Merge pull request #25191 from ziglang/fix-linker-undef-memory

fix linker writing undefined memory to output file

lib/std/Io/Writer.zig

@@ -865,6 +865,11 @@ pub inline fn writeSliceEndian(
     slice: []const Elem,
     endian: std.builtin.Endian,
 ) Error!void {
+    switch (@typeInfo(Elem)) {
+        .@"struct" => |info| comptime assert(info.layout != .auto),
+        .int, .@"enum" => {},
+        else => @compileError("ill-defined memory layout"),
+    }
     if (native_endian == endian) {
         return writeAll(w, @ptrCast(slice));
     } else {

src/link/Coff.zig

@@ -1,4 +1,38 @@
 //! The main driver of the self-hosted COFF linker.
+const Coff = @This();
+
+const std = @import("std");
+const build_options = @import("build_options");
+const builtin = @import("builtin");
+const assert = std.debug.assert;
+const coff_util = std.coff;
+const fmt = std.fmt;
+const fs = std.fs;
+const log = std.log.scoped(.link);
+const math = std.math;
+const mem = std.mem;
+
+const Allocator = std.mem.Allocator;
+const Path = std.Build.Cache.Path;
+const Directory = std.Build.Cache.Directory;
+const Cache = std.Build.Cache;
+
+const aarch64_util = link.aarch64;
+const allocPrint = std.fmt.allocPrint;
+const codegen = @import("../codegen.zig");
+const link = @import("../link.zig");
+const target_util = @import("../target.zig");
+const trace = @import("../tracy.zig").trace;
+
+const Compilation = @import("../Compilation.zig");
+const Zcu = @import("../Zcu.zig");
+const InternPool = @import("../InternPool.zig");
+const TableSection = @import("table_section.zig").TableSection;
+const StringTable = @import("StringTable.zig");
+const Type = @import("../Type.zig");
+const Value = @import("../Value.zig");
+const AnalUnit = InternPool.AnalUnit;
+const dev = @import("../dev.zig");
 
 base: link.File,
 image_base: u64,
@@ -2168,12 +2202,12 @@ fn writeStrtab(coff: *Coff) !void {
 
 fn writeSectionHeaders(coff: *Coff) !void {
     const offset = coff.getSectionHeadersOffset();
-    try coff.pwriteAll(mem.sliceAsBytes(coff.sections.items(.header)), offset);
+    try coff.pwriteAll(@ptrCast(coff.sections.items(.header)), offset);
 }
 
 fn writeDataDirectoriesHeaders(coff: *Coff) !void {
     const offset = coff.getDataDirectoryHeadersOffset();
-    try coff.pwriteAll(mem.sliceAsBytes(&coff.data_directories), offset);
+    try coff.pwriteAll(@ptrCast(&coff.data_directories), offset);
 }
 
 fn writeHeader(coff: *Coff) !void {
@@ -3068,41 +3102,6 @@ fn pwriteAll(coff: *Coff, bytes: []const u8, offset: u64) error{LinkFailure}!voi
     };
 }
 
-const Coff = @This();
-
-const std = @import("std");
-const build_options = @import("build_options");
-const builtin = @import("builtin");
-const assert = std.debug.assert;
-const coff_util = std.coff;
-const fmt = std.fmt;
-const fs = std.fs;
-const log = std.log.scoped(.link);
-const math = std.math;
-const mem = std.mem;
-
-const Allocator = std.mem.Allocator;
-const Path = std.Build.Cache.Path;
-const Directory = std.Build.Cache.Directory;
-const Cache = std.Build.Cache;
-
-const aarch64_util = link.aarch64;
-const allocPrint = std.fmt.allocPrint;
-const codegen = @import("../codegen.zig");
-const link = @import("../link.zig");
-const target_util = @import("../target.zig");
-const trace = @import("../tracy.zig").trace;
-
-const Compilation = @import("../Compilation.zig");
-const Zcu = @import("../Zcu.zig");
-const InternPool = @import("../InternPool.zig");
-const TableSection = @import("table_section.zig").TableSection;
-const StringTable = @import("StringTable.zig");
-const Type = @import("../Type.zig");
-const Value = @import("../Value.zig");
-const AnalUnit = InternPool.AnalUnit;
-const dev = @import("../dev.zig");
-
 /// This is the start of a Portable Executable (PE) file.
 /// It starts with a MS-DOS header followed by a MS-DOS stub program.
 /// This data does not change so we include it as follows in all binaries.

