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compiler_rt: fix memcmp wrong for some inputs

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See the new test case - this fails in the previous implementation.

See #13303
This commit is contained in:
Andrew Kelley 2022-10-27 13:37:46 -07:00
parent 2991e4a454
commit 1f4f8d34a1
1 changed files with 13 additions and 14 deletions
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27
lib/compiler_rt/memcmp.zig
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@ -5,27 +5,26 @@ comptime {
@export(memcmp, .{ .name = "memcmp", .linkage = common.linkage });
}
pub fn memcmp(vl: ?[*]const u8, vr: ?[*]const u8, n: usize) callconv(.C) c_int {
@setRuntimeSafety(false);
var index: usize = 0;
while (index != n) : (index += 1) {
const compare_val = @bitCast(i8, vl.?[index] -% vr.?[index]);
if (compare_val != 0) {
return compare_val;
}
pub fn memcmp(vl: [*]const u8, vr: [*]const u8, n: usize) callconv(.C) c_int {
var i: usize = 0;
while (i < n) : (i += 1) {
const compared = @as(c_int, vl[i]) -% @as(c_int, vr[i]);
if (compared != 0) return compared;
}
return 0;
}
test "memcmp" {
const base_arr = &[_]u8{ 1, 1, 1 };
const arr0 = &[_]u8{ 1, 1, 1 };
const arr1 = &[_]u8{ 1, 1, 1 };
const arr2 = &[_]u8{ 1, 0, 1 };
const arr3 = &[_]u8{ 1, 2, 1 };
const arr4 = &[_]u8{ 1, 0xff, 1 };
try std.testing.expect(memcmp(base_arr[0..], arr1[0..], base_arr.len) == 0);
try std.testing.expect(memcmp(base_arr[0..], arr2[0..], base_arr.len) > 0);
try std.testing.expect(memcmp(base_arr[0..], arr3[0..], base_arr.len) < 0);
try std.testing.expect(memcmp(arr0, arr1, 3) == 0);
try std.testing.expect(memcmp(arr0, arr2, 3) > 0);
try std.testing.expect(memcmp(arr0, arr3, 3) < 0);
try std.testing.expect(memcmp(arr0, arr4, 3) < 0);
try std.testing.expect(memcmp(arr4, arr0, 3) > 0);
}