most likely indicates end of stack.
return .end;
}
const bp_ptr: *const usize = @ptrFromInt(bp_addr);
const ra_ptr: *const usize = @ptrFromInt(ra_addr);
const bp = applyOffset(bp_ptr.*, stack_bias) orelse return .end;
// If the stack grows downwards, `bp > fp` should always hold; conversely, if it
// grows upwards, `bp < fp` should always hold. If that is not the case, this
// frame is invalid, so we'll treat it as though we reached end of stack. The
// exception is address 0, which is a graceful end-of-stack signal, in which case
// *this* return address is valid and the *next* iteration will be the last.
if (bp != 0 and switch (comptime builtin.target.stackGrowth()) {
.down => bp <= fp,
.up => bp >= fp,
}) return .end;
it.fp = bp;
const ra = stripInstructionPtrAuthCode(ra_ptr.*);
if (ra <= 1) return .end;
return .{ .frame = ra };
},
}
}
/// Offset of the saved base pointer (previous frame pointer) wrt the frame pointer.
const fp_to_bp_offset = off: {
// On 32-bit PA-RISC, the base pointer is the final word of the frame marker.
if (native_arch == .hppa) break :off -1 * @sizeOf(usize);
// On 64-bit PA-RISC, the frame marker was shrunk significantly; now there's just the return
// address followed by the base pointer.
if (native_arch == .hppa64) break :off -1 * @sizeOf(usize);
// On LoongArch and RISC-V, the frame pointer points to the top of the saved register area,
// in which the base pointer is the first word.
if (native_arch.isLoongArch() or native_arch.isRISCV()) break :off -2 * @sizeOf(usize);
// On OpenRISC, the frame pointer is stored below the return address.
if (native_arch == .or1k) break :off -2 * @sizeOf(usize);
// On SPARC, the frame pointer points to the save area which holds 16 slots for the local
// and incoming registers. The base pointer (i6) is stored in its customary save slot.
if (native_arch.isSPARC()) break :off 14 * @sizeOf(usize);
// Everywhere else, the frame pointer points directly to the location of the base pointer.
break :off 0;
};
/// Offset of the saved return address wrt the frame pointer.
const fp_to_ra_offset = off: {
// On 32-bit PA-RISC, the return address sits in the middle-ish of the frame marker.
if (native_arch == .hppa) break :off -5 * @sizeOf(usize);
// On 64-bit PA-RISC, the frame marker was shrunk significantly; now there's just the return
// address followed by the base pointer.
if (native_arch == .hppa64) break :off -2 * @sizeOf(usize);
// On LoongArch and RISC-V, the frame pointer points to the top of the saved register area,
// in which the return address is the second word.
if (native_arch.isLoongArch() or native_arch.isRISCV()) break :off -1 * @sizeOf(usize);
// On OpenRISC, the return address is stored below the stack parameter area.
if (native_arch == .or1k) break :off -1 * @sizeOf(usize);
if (native_arch.isPowerPC64()) break :off 2 * @sizeOf(usize);
// On s390x, r14 is the link register and we need to grab it from its customary slot in the
// register save area (ELF ABI s390x Supplement §1.2.2.2).
if (native_arch == .s390x) break :off 14 * @sizeOf(usize);
// On SPARC, the frame pointer points to the save area which holds 16 slots for the local
// and incoming registers. The return address (i7) is stored in its customary save slot.
if (native_arch.isSPARC()) break :off 15 * @sizeOf(usize);
break :off @sizeOf(usize);
};
/// Value to add to the stack pointer and frame/base pointers to get the real location being
/// pointed to. Yes, SPARC really does this.
const stack_bias = bias: {
if (native_arch == .sparc64) break :bias 2047;
break :bias 0;
};
/// On some oddball architectures, a return address points to the call instruction rather than
/// the instruction following it.
const ra_call_offset = off: {
if (native_arch.isSPARC()) break :off 0;
break :off 1;
};
fn applyOffset(addr: usize, comptime off: comptime_int) ?usize {
if (off >= 0) return math.add(usize, addr, off) catch return null;
return math.sub(usize, addr, -off) catch return null;
}
};
/// Some platforms use pointer authentication: the upper bits of instruction pointers contain a
/// signature. This function clears those signature bits to make the pointer directly usable.
