[ruby-core:120997] [Ruby master Bug#21024] Ruby including <cstdbool> generates compilation warning with GCC 15, header is deprecated in C++17,

Issue #21024 has been updated by k0kubun (Takashi Kokubun).

Backport changed from 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: REQUIRED to 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: DONE

ruby_3_4 commit:b5c921e01074891680b45353519a1e0bfe7c1036.

----------------------------------------
Bug #21024: Ruby including <cstdbool> generates compilation warning with GCC 15, header is deprecated in C++17, 
https://bugs.ruby-lang.org/issues/21024#change-111905

* Author: jprokop (Jarek Prokop)
* Status: Closed
* ruby -v: ruby 3.4.1 (2024-12-25 revision 48d4efcb85) +PRISM [x86_64-linux]
* Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: DONE
----------------------------------------
C++ compiler in GCC 15 now generates a warning when trying to include `<cstdbool>`.
This file is being included when compiling with C++ compiler from `include/ruby/internal/stdbool.h`.

In C++, true, false and bool are keywords so including headers for boolean definitions should not be necessary.
Alternatively, just including <stdbool.h> should be sufficient as that is what the `#include <cstdbool>` results in with GCC.

Simplest fix is just deleting the lines that are including the file (see attached patch and comments 2 and 3 from downstream issue linked in the bottom section "Additional info").

Considering the wide array of compilers Ruby aims to support to be compiled with I wanted to make an issue here first to make sure
there isn't a supported compiler that wouldn't agree with this approach.

Reproduction:
Obtain GCC 15, for Fedora Rawhide there is currently a repo of maintainer, I use it in Fedora Rawhide container (podman is replaceable for docker here):
```
host$ podman run -it --rm registry.fedoraproject.org/fedora:rawhide bash
container# echo "[gcc_15]
name=pre-release GCC 15 Repo
baseurl=https://fedorapeople.org/~dmalcolm/gcc/gcc-15-mass-prebuild/$basearch
type=rpm-md
skip_if_unavailable=True
gpgcheck=0
repo_gpgcheck=0
enabled=1
enabled_metadata=1" > /etc/yum.repos.d/gcc_15.repo
container# dnf install --assumeyes g++ ruby-devel
```
^ should install `g++-15.0.0` and `ruby.h` needed for the reproducer.
Note: that baseurl is a custom space of a Fedora maintainer.

Have a file named for example `main.cpp`:
``` cpp
#include <ruby.h>

int main(void) {
	return 0;
}
```
Compile with GCC 15
```
$ g++ main.cpp
```

Current behavior:
Compiling throws warning:
```
$ g++ main.cpp
In file included from /usr/include/ruby/internal/stdbool.h:30,
                 from /usr/include/ruby/backward/2/bool.h:22,
                 from /usr/include/ruby/defines.h:74,
                 from /usr/include/ruby/ruby.h:25,
                 from /usr/include/ruby.h:38,
                 from reproducer.cpp:1:
/usr/include/c++/15/cstdbool:48:6: warning: #warning "<cstdbool> is deprecated in C++17, remove the #include" [-Wcpp]
   48 | #    warning "<cstdbool> is deprecated in C++17, remove the #include"
      |      ^~~~~~~
```

Expected:
Compilation throws no warnings and compiles the executable:
```
$ g++ reproducer.cpp
$ echo $?
0
```

Additional info:
```
$ g++ --version
g++ (GCC) 15.0.0 20241203 (Red Hat 15.0.0-0)
Copyright (C) 2024 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

```

This was met during recompilation of libdnf5 that includes `-Werror` in their compilation flags,
See downstream discussion: https://bugzilla.redhat.com/show_bug.cgi?id=2336567

Considering the inclusion of the <cstdbool> throws me up to 5 years ago back ( https://github.com/ruby/ruby/blob/9e6e39c3512f7a962c44dc3729c98a0f8be90341/include/ruby/3/stdbool.h ), I assume this warning will be the case with older rubies as well as newest master when using GCC 15.

---Files--------------------------------
0001-Stop-including-cstdbool-in-include-ruby-internal-std.patch (869 Bytes)


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