src/link/Elf.zig

@@ -1465,7 +1465,7 @@ pub fn writeShdrTable(self: *Elf) !void {
                     mem.byteSwapAllFields(elf.Elf32_Shdr, shdr);
                 }
             }
-            try self.pwriteAll(mem.sliceAsBytes(buf), self.shdr_table_offset.?);
+            try self.pwriteAll(@ptrCast(buf), self.shdr_table_offset.?);
         },
         .p64 => {
             const buf = try gpa.alloc(elf.Elf64_Shdr, self.sections.items(.shdr).len);
@@ -1478,7 +1478,7 @@ pub fn writeShdrTable(self: *Elf) !void {
                     mem.byteSwapAllFields(elf.Elf64_Shdr, shdr);
                 }
             }
-            try self.pwriteAll(mem.sliceAsBytes(buf), self.shdr_table_offset.?);
+            try self.pwriteAll(@ptrCast(buf), self.shdr_table_offset.?);
         },
     }
 }
@@ -1505,7 +1505,7 @@ fn writePhdrTable(self: *Elf) !void {
                     mem.byteSwapAllFields(elf.Elf32_Phdr, phdr);
                 }
             }
-            try self.pwriteAll(mem.sliceAsBytes(buf), phdr_table.p_offset);
+            try self.pwriteAll(@ptrCast(buf), phdr_table.p_offset);
         },
         .p64 => {
             const buf = try gpa.alloc(elf.Elf64_Phdr, self.phdrs.items.len);
@@ -1517,7 +1517,7 @@ fn writePhdrTable(self: *Elf) !void {
                     mem.byteSwapAllFields(elf.Elf64_Phdr, phdr);
                 }
             }
-            try self.pwriteAll(mem.sliceAsBytes(buf), phdr_table.p_offset);
+            try self.pwriteAll(@ptrCast(buf), phdr_table.p_offset);
         },
     }
 }
@@ -3157,7 +3157,7 @@ fn writeSyntheticSections(self: *Elf) !void {
 
     if (self.section_indexes.versym) |shndx| {
         const shdr = slice.items(.shdr)[shndx];
-        try self.pwriteAll(mem.sliceAsBytes(self.versym.items), shdr.sh_offset);
+        try self.pwriteAll(@ptrCast(self.versym.items), shdr.sh_offset);
     }
 
     if (self.section_indexes.verneed) |shndx| {
@@ -3226,7 +3226,7 @@ fn writeSyntheticSections(self: *Elf) !void {
         try self.got.addRela(self);
         try self.copy_rel.addRela(self);
         self.sortRelaDyn();
-        try self.pwriteAll(mem.sliceAsBytes(self.rela_dyn.items), shdr.sh_offset);
+        try self.pwriteAll(@ptrCast(self.rela_dyn.items), shdr.sh_offset);
     }
 
     if (self.section_indexes.plt) |shndx| {
@@ -3256,7 +3256,7 @@ fn writeSyntheticSections(self: *Elf) !void {
     if (self.section_indexes.rela_plt) |shndx| {
         const shdr = slice.items(.shdr)[shndx];
         try self.plt.addRela(self);
-        try self.pwriteAll(mem.sliceAsBytes(self.rela_plt.items), shdr.sh_offset);
+        try self.pwriteAll(@ptrCast(self.rela_plt.items), shdr.sh_offset);
     }
 
     try self.writeSymtab();
@@ -3364,13 +3364,13 @@ pub fn writeSymtab(self: *Elf) !void {
                 };
                 if (foreign_endian) mem.byteSwapAllFields(elf.Elf32_Sym, out);
             }
-            try self.pwriteAll(mem.sliceAsBytes(buf), symtab_shdr.sh_offset);
+            try self.pwriteAll(@ptrCast(buf), symtab_shdr.sh_offset);
         },
         .p64 => {
             if (foreign_endian) {
                 for (self.symtab.items) |*sym| mem.byteSwapAllFields(elf.Elf64_Sym, sym);
             }
-            try self.pwriteAll(mem.sliceAsBytes(self.symtab.items), symtab_shdr.sh_offset);
+            try self.pwriteAll(@ptrCast(self.symtab.items), symtab_shdr.sh_offset);
         },
     }
 

src/link/Elf/eh_frame.zig

@@ -482,7 +482,7 @@ pub fn writeEhFrameHdr(elf_file: *Elf, writer: anytype) !void {
     );
     try writer.writeInt(u32, num_fdes, .little);
 
-    const Entry = struct {
+    const Entry = extern struct {
         init_addr: u32,
         fde_addr: u32,
 
@@ -520,7 +520,7 @@ pub fn writeEhFrameHdr(elf_file: *Elf, writer: anytype) !void {
     }
 
     std.mem.sort(Entry, entries.items, {}, Entry.lessThan);
-    try writer.writeAll(std.mem.sliceAsBytes(entries.items));
+    try writer.writeSliceEndian(Entry, entries.items, .little);
 }
 
 const eh_frame_hdr_header_size: usize = 12;

src/link/Elf/relocatable.zig

@@ -397,7 +397,7 @@ fn writeSyntheticSections(elf_file: *Elf) !void {
             shdr.sh_offset + shdr.sh_size,
         });
 
-        try elf_file.base.file.?.pwriteAll(mem.sliceAsBytes(relocs.items), shdr.sh_offset);
+        try elf_file.base.file.?.pwriteAll(@ptrCast(relocs.items), shdr.sh_offset);
     }
 
     if (elf_file.section_indexes.eh_frame) |shndx| {
@@ -435,7 +435,7 @@ fn writeSyntheticSections(elf_file: *Elf) !void {
             shdr.sh_offset,
             shdr.sh_offset + shdr.sh_size,
         });
-        try elf_file.base.file.?.pwriteAll(mem.sliceAsBytes(relocs.items), shdr.sh_offset);
+        try elf_file.base.file.?.pwriteAll(@ptrCast(relocs.items), shdr.sh_offset);
     }
 
     try writeGroups(elf_file);

src/link/Elf/synthetic_sections.zig

@@ -1265,7 +1265,7 @@ pub const GnuHashSection = struct {
             bloom[idx] |= @as(u64, 1) << @as(u6, @intCast((h >> bloom_shift) % 64));
         }
 
