Subject: Re: Compiler warning under cygwin/mingw

From: Ramsay Jones <[email-masked]>
Date: Thu, 3 Mar 2016 03:33:19 +0000

On 29/02/16 12:32, Ramsay Jones wrote:
> 
> 
> On 29/02/16 10:40, Torsten Bögershausen wrote:
>> That compiles OK, thanks.
>>
>>
>> Sorry for high-jacking this thread, but while compiling under CYGWIN,
>> found one warning:
>>
>>    LINK git-credential-store.exe
>>     CC daemon.o
>> daemon.c: In function ‘drop_privileges’:
>> daemon.c:1136:15: warning: implicit declaration of function ‘initgroups’ [-Wimplicit-function-declaration]
>>   if (cred && (initgroups(cred->pass->pw_name, cred->gid) ||
> 
> Yeah, this has been there for a while - except it depends on which version
> of the header files you have. (Some may not see the warning).
> 
> I have 'fixed' this twice before, then updated my installation and
> a change to the system headers broke it again! (The headers are
> currently 'broken'). So, I got tired of fixing it up and have left
> it a while - you never know a new update may fix it! ;-)
> 
> [I personally don't use the git daemon on cygwin, so I don't know
> if this a problem in practice.]

BTW, I forgot to mention that I have had a patch in my local repo for
ages which addresses this issue. However, although this patch fixes
the problem for me, with the header files I currently have installed, it
would just as easily _introduce_ this warning for those that don't
currently see it! ;-)

I suppose that I could send a patch which sets NO_INITGROUPS in the
Makefile, until the system header files are fixed. What do you think?

The correct solution is to fix the <grp.h> header file. I have been
a bit reluctant to tackle that, because I'm not familiar with the
cygwin project development process. Since Newlib is an upstream
project to cygwin, should I go there first/instead?

Anyway, I had a quick squint at the header and I think it needs to
be changed something like the diff below. (I've also attached the
new grp.h file).

[Note: I didn't know what to do about _PATH_GROUP, setgrfile(),
group_from_gid() and setgroupent(), so I punted on those!]

Now, If only we knew someone who could try introducing such a fix
to the cygwin project ...

ATB,
Ramsay Jones
-- >8 --
diff --git a/usr/include/grp.h b/grp.h
index c3a5a67..f2f1902 100644
--- a/usr/include/grp.h
+++ b/grp.h
@@ -67,25 +67,27 @@ extern "C" {
 #ifndef __INSIDE_CYGWIN__
 struct group	*getgrgid (gid_t);
 struct group	*getgrnam (const char *);
+#if defined __POSIX_VISIBLE || defined __BSD_VISIBLE
 int		 getgrnam_r (const char *, struct group *,
 			char *, size_t, struct group **);
 int		 getgrgid_r (gid_t, struct group *,
 			char *, size_t, struct group **);
-#ifndef _POSIX_SOURCE
-struct group	*getgrent (void);
+#endif
+#if defined __BSD_VISIBLE || defined _XOPEN_SOURCE_EXTENDED
 void		 setgrent (void);
+#if __XSI_VISIBLE >= 700
+struct group	*getgrent (void);
 void		 endgrent (void);
+#endif
+#endif
+#if defined __BSD_VISIBLE
+int		 initgroups (const char *, gid_t);
+#endif
 #ifndef __CYGWIN__
-void		 setgrfile (const char *);
-#endif /* !__CYGWIN__ */
-#ifndef _XOPEN_SOURCE
-#ifndef __CYGWIN__
+void		 setgrfile (const char *); /* 4.3BSD-Reno & Minix */
 char		*group_from_gid (gid_t, int);
-int		 setgroupent (int);
+int		 setgroupent (int); /* 4.3BSD-Reno & Mac OS X */
 #endif /* !__CYGWIN__ */
-int		 initgroups (const char *, gid_t);
-#endif /* !_XOPEN_SOURCE */
-#endif /* !_POSIX_SOURCE */
 #endif /* !__INSIDE_CYGWIN__ */
 
 #ifdef __cplusplus