Commit 8f61a7d34a33c2ec912c3f4404d69586e721c75a | zig | Meg's Mirrors

author	rpkak <rpkak@noreply.codeberg.org> 2026-09-17 08:59:38+02:00
committer	Alex Rønne Petersen <alex@alexrp.com> 2026-09-17 15:35:12+02:00
log	8f61a7d34a33c2ec912c3f4404d69586e721c75a
tree	dee542054a456d4ad6d7d6afbc1c0ef01fcd68e9
parent	b0e7ebc24fdbd17f01180450c0e12f6187ef3f27

libzigc: strnlen, wcsnlen: don't read past first zero

Previously is was assumed, that all of str[0..max] is readable.

5 files changed, 29 insertions(+), 3 deletions(-)

lib
- c
  - string.zig
  - wchar.zig
- std
  - c.zig
test
- c
  - string.zig
  - wchar.zig

lib/c/string.zig+4-1

...	...	@@ -224,7 +224,10 @@ fn stpncpy(noalias dst: []c_char, noalias src: [:0]const c_char, max: usize) c
224	224	}
225	225
226	226	fn strnlen(str: [*:0]const c_char, max: usize) callconv(.c) usize {
227		return std.mem.findScalar(u8, @ptrCast(str[0..max]), 0) orelse max;
	227	for (0..max) \|i\| {
	228	if (str[i] == 0) return i;
	229	}
	230	return max;
228	231	}
229	232
230	233	fn memmem(haystack: const anyopaque, haystack_len: usize, needle: const anyopaque, needle_len: usize) callconv(.c) ?*anyopaque {

lib/c/wchar.zig+5-2

...	...	@@ -79,11 +79,14 @@ fn wmemset(dest: []wchar_t, elem: wchar_t, len: usize) callconv(.c) []wchar_t
79	79	}
80	80
81	81	fn wcslen(str: [*:0]const wchar_t) callconv(.c) usize {
82		return wcsnlen(str, std.math.maxInt(usize));
	82	return std.mem.len(str);
83	83	}
84	84
85	85	fn wcsnlen(str: [*:0]const wchar_t, max: usize) callconv(.c) usize {
86		return std.mem.findScalar(wchar_t, str[0..max], 0) orelse max;
	86	for (0..max) \|i\| {
	87	if (str[i] == 0) return i;
	88	}
	89	return max;
87	90	}
88	91
89	92	fn wcscmp(a: [:0]const wchar_t, b: [:0]const wchar_t) callconv(.c) c_int {

lib/std/c.zig+2

...	...	@@ -11471,7 +11471,9 @@ pub const strdup = switch (builtin.abi) {
11471	11471	.msvc => private._strdup,
11472	11472	else => private.strdup,
11473	11473	};
	11474	pub extern "c" fn strnlen(s: [*:0]const c_char, n: usize) callconv(.c) usize;
11474	11475	pub extern "c" fn strndup(s: [:0]const c_char, n: usize) ?[:0]c_char;
	11476	pub extern "c" fn wcsnlen(s: [*:0]const wchar_t, n: usize) callconv(.c) usize;
11475	11477	pub const wcsdup = switch (builtin.abi) {
11476	11478	.msvc => private._wcsdup,
11477	11479	else => private.wcsdup,

test/c/string.zig+9

...	...	@@ -50,3 +50,12 @@ test "strndup" {
50	50	const copy3_u8: [*:0]u8 = @ptrCast(copy3);
51	51	try testing.expectEqualStrings("Hello", std.mem.span(@as([*:0]const u8, copy3_u8)));
52	52	}
	53
	54	test "strnlen" {
	55	const str: [*:0]const u8 = "Hello";
	56	try testing.expectEqual(3, c.strnlen(@ptrCast(str), 3));
	57	try testing.expectEqual(4, c.strnlen(@ptrCast(str), 4));
	58	try testing.expectEqual(5, c.strnlen(@ptrCast(str), 5));
	59	try testing.expectEqual(5, c.strnlen(@ptrCast(str), 6));
	60	try testing.expectEqual(5, c.strnlen(@ptrCast(str), 7));
	61	}

test/c/wchar.zig+9

...	...	@@ -32,3 +32,12 @@ test "wcsdup empty string" {
32	32	defer c.free(cpy);
33	33	try testing.expectEqual(@as(c.wchar_t, 0), cpy[0]);
34	34	}
	35
	36	test "wcsnlen" {
	37	const wcs: [*:0]const c.wchar_t = &.{ 'H', 'e', 'l', 'l', 'o' };
	38	try testing.expectEqual(3, c.wcsnlen(wcs, 3));
	39	try testing.expectEqual(4, c.wcsnlen(wcs, 4));
	40	try testing.expectEqual(5, c.wcsnlen(wcs, 5));
	41	try testing.expectEqual(5, c.wcsnlen(wcs, 6));
	42	try testing.expectEqual(5, c.wcsnlen(wcs, 7));
	43	}