Add pthread_atfork(3) feature test.

Some versions of Android provide a pthreads library without providing
pthread_atfork(), so in practice a separate feature test is necessary
for the latter.

configure.ac

@@ -1299,6 +1299,14 @@ if test "x$abi" != "xpecoff" ; then
   AC_CHECK_LIB([pthread], [pthread_create], [LIBS="$LIBS -lpthread"],
                [AC_SEARCH_LIBS([pthread_create], , ,
                                AC_MSG_ERROR([libpthread is missing]))])
+  JE_COMPILABLE([pthread_atfork(3)], [
+#include <pthread.h>
+], [
+  pthread_atfork((void *)0, (void *)0, (void *)0);
+], [je_cv_pthread_atfork])
+  if test "x${je_cv_pthread_atfork}" = "xyes" ; then
+    AC_DEFINE([JEMALLOC_HAVE_PTHREAD_ATFORK], [ ])
+  fi
 fi
 
 CPPFLAGS="$CPPFLAGS -D_REENTRANT"

include/jemalloc/internal/jemalloc_internal_defs.h.in

@@ -79,6 +79,9 @@
  */
 #undef JEMALLOC_HAVE_ISSETUGID
 
+/* Defined if pthread_atfork(3) is available. */
+#undef JEMALLOC_HAVE_PTHREAD_ATFORK
+
 /*
  * Defined if clock_gettime(CLOCK_MONOTONIC_COARSE, ...) is available.
  */

src/jemalloc.c

@@ -1264,8 +1264,9 @@ malloc_init_hard_recursible(void)
 
 	ncpus = malloc_ncpus();
 
-#if (!defined(JEMALLOC_MUTEX_INIT_CB) && !defined(JEMALLOC_ZONE) \
-    && !defined(_WIN32) && !defined(__native_client__))
+#if (defined(JEMALLOC_HAVE_PTHREAD_ATFORK) && !defined(JEMALLOC_MUTEX_INIT_CB) \
+    && !defined(JEMALLOC_ZONE) && !defined(_WIN32) && \
+    !defined(__native_client__))
 	/* LinuxThreads' pthread_atfork() allocates. */
 	if (pthread_atfork(jemalloc_prefork, jemalloc_postfork_parent,
 	    jemalloc_postfork_child) != 0) {