Windows heap_allocator doesn't resize properly

[cmpowys]

Context

Odin: dev-2025-02-nightly:748a771
OS: Windows 11 Professional (version: 24H2), build 26100.3194
CPU: 13th Gen Intel(R) Core(TM) i5-1335U
RAM: 16107 MiB
Backend: LLVM 18.1.8

Expected Behavior

Calling the heap_allocator proc with .Resize doesn't copy over old data.

Current Behavior

Old data is not copied over after .Resize call.

Failure Information (for bugs)

Steps to Reproduce

The following code reproduces the issue for me. I am assuming test^ == 5 after the realloc call.

context.allocator = runtime.heap_allocator();
bytes, allocator_error := runtime.heap_allocator_proc(context.allocator.data, .Alloc, 64, align_of(rawptr), nil, 0);
assert(allocator_error == runtime.Allocator_Error.None && bytes != nil);
test := cast(^u64)raw_data(bytes);
test^ = 5;
test2 := test;
assert(test^ == 5);
bytes, allocator_error = runtime.heap_allocator_proc(context.allocator.data, .Resize, auto_cast 256, align_of(rawptr)*2, raw_data(bytes), 0);
assert(allocator_error == runtime.Allocator_Error.None && bytes != nil);
test = cast(^u64)raw_data(bytes);
assert(test2 != test);
assert(test^ == 5); // code fails here

Failure Logs

.... main.odin(193:2) runtime assertion: test^ == 5

[cmpowys]

I am not sure if the following is correct in https://github.com/odin-lang/Odin/blob/master/base/runtime/heap_allocator.odin
I would think if force_copy = true, we resize instead of alloc.

force_copy := old_ptr != nil && alignment > align_of(rawptr)

if old_ptr != nil && !force_copy {
original_old_ptr := ([^]rawptr)(old_ptr)[-1]
allocated_mem = heap_resize(original_old_ptr, space)
} else {
allocated_mem = heap_alloc(space, zero_memory)
}

[blob1807]

When you're resizing you're telling it the old size is 0 not 64. So it thinks there's nothing to copy over.