issue-592: handle recent mingw with C++11 threads

Somehow it's c++ headers (like string) define pthread symbols without
even us asking for. That breaks old assumption that pthread symbols
are not available on windows.

In order to fix that we detect this condition in configure.ac and
avoid defining windows versions of pthread symbols.

4 files changed, 35 insertions, 11 deletions

diff --git a/Makefile.am b/Makefile.am
index b0a9dfb..caa19a7 100755
--- a/Makefile.am
+++ b/Makefile.am
@@ -264,7 +264,11 @@ libsysinfo_la_LIBADD += -lshlwapi
 # patch_functions.cc #includes tcmalloc.cc, so no need to link it in.
 TCMALLOC_CC =
 # windows has its own system for threads and system memory allocation.
+if HAVE_PTHREAD_DESPITE_ASKING_FOR
+MAYBE_THREADS_CC = src/maybe_threads.cc
+else
 MAYBE_THREADS_CC =
+endif
 SYSTEM_ALLOC_CC =
 else !MINGW
 # spinlock is the only code that uses atomicops.
diff --git a/configure.ac b/configure.ac
index 1fb8abd..f76c060 100644
--- a/configure.ac
+++ b/configure.ac
@@ -348,6 +348,26 @@ AC_CHECK_DECLS(uname,,, [#include <sys/utsname.h>])
 # In fact, a lot of the code in this directory depends on pthreads
 ACX_PTHREAD
 
+AC_LANG_SAVE
+AC_LANG_CPLUSPLUS
+AC_MSG_CHECKING([whether pthread symbols are available in C++ without including pthread.h])
+acx_pthread_despite_asking_for=no
+AC_LINK_IFELSE(
+  [AC_LANG_PROGRAM([
+      #include <string>
+      #include <vector>
+  ],[
+      pthread_t th; pthread_join(th, 0);
+  ])],[
+    acx_pthread_despite_asking_for=yes
+    AC_DEFINE(HAVE_PTHREAD_DESPITE_ASKING_FOR, 1, [defined to 1 if pthread symbols are exposed even without include pthread.h])
+    AC_DEFINE(HAVE_PTHREAD, 1, [])
+  ])
+AC_MSG_RESULT([$acx_pthread_despite_asking_for])
+AC_LANG_RESTORE
+
+AM_CONDITIONAL(HAVE_PTHREAD_DESPITE_ASKING_FOR, test x"$acx_pthread_despite_asking_for" == xyes)
+
 # Find out what namespace 'normal' STL code lives in
 AC_CXX_STL_NAMESPACE
 
diff --git a/src/windows/mingw.h b/src/windows/mingw.h
index 5acefeb..0586e62 100644
--- a/src/windows/mingw.h
+++ b/src/windows/mingw.h
@@ -59,7 +59,9 @@
 // Some mingw distributions have a pthreads wrapper, but it doesn't
 // work as well as native windows spinlocks (at least for us).  So
 // pretend the pthreads wrapper doesn't exist, even when it does.
+#ifndef HAVE_PTHREAD_DESPITE_ASKING_FOR
 #undef HAVE_PTHREAD
+#endif
 
 #define HAVE_PID_T
 
diff --git a/src/windows/port.h b/src/windows/port.h
index 0a9b0d8..c66a296 100644
--- a/src/windows/port.h
+++ b/src/windows/port.h
@@ -133,7 +133,14 @@ inline bool pthread_equal(pthread_t left, pthread_t right) {
   return left == right;
 }
 
+/*
+ * windows/port.h defines compatibility APIs for several .h files, which
+ * we therefore shouldn't be #including directly.  This hack keeps us from
+ * doing so.  TODO(csilvers): do something more principled.
+ */
+#define GOOGLE_MAYBE_THREADS_H_ 1
 /* This replaces maybe_threads.{h,cc} */
+
 EXTERN_C pthread_key_t PthreadKeyCreate(void (*destr_fn)(void*));  /* port.cc */
 
 inline int perftools_pthread_key_create(pthread_key_t *pkey,
@@ -165,12 +172,13 @@ EXTERN_C int perftools_pthread_once(pthread_once_t *once_control,
                                     void (*init_routine)(void));
 
 #endif  /* __cplusplus */
-#endif  /* HAVE_PTHREAD */
 
 inline void sched_yield(void) {
   Sleep(0);
 }
 
+#endif  /* HAVE_PTHREAD */
+
 /*
  * __declspec(thread) isn't usable in a dll opened via LoadLibrary().
  * But it doesn't work to LoadLibrary() us anyway, because of all the
@@ -474,16 +482,6 @@ inline long long atoll(const char *nptr) {
 /* tcmalloc.cc calls this so we can patch VirtualAlloc() et al. */
 extern void PatchWindowsFunctions();
 
-// ----------------------------------- BUILD-SPECIFIC
-
-/*
- * windows/port.h defines compatibility APIs for several .h files, which
- * we therefore shouldn't be #including directly.  This hack keeps us from
- * doing so.  TODO(csilvers): do something more principled.
- */
-#define GOOGLE_MAYBE_THREADS_H_ 1
-
-
 #endif  /* _WIN32 */
 
 #undef inline