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zig libc malloc: set errno when returning null

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This commit is contained in:
Andrew Kelley 2026-02-11 23:49:21 -08:00
parent 0de7668c01
commit ec02571a30
1 changed files with 21 additions and 11 deletions
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32
lib/c/malloc.zig
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@ -64,9 +64,9 @@ const Header = packed struct(u64) {
};
fn malloc(n: usize) callconv(.c) ?[*]align(alignment_bytes) u8 {
const size = std.math.cast(Header.Size, n) orelse return null;
const size = std.math.cast(Header.Size, n) orelse return nomem();
const ptr: [*]align(alignment_bytes) u8 = @alignCast(
vtable.alloc(no_context, n + alignment_bytes, alignment, no_ra) orelse return null,
vtable.alloc(no_context, n + alignment_bytes, alignment, no_ra) orelse return nomem(),
);
const base = ptr + alignment_bytes;
const header: *Header = .fromBase(base);
@ -78,6 +78,11 @@ fn malloc(n: usize) callconv(.c) ?[*]align(alignment_bytes) u8 {
}
fn aligned_alloc(alloc_alignment: usize, n: usize) callconv(.c) ?[*]align(alignment_bytes) u8 {
return aligned_alloc_inner(alloc_alignment, n) orelse return nomem();
}
/// Avoids setting errno so it can be called by `posix_memalign`.
fn aligned_alloc_inner(alloc_alignment: usize, n: usize) ?[*]align(alignment_bytes) u8 {
const size = std.math.cast(Header.Size, n) orelse return null;
const max_align = alignment.max(.fromByteUnits(alloc_alignment));
const max_align_bytes = max_align.toByteUnits();
@ -94,7 +99,7 @@ fn aligned_alloc(alloc_alignment: usize, n: usize) callconv(.c) ?[*]align(alignm
}
fn calloc(elems: usize, len: usize) callconv(.c) ?[*]align(alignment_bytes) u8 {
const n = std.math.mul(usize, elems, len) catch return null;
const n = std.math.mul(usize, elems, len) catch return nomem();
const base = malloc(n) orelse return null;
@memset(base[0..n], 0);
return base;
@ -106,7 +111,7 @@ fn realloc(opt_old_base: ?[*]align(alignment_bytes) u8, n: usize) callconv(.c) ?
return null;
}
const old_base = opt_old_base orelse return malloc(n);
const new_size = std.math.cast(Header.Size, n) orelse return null;
const new_size = std.math.cast(Header.Size, n) orelse return nomem();
const old_header: *Header = .fromBase(old_base);
assert(old_header.padding == 0);
const old_size = old_header.size;
@ -122,7 +127,8 @@ fn realloc(opt_old_base: ?[*]align(alignment_bytes) u8, n: usize) callconv(.c) ?
no_ra,
)) |new_ptr| @alignCast(new_ptr + old_alignment_bytes) else b: {
const new_ptr: [*]align(alignment_bytes) u8 = @alignCast(
vtable.alloc(no_context, n + old_alignment_bytes, old_alignment, no_ra) orelse return null,
vtable.alloc(no_context, n + old_alignment_bytes, old_alignment, no_ra) orelse
return nomem(),
);
const new_base: [*]align(alignment_bytes) u8 = @alignCast(new_ptr + old_alignment_bytes);
const copy_len = @min(new_size, old_size);
@ -139,7 +145,7 @@ fn realloc(opt_old_base: ?[*]align(alignment_bytes) u8, n: usize) callconv(.c) ?
}
fn reallocarray(opt_base: ?[*]align(alignment_bytes) u8, elems: usize, len: usize) callconv(.c) ?[*]align(alignment_bytes) u8 {
const n = std.math.mul(usize, elems, len) catch return null;
const n = std.math.mul(usize, elems, len) catch return nomem();
return realloc(opt_base, n);
}
@ -173,10 +179,14 @@ fn memalign(alloc_alignment: usize, n: usize) callconv(.c) ?[*]align(alignment_b
fn posix_memalign(result: *?[*]align(alignment_bytes) u8, alloc_alignment: usize, n: usize) callconv(.c) c_int {
if (alloc_alignment < @sizeOf(*anyopaque)) return @intFromEnum(std.c.E.INVAL);
if (n == 0) {
result.* = null;
} else {
result.* = aligned_alloc(alloc_alignment, n) orelse return @intFromEnum(std.c.E.NOMEM);
}
result.* = aligned_alloc_inner(alloc_alignment, n) orelse return @intFromEnum(std.c.E.NOMEM);
return 0;
}
/// Libc memory allocation functions must set errno in addition to returning
/// `null`.
fn nomem() ?[*]align(alignment_bytes) u8 {
@branchHint(.cold);
std.c._errno().* = @intFromEnum(std.c.E.NOMEM);
return null;
}