pub inline fn stripInstructionPtrAuthCode(ptr: usize) usize {
if (native_arch.isAARCH64()) {
// `hint 0x07` maps to `xpaclri` (or `nop` if the hardware doesn't support it)
// The save / restore is because `xpaclri` operates on x30 (LR)
return asm (
\\mov x16, x30
\\mov x30, x15
\\hint 0x07
\\mov x15, x30
\\mov x30, x16
: [ret] "={x15}" (-> usize),
: [ptr] "{x15}" (ptr),
: .{ .x16 = true });
}
return ptr;
}
fn printSourceAtAddress(gpa: Allocator, io: Io, debug_info: *SelfInfo, writer: *Writer, address: usize, tty_config: tty.Config) Writer.Error!void {
const symbol: Symbol = debug_info.getSymbol(gpa, io, address) catch |err| switch (err) {
error.MissingDebugInfo,
error.UnsupportedDebugInfo,
error.InvalidDebugInfo,
=> .unknown,
error.ReadFailed, error.Unexpected, error.Canceled => s: {
tty_config.setColor(writer, .dim) catch {};
try writer.print("Failed to read debug info from filesystem, trace may be incomplete\n\n", .{});
tty_config.setColor(writer, .reset) catch {};
break :s .unknown;
},
error.OutOfMemory => s: {
tty_config.setColor(writer, .dim) catch {};
try writer.print("Ran out of memory loading debug info, trace may be incomplete\n\n", .{});
tty_config.setColor(writer, .reset) catch {};
break :s .unknown;
},
};
defer if (symbol.source_location) |sl| gpa.free(sl.file_name);
return printLineInfo(
writer,
symbol.source_location,
address,
symbol.name orelse "???",
symbol.compile_unit_name orelse debug_info.getModuleName(gpa, address) catch "???",
tty_config,
);
}
fn printLineInfo(
writer: *Writer,
source_location: ?SourceLocation,
address: usize,
symbol_name: []const u8,
compile_unit_name: []const u8,
tty_config: tty.Config,
) Writer.Error!void {
nosuspend {
tty_config.setColor(writer, .bold) catch {};
if (source_location) |*sl| {
try writer.print("{s}:{d}:{d}", .{ sl.file_name, sl.line, sl.column });
} else {
try writer.writeAll("???:?:?");
}
tty_config.setColor(writer, .reset) catch {};
try writer.writeAll(": ");
tty_config.setColor(writer, .dim) catch {};
try writer.print("0x{x} in {s} ({s})", .{ address, symbol_name, compile_unit_name });
tty_config.setColor(writer, .reset) catch {};
try writer.writeAll("\n");
// Show the matching source code line if possible
if (source_location) |sl| {
if (printLineFromFile(writer, sl)) {
if (sl.column > 0) {
// The caret already takes one char
const space_needed = @as(usize, @intCast(sl.column - 1));
try writer.splatByteAll(' ', space_needed);
tty_config.setColor(writer, .green) catch {};
try writer.writeAll("^");
tty_config.setColor(writer, .reset) catch {};
}
try writer.writeAll("\n");
} else |_| {
// Ignore all errors; it's a better UX to just print the source location without the
// corresponding line number. The user can always open the source file themselves.
}
}
}
}
fn printLineFromFile(writer: *Writer, source_location: SourceLocation) !void {
// Allow overriding the target-agnostic source line printing logic by exposing `root.debug.printLineFromFile`.
if (@hasDecl(root, "debug") and @hasDecl(root.debug, "printLineFromFile")) {
return root.debug.printLineFromFile(writer, source_location);
}
// Need this to always block even in async I/O mode, because this could potentially
// be called from e.g. the event loop code crashing.
