LocalFree and GlobalFree functions return an error if the free succeeds, while returning a success if the free fails

[Rileran]

Summary

Functions LocalFree and GlobalFree return Err when the free is successful, and Ok when the free fails.

The expected outcome would be the opposite.

Looking at the documentation for LocalFree tells us that if the function succeeds, the return value is NULL (or invalid).

Looking at the generated source code (for crate version 0.52.0), the function returns Ok when the return value is NOT NULL (or valid).

pub unsafe fn LocalFree<P0>(hmem: P0) -> ::windows_core::Result<HLOCAL>
where
    P0: ::windows_core::IntoParam<HLOCAL>,
{
    ::windows_targets::link!("kernel32.dll" "system" fn LocalFree(hmem : HLOCAL) -> HLOCAL);
    let result__ = LocalFree(hmem.into_param().abi());
    (!result__.is_invalid()).then(|| result__).ok_or_else(::windows_core::Error::from_win32)
}

Crate manifest

[package]
name = "windows-playground"
version = "0.1.0"
edition = "2021"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
windows = { version = "0.52.0", features = ["Win32_Foundation", "Win32_System_Memory"] }

Crate code

use windows::Win32::Foundation::LocalFree;
use windows::Win32::System::Memory::{LocalAlloc, LMEM_FIXED, LMEM_ZEROINIT};

fn main() {
    unsafe {
        let data = LocalAlloc(LMEM_FIXED | LMEM_ZEROINIT, 10).unwrap();
        // the next call fails if free is successfull
        // Error { code: HRESULT(0x00000000), message: "The operation completed successfully." }
        LocalFree(data).unwrap();
    }
}

[Rileran]

Just saw this is already on issue on the win32metadata repository microsoft/win32metadata#1557, closing this one.