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FailingAllocator: remove outdated doc comments, move doc comment example to decltest

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Note: The decltests for files-as-a-struct don't show up in autodoc currently
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Ryan Liptak 2025-04-19 15:37:08 -07:00 • committed by Andrew Kelley
parent 927f233ff8
commit c06fecd466
1 changed files with 38 additions and 14 deletions
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52
lib/std/testing/FailingAllocator.zig
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@ -1,13 +1,5 @@
//! Allocator that fails after N allocations, useful for making sure out of
//! memory conditions are handled correctly.
//!
//! To use this, first initialize it and get an allocator with
//!
//! `const failing_allocator = &FailingAllocator.init(<allocator>,
//! <config>).allocator;`
//!
//! Then use `failing_allocator` anywhere you would have used a
//! different allocator.
const std = @import("../std.zig");
const mem = std.mem;
const FailingAllocator = @This();
@ -28,12 +20,7 @@ const num_stack_frames = if (std.debug.sys_can_stack_trace) 16 else 0;
pub const Config = struct {
/// The number of successful allocations you can expect from this allocator.
/// The next allocation will fail. For example, with `fail_index` equal to
/// 2, the following test will pass:
///
/// var a = try failing_alloc.create(i32);
/// var b = try failing_alloc.create(i32);
/// testing.expectError(error.OutOfMemory, failing_alloc.create(i32));
/// The next allocation will fail.
fail_index: usize = std.math.maxInt(usize),
/// Number of successful resizes to expect from this allocator. The next resize will fail.
@ -159,3 +146,40 @@ pub fn getStackTrace(self: *FailingAllocator) std.builtin.StackTrace {
.index = len,
};
}
test FailingAllocator {
// Fail on allocation
{
var failing_allocator_state = FailingAllocator.init(std.testing.allocator, .{
.fail_index = 2,
});
const failing_alloc = failing_allocator_state.allocator();
const a = try failing_alloc.create(i32);
defer failing_alloc.destroy(a);
const b = try failing_alloc.create(i32);
defer failing_alloc.destroy(b);
try std.testing.expectError(error.OutOfMemory, failing_alloc.create(i32));
}
// Fail on resize
{
var failing_allocator_state = FailingAllocator.init(std.testing.allocator, .{
.resize_fail_index = 1,
});
const failing_alloc = failing_allocator_state.allocator();
const resized_slice = blk: {
const slice = try failing_alloc.alloc(u8, 8);
errdefer failing_alloc.free(slice);
break :blk failing_alloc.remap(slice, 6) orelse return error.UnexpectedRemapFailure;
};
defer failing_alloc.free(resized_slice);
// Remap and resize should fail from here on out
try std.testing.expectEqual(null, failing_alloc.remap(resized_slice, 4));
try std.testing.expectEqual(false, failing_alloc.resize(resized_slice, 4));
// Note: realloc could succeed because it falls back to free+alloc
}
}