# -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 $CFLAGS"
- AC_MSG_CHECKING([Checking for POSIX Threads with '$opt'])
+ AC_MSG_CHECKING([for POSIX Threads with '$opt'])
AC_LINK_IFELSE([PTHREADTEST_SRC],
[AC_MSG_RESULT([yes])
NO_PTHREADS=