var f = try fs.cwd().openFile(source_location.file_name, .{});
defer f.close();
// TODO fstat and make sure that the file has the correct size
var buf: [4096]u8 = undefined;
var amt_read = try f.read(buf[0..]);
const line_start = seek: {
var current_line_start: usize = 0;
var next_line: usize = 1;
while (next_line != source_location.line) {
const slice = buf[current_line_start..amt_read];
if (mem.indexOfScalar(u8, slice, '\n')) |pos| {
next_line += 1;
if (pos == slice.len - 1) {
amt_read = try f.read(buf[0..]);
current_line_start = 0;
} else current_line_start += pos + 1;
} else if (amt_read < buf.len) {
return error.EndOfFile;
} else {
amt_read = try f.read(buf[0..]);
current_line_start = 0;
}
}
break :seek current_line_start;
};
const slice = buf[line_start..amt_read];
if (mem.indexOfScalar(u8, slice, '\n')) |pos| {
const line = slice[0 .. pos + 1];
mem.replaceScalar(u8, line, '\t', ' ');
return writer.writeAll(line);
} else { // Line is the last inside the buffer, and requires another read to find delimiter. Alternatively the file ends.
mem.replaceScalar(u8, slice, '\t', ' ');
try writer.writeAll(slice);
while (amt_read == buf.len) {
amt_read = try f.read(buf[0..]);
if (mem.indexOfScalar(u8, buf[0..amt_read], '\n')) |pos| {
const line = buf[0 .. pos + 1];
mem.replaceScalar(u8, line, '\t', ' ');
return writer.writeAll(line);
} else {
const line = buf[0..amt_read];
mem.replaceScalar(u8, line, '\t', ' ');
try writer.writeAll(line);
}
}
// Make sure printing last line of file inserts extra newline
try writer.writeByte('\n');
}
}
test printLineFromFile {
var aw: Writer.Allocating = .init(std.testing.allocator);
defer aw.deinit();
const output_stream = &aw.writer;
const allocator = std.testing.allocator;
const join = std.fs.path.join;
const expectError = std.testing.expectError;
const expectEqualStrings = std.testing.expectEqualStrings;
var test_dir = std.testing.tmpDir(.{});
defer test_dir.cleanup();
// Relies on testing.tmpDir internals which is not ideal, but SourceLocation requires paths.
const test_dir_path = try join(allocator, &.{ ".zig-cache", "tmp", test_dir.sub_path[0..] });
defer allocator.free(test_dir_path);
// Cases
{
const path = try join(allocator, &.{ test_dir_path, "one_line.zig" });
defer allocator.free(path);
try test_dir.dir.writeFile(.{ .sub_path = "one_line.zig", .data = "no new lines in this file, but one is printed anyway" });
try expectError(error.EndOfFile, printLineFromFile(output_stream, .{ .file_name = path, .line = 2, .column = 0 }));
try printLineFromFile(output_stream, .{ .file_name = path, .line = 1, .column = 0 });
try expectEqualStrings("no new lines in this file, but one is printed anyway\n", aw.written());
aw.clearRetainingCapacity();
}
{
const path = try fs.path.join(allocator, &.{ test_dir_path, "three_lines.zig" });
defer allocator.free(path);
try test_dir.dir.writeFile(.{
.sub_path = "three_lines.zig",
.data =
\\1
\\2
\\3
,
});
try printLineFromFile(output_stream, .{ .file_name = path, .line = 1, .column = 0 });
try expectEqualStrings("1\n", aw.written());
aw.clearRetainingCapacity();
try printLineFromFile(output_stream, .{ .file_name = path, .line = 3, .column = 0 });
try expectEqualStrings("3\n", aw.written());
aw.clearRetainingCapacity();
}
{
const file = try test_dir.dir.createFile("line_overlaps_page_boundary.zig", .{});
defer file.close();
const path = try fs.path.join(allocator, &.{ test_dir_path, "line_overlaps_page_boundary.zig" });
defer allocator.free(path);
const overlap = 10;
var buf: [16]u8 = undefined;
var file_writer = file.writer(&buf);
const writer = &file_writer.interface;
try writer.splatByteAll('a', std.heap.page_size_min - overlap);
try writer.writeByte('\n');
try writer.splatByteAll('a', overlap);
try writer.flush();
try printLineFromFile(output_stream, .{ .file_name = path, .line = 2, .column = 0 });
try expectEqualStrings(("a" ** overlap) ++ "\n", aw.written());
aw.clearRetainingCapacity();
}
{
const file = try test_dir.dir.createFile("file_ends_on_page_boundary.zig", .{});
defer file.close();
const path = try fs.path.join(allocator, &.{ test_dir_path, "file_ends_on_page_boundary.zig" });
defer allocator.free(path);
