On Linux, call prctl to disable core dumps

Whenever I forget to turn off corekeeper, the regression tests
take ages to record all test-segfault's crashes.

Bug: https://bugs.freedesktop.org/show_bug.cgi?id=83772
Reviewed-by: Alban Crequy <alban.crequy@collabora.co.uk>

configure.ac

@@ -598,6 +598,10 @@ if test "x$ac_cv_header_syslog_h" = "xyes"; then
   AC_CHECK_DECLS([LOG_PERROR], [], [], [[#include <syslog.h>]])
 fi
 
+# For test-segfault.c
+AC_CHECK_HEADERS_ONCE([sys/prctl.h])
+AC_CHECK_FUNCS_ONCE([prctl raise])
+
 #### Check for broken poll; taken from Glib's configure
 
 AC_MSG_CHECKING([for broken poll])

test/test-segfault.c

@@ -9,18 +9,34 @@
 #include <sys/resource.h>
 #endif
 
+#ifdef HAVE_SYS_PRCTL_H
+#include <sys/prctl.h>
+#endif
+
 int
 main (int argc, char **argv)
 {
   char *p;  
 
 #if HAVE_SETRLIMIT
+  /* No core dumps please, we know we crashed. */
   struct rlimit r = { 0, };
   
   getrlimit (RLIMIT_CORE, &r);
   r.rlim_cur = 0;
   setrlimit (RLIMIT_CORE, &r);
-  
+#endif
+
+#if defined(HAVE_PRCTL) && defined(PR_SET_DUMPABLE)
+  /* Really, no core dumps please. On Linux, if core_pattern is
+   * set to a pipe (for abrt/apport/corekeeper/etc.), RLIMIT_CORE of 0
+   * is ignored (deliberately, so people can debug init(8) and other
+   * early stuff); but Linux has PR_SET_DUMPABLE, so we can avoid core
+   * dumps anyway. */
+  prctl (PR_SET_DUMPABLE, 0, 0, 0, 0);
+#endif
+
+#ifdef HAVE_RAISE
   raise (SIGSEGV);
 #endif
   p = NULL;