Re: [RFC PATCH 3/3] tools/nolibc: add a new "install_all_archs" target

["Arnd Bergmann" <arnd@arndb.de>]

On Fri, Jun 27, 2025, at 05:25, Willy Tarreau wrote:
> On Thu, Jun 26, 2025 at 11:15:07PM +0200, Arnd Bergmann wrote:
>> On Thu, Jun 26, 2025, at 22:18, Thomas Weißschuh wrote:

>> If it's indeed possible to concatenate the path name (I couldn't
>> figure that out either), that could also be done in place of the
>> symlink but simpler than the #if/#elif/#elif/... block, like
>> 
>> #include <arch.h> // defines ARCH_PREFIX
>> #include CONCAT(ARCH_PREFIX, ioctl.h)
>
> I have never found how it would be possible to do that, let alone in a
> more or less portable way, because #include doesn't take a C-string in
> argument but a special syntax which is specific to it ("x" or <x>). It
> doesn't support concatenating strings for example:
>
>   #include "stdio"".h"
>
>   $ gcc -E inc.h
>   inc.h:1:17: warning: extra tokens at end of #include directive
>       1 | #include "stdio"".h"
>         |                 ^~~~
>   inc.h:1:10: fatal error: stdio: No such file or directory
>       1 | #include "stdio"".h"
>         |          ^~~~~~~

This variant does seem to work with gcc and clang:

#define ARCH i386
#define __ARCH_HEADER(a, b) <a ## _ ## b>
#define _ARCH_HEADER(a, b) __ARCH_HEADER(a, b)
#include _ARCH_HEADER(ARCH, stdio.h)

Or even simpler

#define _NOLIBC_ARCH_HEADER(file) <i386_ ## file>

The ## concatenation is a bit limited here since cpp requires
both sides to expand to an identifier, meaning you can have
a '_' next to it, but not a '/' or '-'.

      Arnd