var file_writer = file.writer(&.{});
const writer = &file_writer.interface;
try writer.splatByteAll('a', std.heap.page_size_max);
try printLineFromFile(output_stream, .{ .file_name = path, .line = 1, .column = 0 });
try expectEqualStrings(("a" ** std.heap.page_size_max) ++ "\n", aw.written());
aw.clearRetainingCapacity();
}
{
const file = try test_dir.dir.createFile("very_long_first_line_spanning_multiple_pages.zig", .{});
defer file.close();
const path = try fs.path.join(allocator, &.{ test_dir_path, "very_long_first_line_spanning_multiple_pages.zig" });
defer allocator.free(path);
var file_writer = file.writer(&.{});
const writer = &file_writer.interface;
try writer.splatByteAll('a', 3 * std.heap.page_size_max);
try expectError(error.EndOfFile, printLineFromFile(output_stream, .{ .file_name = path, .line = 2, .column = 0 }));
try printLineFromFile(output_stream, .{ .file_name = path, .line = 1, .column = 0 });
try expectEqualStrings(("a" ** (3 * std.heap.page_size_max)) ++ "\n", aw.written());
aw.clearRetainingCapacity();
try writer.writeAll("a\na");
try printLineFromFile(output_stream, .{ .file_name = path, .line = 1, .column = 0 });
try expectEqualStrings(("a" ** (3 * std.heap.page_size_max)) ++ "a\n", aw.written());
aw.clearRetainingCapacity();
try printLineFromFile(output_stream, .{ .file_name = path, .line = 2, .column = 0 });
try expectEqualStrings("a\n", aw.written());
aw.clearRetainingCapacity();
}
{
const file = try test_dir.dir.createFile("file_of_newlines.zig", .{});
defer file.close();
const path = try fs.path.join(allocator, &.{ test_dir_path, "file_of_newlines.zig" });
defer allocator.free(path);
var file_writer = file.writer(&.{});
const writer = &file_writer.interface;
const real_file_start = 3 * std.heap.page_size_min;
try writer.splatByteAll('\n', real_file_start);
try writer.writeAll("abc\ndef");
try printLineFromFile(output_stream, .{ .file_name = path, .line = real_file_start + 1, .column = 0 });
try expectEqualStrings("abc\n", aw.written());
aw.clearRetainingCapacity();
try printLineFromFile(output_stream, .{ .file_name = path, .line = real_file_start + 2, .column = 0 });
try expectEqualStrings("def\n", aw.written());
aw.clearRetainingCapacity();
}
}
/// The returned allocator should be thread-safe if the compilation is multi-threaded, because
/// multiple threads could capture and/or print stack traces simultaneously.
fn getDebugInfoAllocator() Allocator {
// Allow overriding the debug info allocator by exposing `root.debug.getDebugInfoAllocator`.
if (@hasDecl(root, "debug") and @hasDecl(root.debug, "getDebugInfoAllocator")) {
return root.debug.getDebugInfoAllocator();
}
// Otherwise, use a global arena backed by the page allocator
const S = struct {
var arena: std.heap.ArenaAllocator = .init(std.heap.page_allocator);
var ts_arena: std.heap.ThreadSafeAllocator = .{ .child_allocator = arena.allocator() };
};
return S.ts_arena.allocator();
}
/// Whether or not the current target can print useful debug information when a segfault occurs.
pub const have_segfault_handling_support = switch (native_os) {
.haiku,
.linux,
.serenity,
.dragonfly,
.freebsd,
.netbsd,
.openbsd,
.driverkit,
.ios,
.maccatalyst,
.macos,
.tvos,
.visionos,
.watchos,
.illumos,
.windows,
=> true,
else => false,
};
const enable_segfault_handler = std.options.enable_segfault_handler;
pub const default_enable_segfault_handler = runtime_safety and have_segfault_handling_support;
pub fn maybeEnableSegfaultHandler() void {
if (enable_segfault_handler) {
attachSegfaultHandler();
}
}
var windows_segfault_handle: ?windows.HANDLE = null;
pub fn updateSegfaultHandler(act: ?*const posix.Sigaction) void {
posix.sigaction(.SEGV, act, null);
posix.sigaction(.ILL, act, null);
posix.sigaction(.BUS, act, null);
posix.sigaction(.FPE, act, null);
}
/// Attaches a global handler for several signals which, when triggered, prints output to stderr
/// similar to the default panic handler, with a message containing the type of signal and a stack
/// trace if possible. This implementation does not just call the panic handler, because unwinding
/// the stack (for a stack trace) when a signal is received requires special target-specific logic.
