cygwin 3.6.0 vs. libbsd 0.11.7-3: -lbsd breaks setproctitle()

Wed Feb 19 13:25:33 GMT 2025

Hi Corinna,
Corinna Vinschen via Cygwin wrote:
> Hi Christian,
>> On Feb 19 11:14, Christian Franke via Cygwin wrote:
>> Testcase:
>>>> $ uname -r
>> 3.6.0-0.375.ged18acfe8c76.x86_64
>>>> $ cygcheck -f /usr/include/bsd/unistd.h
>> libbsd-devel-0.11.7-3
>>>> $ cat spt.c
>> #include <unistd.h>
>>>> int main(int argc, char **argv, char **envp)
>> {
>>   initsetproctitle(argc, argv, envp);
>>   setproctitle("argc = %d", argc);
>>   sleep(2);
>>   return 0;
>> }
>>>> $ gcc -o spt-bsdovl -isystem /usr/include/bsd -DLIBBSD_OVERLAY spt.c -l bsd
>>>> $ gcc -o spt-bsd spt.c -l bsd
>>>> $ gcc -o spt-nobsd spt.c
>>>> $ ./spt-bsdovl
>> spt-bsdovl: setproctitle not initialized, please either call
>> setproctitle_init() or link against libbsd-ctor.
>>>> $ ./spt-bsd
>> spt-bsd: setproctitle not initialized, please either call
>> setproctitle_init() or link against libbsd-ctor.
>>>> $ ./spt-nobsd & procps -o pid,args -p $!
>> [1] 2750
>>   PID COMMAND
>>  2750 spt-nobsd: argc = 1
> The problem the Cygwin patch was supposed to fix is that the libbsd
> version of setproctitle just doesn't work correctly on Cygwin:
>> $ uname -r
> 3.5.7-1.x86_64
> $ ./spt-bsdovl & procps -o pid,args -p $!
> [1] 140
> PID COMMAND
> 140 spt-bsdovl:
>> The way the include file /usr/include/bsd/unistd.h is designed,
> we could make sure the libbsd version is used, by tweaking
> /usr/include/sys/unistd.h:
>> diff --git a/newlib/libc/include/sys/unistd.h b/newlib/libc/include/sys/unistd.h
> index e62e38d10ccf..732356d6a14e 100644
> --- a/newlib/libc/include/sys/unistd.h
> +++ b/newlib/libc/include/sys/unistd.h
> @@ -212,7 +212,7 @@ int setpgid (pid_t __pid, pid_t __pgid);
> #if __SVID_VISIBLE || __XSI_VISIBLE >= 500
> int setpgrp (void);
> #endif
> -#if defined(__CYGWIN__) && __BSD_VISIBLE
> +#if defined(__CYGWIN__) && __BSD_VISIBLE && !defined(LIBBSD_OVERLAY)
> /* Stub for Linux libbsd compatibility. */
> #define initsetproctitle(c, a, e) setproctitle_init((c), (a), (e))
> static inline void setproctitle_init (int, char *[], char *[]) {}
>> But that still allows to link against a non-working setproctitle.

Yes, and it won't work if bsd/unistd.h is included without 
LIBBSD_OVERLAY which is discouraged but still documented on libbsd(7).
> So I think we rather shouldn't supply the libbsd version of
> setproctitle_init/setproctitle anymore, as soon as cygwin 3.6.0 is
> released.
>> What do you think?

Makes sense. But then existing programs already using the functions from 
cygbsd-0.dll would no longer start. Perhaps keep the symbols in the DLL 
only for some time?
-- 
Regards,
Christian