-        try writer.writeAll(mem.sliceAsBytes(bloom));
+        try writer.writeSliceEndian(u64, bloom, .little);
 
         // Fill in the hash bucket indices
         const buckets = try gpa.alloc(u32, hash.num_buckets);
@@ -1278,7 +1278,7 @@ pub const GnuHashSection = struct {
             }
         }
 
-        try writer.writeAll(mem.sliceAsBytes(buckets));
+        try writer.writeSliceEndian(u32, buckets, .little);
 
         // Finally, write the hash table
         const table = try gpa.alloc(u32, hash.num_exports);
@@ -1294,7 +1294,7 @@ pub const GnuHashSection = struct {
             }
         }
 
-        try writer.writeAll(mem.sliceAsBytes(table));
+        try writer.writeSliceEndian(u32, table, .little);
     }
 
     pub fn hasher(name: [:0]const u8) u32 {
@@ -1442,8 +1442,8 @@ pub const VerneedSection = struct {
     }
 
     pub fn write(vern: VerneedSection, writer: *std.Io.Writer) !void {
-        try writer.writeAll(mem.sliceAsBytes(vern.verneed.items));
+        try writer.writeSliceEndian(elf.Elf64_Verneed, vern.verneed.items, .little);
-        try writer.writeAll(mem.sliceAsBytes(vern.vernaux.items));
+        try writer.writeSliceEndian(elf.Vernaux, vern.vernaux.items, .little);
     }
 };
 

src/link/MachO.zig

@@ -2711,7 +2711,7 @@ pub fn writeSymtabToFile(self: *MachO) !void {
     const tracy = trace(@src());
     defer tracy.end();
     const cmd = self.symtab_cmd;
-    try self.pwriteAll(mem.sliceAsBytes(self.symtab.items), cmd.symoff);
+    try self.pwriteAll(@ptrCast(self.symtab.items), cmd.symoff);
     try self.pwriteAll(self.strtab.items, cmd.stroff);
 }
 

src/link/MachO/DebugSymbols.zig

@@ -403,7 +403,7 @@ pub fn writeSymtab(self: *DebugSymbols, off: u32, macho_file: *MachO) !u32 {
         internal.writeSymtab(macho_file, self);
     }
 
-    try self.file.?.pwriteAll(mem.sliceAsBytes(self.symtab.items), cmd.symoff);
+    try self.file.?.pwriteAll(@ptrCast(self.symtab.items), cmd.symoff);
 
     return off + cmd.nsyms * @sizeOf(macho.nlist_64);
 }

src/link/MachO/UnwindInfo.zig

@@ -311,7 +311,7 @@ pub fn write(info: UnwindInfo, macho_file: *MachO, buffer: []u8) !void {
         .indexCount = indexes_count,
     }), .little);
 
-    try writer.writeAll(mem.sliceAsBytes(info.common_encodings[0..info.common_encodings_count]));
+    try writer.writeSliceEndian(Encoding, info.common_encodings[0..info.common_encodings_count], .little);
 
     for (info.personalities[0..info.personalities_count]) |ref| {
         const sym = ref.getSymbol(macho_file).?;

src/link/MachO/relocatable.zig

@@ -676,11 +676,11 @@ fn writeSectionsToFile(macho_file: *MachO) !void {
     const slice = macho_file.sections.slice();
     for (slice.items(.header), slice.items(.out), slice.items(.relocs)) |header, out, relocs| {
         try macho_file.pwriteAll(out.items, header.offset);
-        try macho_file.pwriteAll(mem.sliceAsBytes(relocs.items), header.reloff);
+        try macho_file.pwriteAll(@ptrCast(relocs.items), header.reloff);
     }
 
     try macho_file.writeDataInCode();
-    try macho_file.pwriteAll(mem.sliceAsBytes(macho_file.symtab.items), macho_file.symtab_cmd.symoff);
+    try macho_file.pwriteAll(@ptrCast(macho_file.symtab.items), macho_file.symtab_cmd.symoff);
     try macho_file.pwriteAll(macho_file.strtab.items, macho_file.symtab_cmd.stroff);
 }
 

src/link/SpirV.zig

@@ -285,7 +285,8 @@ pub fn flush(
         else => |other| return diags.fail("error while linking: {s}", .{@errorName(other)}),
     };
 
-    linker.base.file.?.writeAll(std.mem.sliceAsBytes(linked_module)) catch |err|
+    // TODO endianness bug. use file writer and call writeSliceEndian instead
+    linker.base.file.?.writeAll(@ptrCast(linked_module)) catch |err|
         return diags.fail("failed to write: {s}", .{@errorName(err)});
 }