Properly detect working jobserver in gcc driver.

2019-08-02  Martin Liska  <mliska@suse.cz>

	PR lto/91313
	* gcc.c (driver::maybe_run_linker): Call detect_jobserver
	to detect working job server.
	(driver::detect_jobserver): Test whether jobserver
	is active from GCC driver. That will prevent situation where
	GCC is invoked from a LD plugin and the linker already uses
	file descriptors suggested by make.  That leads to a wrong
	detection.
	* gcc.h (driver): Add detect_jobserver.
	* lto-wrapper.c (jobserver_active_p): Simplify sscanf by
	not scanning for --jobserver-auth prefix.

From-SVN: r274003

gcc/ChangeLog

@@ -1,3 +1,17 @@
+2019-08-02  Martin Liska  <mliska@suse.cz>
+
+	PR lto/91313
+	* gcc.c (driver::maybe_run_linker): Call detect_jobserver
+	to detect working job server.
+	(driver::detect_jobserver): Test whether jobserver
+	is active from GCC driver. That will prevent situation where
+	GCC is invoked from a LD plugin and the linker already uses
+	file descriptors suggested by make.  That leads to a wrong
+	detection.
+	* gcc.h (driver): Add detect_jobserver.
+	* lto-wrapper.c (jobserver_active_p): Simplify sscanf by
+	not scanning for --jobserver-auth prefix.
+
 2019-08-02  Jakub Jelinek  <jakub@redhat.com>
 
 	PR tree-optimization/91201

gcc/gcc.c

@@ -8268,6 +8268,8 @@ driver::maybe_run_linker (const char *argv0) const
     {
       int tmp = execution_count;
 
+      detect_jobserver ();
+
       if (! have_c)
 	{
 #if HAVE_LTO_PLUGIN > 0
@@ -8357,6 +8359,46 @@ driver::final_actions () const
     }
 }
 
+/* Detect whether jobserver is active and working.  If not drop
+   --jobserver-auth from MAKEFLAGS.  */
+
+void
+driver::detect_jobserver () const
+{
+  /* Detect jobserver and drop it if it's not working.  */
+  const char *makeflags = env.get ("MAKEFLAGS");
+  if (makeflags != NULL)
+    {
+      const char *needle = "--jobserver-auth=";
+      const char *n = strstr (makeflags, needle);
+      if (n != NULL)
+	{
+	  int rfd = -1;
+	  int wfd = -1;
+
+	  bool jobserver
+	    = (sscanf (n + strlen (needle), "%d,%d", &rfd, &wfd) == 2
+	       && rfd > 0
+	       && wfd > 0
+	       && fcntl (rfd, F_GETFD) >= 0
+	       && fcntl (wfd, F_GETFD) >= 0);
+
+	  /* Drop the jobserver if it's not working now.  */
+	  if (!jobserver)
+	    {
+	      unsigned offset = n - makeflags;
+	      char *dup = xstrdup (makeflags);
+	      dup[offset] = '\0';
+
+	      const char *space = strchr (makeflags + offset, ' ');
+	      if (space != NULL)
+		strcpy (dup + offset, space);
+	      xputenv (concat ("MAKEFLAGS=", dup, NULL));
+	    }
+	}
+    }
+}
+
 /* Determine what the exit code of the driver should be.  */
 
 int

gcc/gcc.h

@@ -51,6 +51,7 @@ class driver
   void do_spec_on_infiles () const;
   void maybe_run_linker (const char *argv0) const;
   void final_actions () const;
+  void detect_jobserver () const;
   int get_exit_code () const;
 
  private:

gcc/lto-wrapper.c

@@ -1234,7 +1234,7 @@ jobserver_active_p (void)
   int rfd = -1;
   int wfd = -1;
 
-  return ((sscanf(n, "--jobserver-auth=%d,%d", &rfd, &wfd) == 2)
+  return (sscanf (n + strlen (needle), "%d,%d", &rfd, &wfd) == 2
 	  && rfd > 0
 	  && wfd > 0
 	  && fcntl (rfd, F_GETFD) >= 0