///
/// The signals for which a handler is installed are:
/// * SIGSEGV (segmentation fault)
/// * SIGILL (illegal instruction)
/// * SIGBUS (bus error)
/// * SIGFPE (arithmetic exception)
pub fn attachSegfaultHandler() void {
if (!have_segfault_handling_support) {
@compileError("segfault handler not supported for this target");
}
if (native_os == .windows) {
windows_segfault_handle = windows.ntdll.RtlAddVectoredExceptionHandler(0, handleSegfaultWindows);
return;
}
const act = posix.Sigaction{
.handler = .{ .sigaction = handleSegfaultPosix },
.mask = posix.sigemptyset(),
.flags = (posix.SA.SIGINFO | posix.SA.RESTART | posix.SA.RESETHAND),
};
updateSegfaultHandler(&act);
}
fn resetSegfaultHandler() void {
if (native_os == .windows) {
if (windows_segfault_handle) |handle| {
assert(windows.ntdll.RtlRemoveVectoredExceptionHandler(handle) != 0);
windows_segfault_handle = null;
}
return;
}
const act = posix.Sigaction{
.handler = .{ .handler = posix.SIG.DFL },
.mask = posix.sigemptyset(),
.flags = 0,
};
updateSegfaultHandler(&act);
}
fn handleSegfaultPosix(sig: posix.SIG, info: *const posix.siginfo_t, ctx_ptr: ?*anyopaque) callconv(.c) noreturn {
if (use_trap_panic) @trap();
const addr: ?usize, const name: []const u8 = info: {
if (native_os == .linux and native_arch == .x86_64) {
// x86_64 doesn't have a full 64-bit virtual address space.
// Addresses outside of that address space are non-canonical
// and the CPU won't provide the faulting address to us.
// This happens when accessing memory addresses such as 0xaaaaaaaaaaaaaaaa
// but can also happen when no addressable memory is involved;
// for example when reading/writing model-specific registers
// by executing `rdmsr` or `wrmsr` in user-space (unprivileged mode).
const SI_KERNEL = 0x80;
if (sig == .SEGV and info.code == SI_KERNEL) {
break :info .{ null, "General protection exception" };
}
}
const addr: usize = switch (native_os) {
.serenity,
.dragonfly,
.freebsd,
.driverkit,
.ios,
.maccatalyst,
.macos,
.tvos,
.visionos,
.watchos,
=> @intFromPtr(info.addr),
.linux,
=> @intFromPtr(info.fields.sigfault.addr),
.netbsd,
=> @intFromPtr(info.info.reason.fault.addr),
.haiku,
.openbsd,
=> @intFromPtr(info.data.fault.addr),
.illumos,
=> @intFromPtr(info.reason.fault.addr),
else => comptime unreachable,
};
const name = switch (sig) {
.SEGV => "Segmentation fault",
.ILL => "Illegal instruction",
.BUS => "Bus error",
.FPE => "Arithmetic exception",
else => unreachable,
};
break :info .{ addr, name };
};
const opt_cpu_context: ?cpu_context.Native = cpu_context.fromPosixSignalContext(ctx_ptr);
if (native_arch.isSPARC()) {
// It's unclear to me whether this is a QEMU bug or also real kernel behavior, but in the
// former, I observed that the most recent register window wasn't getting spilled on the
// stack as expected when a signal arrived. A `flushw` from the signal handler does not
// appear to be sufficient either. On the other hand, when doing a synchronous stack trace
// and using `flushw`, this all appears to work as expected. So, *probably* a QEMU bug, but
// someone with real SPARC hardware should verify.
