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-rw-r--r--configure.ac12
1 files changed, 11 insertions, 1 deletions
diff --git a/configure.ac b/configure.ac
index c85888c851..55aae5f389 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 $CFLAGS"
AC_MSG_CHECKING([Checking for POSIX Threads with '$opt'])