POC: use stdbool

[vrabaud]

This breaks the ABI

[wantehchang]

For backward compatibility, we can't make this change because int and bool have different sizes. Here is an experiment with Clang on Linux:

$ cat bool.c
#include <stdbool.h>
#include <stdio.h>

int main(void) {
  printf("sizeof(int) = %zu\n", sizeof(int));
  printf("sizeof(bool) = %zu\n", sizeof(bool));
  return 0;
}
$ clang --version
Debian clang version 19.1.7 (1)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/lib/llvm-19/bin
$ clang -Weverything bool.c
$ ./a.out
sizeof(int) = 4
sizeof(bool) = 1

[vrabaud]

Indeed, there is an ABI breakage, that was more a POC. Do we wait for 1.3.0 or we will never allow that?

[wantehchang]

v1.3.0 is a minor release, which allows new features but does not allow backward incompatible changes. v2.0.0 is a major release, which allows any changes.

We can either abandon this pull request and make this a conditionally-compiled change that we enable in a CI workflow.

[vrabaud]

This PR is now part of the CI in #2712