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Date: Wed, 5 Mar 2025 15:51:02 -0500
To: "cygwin AT cygwin DOT com" <cygwin AT cygwin DOT com>
Subject: Re: Cygwin 3.6: clang cannot use /usr/include/unistd.h, issue with
 |setproctitle_init()| ...
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From: Glenn Strauss via Cygwin <cygwin AT cygwin DOT com>
Reply-To: Glenn Strauss <gs-cygwin DOT com AT gluelogic DOT com>
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On Wed, Mar 05, 2025 at 08:27:53PM +0000, Lavrentiev, Anton (NIH/NLM/NCBI) [C] via Cygwin wrote:
> >  We could change this to a macro instead:
> >
> > -static inline void setproctitle_init (int, char *[], char *[]) {}
> > +#define setproctitle_init(c, a, e)
> 
> Changing to the empty marco removes the side effects in the arguments (such as len++, for example),
> which may silently break existing code -- so I think it's not a good idea.  If the idea to use the empty
> arguments was not to implicitly document them (because the API was slated for removal, IIRC), then
> naming them just with "arg1", "arg2" (rather than leaving empty altogether) should help better, IMO.
> 
> Anton Lavrentiev
> Contractor NIH/NLM/NCBI

If you want the side effects of the arguments and still want a macro:

  #define setproctitle_init(c, a, e) \
    do { (void)(c); (void)(a); (void)(e); } while (0)

or, since it is unlikely (though possible) that someone has defined a
single-letter macro for 'c', 'a', or 'b':

static inline void setproctitle_init (int c, char *a[], char *b[])
{
    (void)(c);
    (void)(a);
    (void)(e);
}

or use the intended, more descriptive names in the prototype

static inline void setproctitle_init (int argc, char *argv[], char *envp[])
{
    (void)(argc);
    (void)(argv);
    (void)(envp);
}

If gcc or clang, you could also add __attribute__((__unused__)),
though it should probaby be its own macro so that it could be no-op for
certain compilers:

There is also [[maybe_unused]]
https://clang.llvm.org/docs/AttributeReference.html#maybe-unused-unused
https://learn.microsoft.com/en-us/cpp/error-messages/compiler-warnings/compiler-warning-level-4-c4189?view=msvc-170

#ifndef __attribute_unused__
#ifdef _MSC_VER
#define __attribute_unused__ [[maybe_unused]]
#else
#define __attribute_unused__ __attribute__((__unused__)),
#endif
#endif

static inline void setproctitle_init (int argc     __attribute_unused__,
                                      char *argv[] __attribute_unused__,
                                      char *envp[] __attribute_unused__)
{
    (void)(argc);
    (void)(argv);
    (void)(envp);
}

Cheers, Glenn

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