From 4848c3a1ad2bfd956419351afb60928e290f2be1 Mon Sep 17 00:00:00 2001 From: Isaac Freund Date: Wed, 26 Mar 2025 14:12:25 +0100 Subject: [PATCH] std: fix sentinel handling in Allocator interface Currently the only function that handles sentinel terminated slices properly is free. All uses of mem.sliceAsBytes() in the allocator interface lack proper handling of a possible sentinel. This commit changes the Allocator interface to use @ptrCast() plus the new mem.absorbSentinel() instead. Reported-by: David Vanderson References: https://github.com/ziglang/zig/pull/19984 References: https://github.com/ziglang/zig/pull/23020 --- lib/std/mem/Allocator.zig | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/lib/std/mem/Allocator.zig b/lib/std/mem/Allocator.zig index caf049f296..00298ae71e 100644 --- a/lib/std/mem/Allocator.zig +++ b/lib/std/mem/Allocator.zig @@ -322,7 +322,7 @@ pub fn resize(self: Allocator, allocation: anytype, new_len: usize) bool { if (allocation.len == 0) { return false; } - const old_memory = mem.sliceAsBytes(allocation); + const old_memory: []u8 = @ptrCast(@constCast(mem.absorbSentinel(allocation))); // I would like to use saturating multiplication here, but LLVM cannot lower it // on WebAssembly: https://github.com/ziglang/zig/issues/9660 //const new_len_bytes = new_len *| @sizeOf(T); @@ -368,7 +368,7 @@ pub fn remap(self: Allocator, allocation: anytype, new_len: usize) ?@TypeOf(allo new_memory.len = new_len; return new_memory; } - const old_memory = mem.sliceAsBytes(allocation); + const old_memory: []u8 = @ptrCast(@constCast(mem.absorbSentinel(allocation))); // I would like to use saturating multiplication here, but LLVM cannot lower it // on WebAssembly: https://github.com/ziglang/zig/issues/9660 //const new_len_bytes = new_len *| @sizeOf(T); @@ -420,7 +420,7 @@ pub fn reallocAdvanced( return ptr; } - const old_byte_slice = mem.sliceAsBytes(old_mem); + const old_byte_slice: []u8 = @ptrCast(@constCast(mem.absorbSentinel(old_mem))); const byte_count = math.mul(usize, @sizeOf(T), new_n) catch return error.OutOfMemory; // Note: can't set shrunk memory to undefined as memory shouldn't be modified on realloc failure if (self.rawRemap(old_byte_slice, .fromByteUnits(slice_info.alignment orelse @alignOf(T)), byte_count, return_address)) |p| { @@ -443,8 +443,7 @@ pub fn reallocAdvanced( pub fn free(self: Allocator, memory: anytype) void { const slice_info = @typeInfo(@TypeOf(memory)).pointer; comptime assert(slice_info.size == .slice); - const mem_with_sent = memory[0 .. memory.len + @intFromBool(slice_info.sentinel() != null)]; - const bytes: []u8 = @ptrCast(@constCast(mem_with_sent)); + const bytes: []u8 = @ptrCast(@constCast(mem.absorbSentinel(memory))); if (bytes.len == 0) return; @memset(bytes, undefined); self.rawFree(bytes, .fromByteUnits(slice_info.alignment orelse @alignOf(slice_info.child)), @returnAddress());