X-Git-Url: http://git.tremily.us/?a=blobdiff_plain;f=configure.ac;h=41ac9a5e2d29b5f797a03052c3a17a8b42dac093;hb=d2216a4b133f90a543a0e4c4a9f9809a043012d6;hp=ad215cc4a10ed95804e7cec929f003c985d25a3d;hpb=6b34d6e692b751e7f62ea7bdce86a641c9b72468;p=git.git

diff --git a/configure.ac b/configure.ac
index ad215cc4a..41ac9a5e2 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'])