//
// In any case, the register save area exists specifically so that register windows can be
// spilled asynchronously. This means that it should be perfectly fine for us to manually do
// so here.
const ctx = opt_cpu_context.?;
@as(*[16]usize, @ptrFromInt(ctx.o[6] + StackIterator.stack_bias)).* = ctx.l ++ ctx.i;
}
handleSegfault(addr, name, if (opt_cpu_context) |*ctx| ctx else null);
}
fn handleSegfaultWindows(info: *windows.EXCEPTION_POINTERS) callconv(.winapi) c_long {
if (use_trap_panic) @trap();
const name: []const u8, const addr: ?usize = switch (info.ExceptionRecord.ExceptionCode) {
windows.EXCEPTION_DATATYPE_MISALIGNMENT => .{ "Unaligned memory access", null },
windows.EXCEPTION_ACCESS_VIOLATION => .{ "Segmentation fault", info.ExceptionRecord.ExceptionInformation[1] },
windows.EXCEPTION_ILLEGAL_INSTRUCTION => .{ "Illegal instruction", info.ContextRecord.getRegs().ip },
windows.EXCEPTION_STACK_OVERFLOW => .{ "Stack overflow", null },
else => return windows.EXCEPTION_CONTINUE_SEARCH,
};
handleSegfault(addr, name, &cpu_context.fromWindowsContext(info.ContextRecord));
}
fn handleSegfault(addr: ?usize, name: []const u8, opt_ctx: ?CpuContextPtr) noreturn {
// Allow overriding the target-agnostic segfault handler by exposing `root.debug.handleSegfault`.
if (@hasDecl(root, "debug") and @hasDecl(root.debug, "handleSegfault")) {
return root.debug.handleSegfault(addr, name, opt_ctx);
}
return defaultHandleSegfault(addr, name, opt_ctx);
}
pub fn defaultHandleSegfault(addr: ?usize, name: []const u8, opt_ctx: ?CpuContextPtr) noreturn {
// There is very similar logic to the following in `defaultPanic`.
switch (panic_stage) {
0 => {
panic_stage = 1;
_ = panicking.fetchAdd(1, .seq_cst);
trace: {
const stderr, const tty_config = lockStderrWriter(&.{});
defer unlockStderrWriter();
if (addr) |a| {
stderr.print("{s} at address 0x{x}\n", .{ name, a }) catch break :trace;
} else {
stderr.print("{s} (no address available)\n", .{name}) catch break :trace;
}
if (opt_ctx) |context| {
writeCurrentStackTrace(.{
.context = context,
.allow_unsafe_unwind = true, // we're crashing anyway, give it our all!
}, stderr, tty_config) catch break :trace;
}
}
},
1 => {
panic_stage = 2;
// A segfault happened while trying to print a previous panic message.
// We're still holding the mutex but that's fine as we're going to
// call abort().
fs.File.stderr().writeAll("aborting due to recursive panic\n") catch {};
},
else => {}, // Panicked while printing the recursive panic message.
}
// We cannot allow the signal handler to return because when it runs the original instruction
// again, the memory may be mapped and undefined behavior would occur rather than repeating
// the segfault. So we simply abort here.
posix.abort();
}
pub fn dumpStackPointerAddr(prefix: []const u8) void {
const sp = asm (""
: [argc] "={rsp}" (-> usize),
);
print("{s} sp = 0x{x}\n", .{ prefix, sp });
}
test "manage resources correctly" {
if (SelfInfo == void) return error.SkipZigTest;
const S = struct {
noinline fn showMyTrace() usize {
return @returnAddress();
}
};
const gpa = std.testing.allocator;
var threaded: Io.Threaded = .init_single_threaded;
const io = threaded.ioBasic();
var discarding: Io.Writer.Discarding = .init(&.{});
var di: SelfInfo = .init;
defer di.deinit(gpa);
try printSourceAtAddress(
gpa,
io,
&di,
&discarding.writer,
S.showMyTrace(),
.no_color,
);
}
/// This API helps you track where a value originated and where it was mutated,
/// or any other points of interest.
/// In debug mode, it adds a small size penalty (104 bytes on 64-bit architectures)
/// to the aggregate that you add it to.
/// In release mode, it is size 0 and all methods are no-ops.
