Max Horn <max@xxxxxxxxx> writes: > The configure script checks whether certain flags are required to use > pthreads. But it did not consider that *none* might be needed (as is the > case on Mac OS X). This lead to configure adding "-mt" to the list of > flags (which does nothing on OS X except producing a warning). This in > turn triggered a compiler warning on every single file. > > To solve this, we now first check if pthreads work without extra flags. > This means the check is now order dependant, hence a comment is added > explaining this, and the reasons for it. > > Note that it might be possible to write an order independent test, but > it does not seem worth the extra effort required for implementing and > testing such a solution, when this simple solution exists and works. > > Signed-off-by: Max Horn <max@xxxxxxxxx> > --- > > This is actually a revised version from my patch > "Change configure to check if pthreads are usable without any extra flags" > from July. I simply had forgotten all about it :-(. Will queue, but we would need wider testing to avoid "compiles well without an option but fails to link" issues similar to cea13a8 (Improve test for pthreads flag, 2011-03-28) on other people's platforms (I know you tested on Mac OS X and over there it compiles and links well---I am worried about others). Thanks. > Chers, > Max > > configure.ac | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) > > diff --git a/configure.ac b/configure.ac > index ad215cc..41ac9a5 100644 > --- a/configure.ac > +++ b/configure.ac > @@ -1021,7 +1021,17 @@ if test -n "$USER_NOPTHREAD"; then > # -D_REENTRANT' or some such. > elif test -z "$PTHREAD_CFLAGS"; then > threads_found=no > - for opt in -mt -pthread -lpthread; do > + # Attempt to compile and link some code using pthreads to determine > + # required linker flags. The order is somewhat important here: We > + # first try it without any extra flags, to catch systems where > + # pthreads are part of the C library, then go on testing various other > + # flags. We do so to avoid false positives. For example, on Mac OS X > + # pthreads are part of the C library; moreover, the compiler allows us > + # to add "-mt" to the CFLAGS (although it will do nothing except > + # trigger a warning about an unused flag). Hence if we checked for > + # "-mt" before "" we would end up picking it. But unfortunately this > + # would then trigger compiler warnings on every single file we compile. > + for opt in "" -mt -pthread -lpthread; do > old_CFLAGS="$CFLAGS" > CFLAGS="$opt $CFLAGS" > AC_MSG_CHECKING([for POSIX Threads with '$opt']) -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html