cc-wrapper: set gl_cv_clean_version_stddef=yes on cygwin

[corngood]

This fixes errors such as:

error: unknown type name ‘wint_t’

Things done

• Built on platform:
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• Tested, as applicable:
  • NixOS tests in nixos/tests.
  • Package tests at passthru.tests.
  • Tests in lib/tests or pkgs/test for functions and "core" functionality.
• Ran nixpkgs-review on this PR. See nixpkgs-review usage.
• Tested basic functionality of all binary files, usually in ./result/bin/.
• Nixpkgs Release Notes
  • Package update: when the change is major or breaking.
• NixOS Release Notes
  • Module addition: when adding a new NixOS module.
  • Module update: when the change is significant.
• Fits CONTRIBUTING.md, pkgs/README.md, maintainers/README.md and other READMEs.

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[Ericson2314]

This feels to me like the wrong place to put this? At at least it exposes the absurdity of our GNU-autools-specific stdenv is.

[corngood]

Yeah, it's a hack. I can try to figure out where a real fix would go.

[Ericson2314]

Perhaps in mkDerivation itself.

[corngood]

For reference, here is the failure in gnugrep configure:

configure:21635: checking for clean definition of __STDC_VERSION_STDDEF_H__
configure:21652: x86_64-pc-cygwin-gcc -std=gnu23 -E  conftest.c
conftest.c:148:20: warning: undefining "__STDC_VERSION_STDDEF_H__"
  148 |             #undef __STDC_VERSION_STDDEF_H__
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~
conftest.c:151:15: error: #error "<time.h> defines __STDC_VERSION_STDDEF_H__"
  151 |             # error "<time.h> defines __STDC_VERSION_STDDEF_H__"
      |               ^~~~~
configure:21652: $? = 1
configure: failed program was:
| /* confdefs.h */
[...]
| /* end confdefs.h.  */
| /* https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114870 */
|             #include <stddef.h>
|             #undef __STDC_VERSION_STDDEF_H__
|             #include <time.h>
|             #ifdef __STDC_VERSION_STDDEF_H__
|             # error "<time.h> defines __STDC_VERSION_STDDEF_H__"
|             #endif
|
configure:21662: result: no

Edit: actually this happens on linux as well. I guess the stddef wrapper just doesn't work on cygwin. Investigating that now.

[corngood]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114870

In file included from /nix/store/06rxvqbpl4hzc5fnpjz8507raldygnbh-x86_64-pc-cygwin-gcc-14.3.0/x86_64-pc-cygwin/sys-include/sys/reent.h:16,
                 from /nix/store/06rxvqbpl4hzc5fnpjz8507raldygnbh-x86_64-pc-cygwin-gcc-14.3.0/x86_64-pc-cygwin/sys-include/stdio.h:60,
                 from ./stdio.h:55,
                 from argmatch.h:32,
                 from argmatch.c:25:
/nix/store/06rxvqbpl4hzc5fnpjz8507raldygnbh-x86_64-pc-cygwin-gcc-14.3.0/x86_64-pc-cygwin/sys-include/sys/_types.h:167:5: error: unknown type name ‘wint_t’
  167 |     wint_t __wch;
      |     ^~~~~~

I guess what happens is that the gnulib stddef.h wrapper disables __need_wint_t This happens on linux as well, so that if you add this to the end of a file:

#define __need_wint_t
#include <stddef.h>
wint_t foo;

The definition can't be found. The compile error above is because on cygwin sys/_types.h does something like this.

So I guess the <time.h> test was not a great way of detecting the original bug. It's actually been removed in latest gnulib in preparation for GCC 15, however it's been replaced with a check for GCC 13 or 14, so it wouldn't help here.

[corngood]

I made a PR to fix this in gnugrep: #469010

It may also be required in other projects, but I was able to rebuild nix without fixing anything else. Since it's dependent on the gnulib version, and likely to go away with GCC 15, I suppose we don't really need a global fix.

[corngood]

Since GCC 15 this problem now affects a lot of core gnu projects (iconv, gnupatch, gnugrep, etc).

It's fixed upstream in https://gitweb.git.savannah.gnu.org/gitweb/?p=gnulib.git;a=commitdiff;h=e529f4fbd08fa9e60c7092ba0f8cc976a735077c

Once that change rolls out, gl_cv_clean_version_stddef will no longer be used.

This feels to me like the wrong place to put this? At at least it exposes the absurdity of our GNU-autools-specific stdenv is.

I thought about this. It's really a libc problem with newlib-cygwin, but cc-wrapper is the place where libc is abstracted in terms of setup hooks.

[corngood]

@Ericson2314 This is one of the last things required for #475998. Any thoughts on my last comment?

[Ericson2314]

This a hack, but it is also a temporary one. So I can live it with. Cygwin must ship! (And other platforms are not affected.