/// This is a pre-made type with default settings.
/// For more advanced usage, see `ConfigurableTrace`.
pub const Trace = ConfigurableTrace(2, 4, builtin.mode == .Debug);
pub fn ConfigurableTrace(comptime size: usize, comptime stack_frame_count: usize, comptime is_enabled: bool) type {
return struct {
addrs: [actual_size][stack_frame_count]usize,
notes: [actual_size][]const u8,
index: Index,
const actual_size = if (enabled) size else 0;
const Index = if (enabled) usize else u0;
pub const init: @This() = .{
.addrs = undefined,
.notes = undefined,
.index = 0,
};
pub const enabled = is_enabled;
pub const add = if (enabled) addNoInline else addNoOp;
pub noinline fn addNoInline(t: *@This(), note: []const u8) void {
comptime assert(enabled);
return addAddr(t, @returnAddress(), note);
}
pub inline fn addNoOp(t: *@This(), note: []const u8) void {
_ = t;
_ = note;
comptime assert(!enabled);
}
pub fn addAddr(t: *@This(), addr: usize, note: []const u8) void {
if (!enabled) return;
if (t.index < size) {
t.notes[t.index] = note;
const addrs = &t.addrs[t.index];
const st = captureCurrentStackTrace(.{ .first_address = addr }, addrs);
if (st.index < addrs.len) {
@memset(addrs[st.index..], 0); // zero unused frames to indicate end of trace
}
}
// Keep counting even if the end is reached so that the
// user can find out how much more size they need.
t.index += 1;
}
pub fn dump(t: @This()) void {
if (!enabled) return;
const stderr, const tty_config = lockStderrWriter(&.{});
defer unlockStderrWriter();
const end = @min(t.index, size);
for (t.addrs[0..end], 0..) |frames_array, i| {
stderr.print("{s}:\n", .{t.notes[i]}) catch return;
var frames_array_mutable = frames_array;
const frames = mem.sliceTo(frames_array_mutable[0..], 0);
const stack_trace: StackTrace = .{
.index = frames.len,
.instruction_addresses = frames,
};
writeStackTrace(&stack_trace, stderr, tty_config) catch return;
}
if (t.index > end) {
stderr.print("{d} more traces not shown; consider increasing trace size\n", .{
t.index - end,
}) catch return;
}
}
pub fn format(
t: @This(),
comptime fmt: []const u8,
options: std.fmt.Options,
writer: *Writer,
) !void {
if (fmt.len != 0) std.fmt.invalidFmtError(fmt, t);
_ = options;
if (enabled) {
try writer.writeAll("\n");
t.dump();
try writer.writeAll("\n");
} else {
return writer.writeAll("(value tracing disabled)");
}
}
};
}
pub const SafetyLock = struct {
state: State = if (runtime_safety) .unlocked else .unknown,
pub const State = if (runtime_safety) enum { unlocked, locked } else enum { unknown };
pub fn lock(l: *SafetyLock) void {
if (!runtime_safety) return;
assert(l.state == .unlocked);
l.state = .locked;
}
pub fn unlock(l: *SafetyLock) void {
if (!runtime_safety) return;
assert(l.state == .locked);
l.state = .unlocked;
}
pub fn assertUnlocked(l: SafetyLock) void {
if (!runtime_safety) return;
assert(l.state == .unlocked);
}
pub fn assertLocked(l: SafetyLock) void {
if (!runtime_safety) return;
assert(l.state == .locked);
}
};
test SafetyLock {
var safety_lock: SafetyLock = .{};
safety_lock.assertUnlocked();
safety_lock.lock();
safety_lock.assertLocked();
safety_lock.unlock();
safety_lock.assertUnlocked();
}
/// Detect whether the program is being executed in the Valgrind virtual machine.
///
/// When Valgrind integrations are disabled, this returns comptime-known false.
/// Otherwise, the result is runtime-known.
pub inline fn inValgrind() bool {
if (@inComptime()) return false;
if (!builtin.valgrind_support) return false;
return std.valgrind.runningOnValgrind() > 0;
}
test {
_ = &Dwarf;
_ = &Pdb;
_ = &SelfInfo;
_ = &dumpHex;
}