On Mon, Jun 25, 2007 at 03:15:39PM +0200, Takashi Iwai wrote: [...] > > #include <sys/select.h> > > #include <alsa/global.h> > > > > $ gcc -c --std=c99 x.c > > In file included from x.c:2: > > /usr/include/alsa/global.h:134: error: redefinition of 'struct timeval' > > /usr/include/alsa/global.h:139: error: redefinition of 'struct timespec' > > > > (Without #include <sys/select.h> only 'struct timespec' is redefined.) > > > > IMHO attempts to define structures which should be defined by system > > headers are too dangerous - if someone is using preprocessor flags > > which hide required parts of system headers, it is their problem, and > > the risk of mismatch is too high. > > I agree. > > Jaroslav, which system has no definition of these types? Maybe it'd > be better to check it in configure script, rather than the simple > ifdef. This won't help here - the above problem happens when alsa-lib headers are used by other programs, not when alsa-lib is built itself. > > BTW, <time.h> does not provide 'struct timeval' at all, even with > > _GNU_SOURCE - it defines only 'struct timespec'; however, this does > > not cause problems, because ALSA headers currently use only pointers > > to snd_timestamp_t, which works even without a complete definition of > > 'struct timeval'. We can try to include <sys/time.h> to get 'struct > > timeval', or even <sys/select.h> (which currently seems to provide > > both 'struct timeval' and 'struct timespec' even with -ansi, and > > http://www.opengroup.org/onlinepubs/009695399/basedefs/sys/select.h.html > > tells that it should always provide their definitions). > > A patch is welcome :) Just not sure which one... The situation on my system (with glibc-2.5) is as follows: - <time.h> defines 'struct timespec', unless -ansi (or -std=c99) option is used; it never defines 'struct timeval', even with -D_GNU_SOURCE (which should enable everything). This means that if only <time.h> is used, alsa/timer.h will not compile with -ansi due to the 'snd_htimestamp_t tstamp' member in snd_timer_tread_t, unless the program includes some other header which defines 'struct timespec' before alsa/timer.h. - <sys/time.h> defines both 'struct timeval' and 'struct timespec', even with -ansi; however, according to the current Open Group spec (http://www.opengroup.org/onlinepubs/009695399/basedefs/sys/time.h.html), <sys/time.h> must provide only 'struct timeval' and is not required to provide 'struct timespec', so the behavior may change in a future glibc release - again, a missing 'struct timespec' definition is fatal for alsa/timer.h. - <sys/select.h> defines both 'struct timeval' and 'struct timespec' even with -ansi. In the Open Group spec <sys/select.h> is specified to define 'struct timeval', and also define 'struct timespec' "as described in <time.h>" (where it is described as optional), so it should be not worse than <time.h>. Would it be OK to include <sys/select.h> instead of <time.h> and remove attempt to define system structs from alsa/global.h? Another option is to include both <time.h> and <sys/time.h>.
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