Support -plugin-opt=disable-output

LLVM plugin uses --plugin-opt=disable-output to disable output.
all_symbols_read_hook() calls exit() to disable output when
--plugin-opt=disable-output is passed to LLVM plugin.  This patch
registers plugin_cleanup() with atexit(), which removes output file
if --plugin-opt=disable-output is used.

	PR ld/17878
	* configure.ac: Check if atexit exists.
	* config.in: Regenerated.
	* configure: Likewise.
	* plugin.c (plugin_t): Add disable_output.
	(plugin_opt_plugin_arg): Set disable_output for disable-output.
	(plugin_cleanup): New.
	(plugin_load_plugins): Register plugin_cleanup() with atexit().

ld/config.in

@@ -17,6 +17,9 @@
 /* Define to choose default GOT handling scheme */
 #undef GOT_HANDLING_DEFAULT
 
+/* Define to 1 if you have the `atexit' function. */
+#undef HAVE_ATEXIT
+
 /* Define to 1 if you have the `close' function. */
 #undef HAVE_CLOSE
 

ld/configure

@@ -16549,6 +16549,18 @@ fi
 fi
 
 
+for ac_func in atexit
+do :
+  ac_fn_c_check_func "$LINENO" "atexit" "ac_cv_func_atexit"
+if test "x$ac_cv_func_atexit" = x""yes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_ATEXIT 1
+_ACEOF
+
+fi
+done
+
+
 for ac_header in stdlib.h unistd.h
 do :
   as_ac_Header=`$as_echo "ac_cv_header_$ac_header" | $as_tr_sh`

ld/configure.ac

@@ -195,6 +195,8 @@ AC_CHECK_FUNCS(glob mkstemp realpath sbrk setlocale waitpid)
 AC_CHECK_FUNCS(open lseek close)
 AC_HEADER_DIRENT
 
+AC_CHECK_FUNCS(atexit)
+
 dnl AC_CHECK_HEADERS(sys/mman.h)
 AC_FUNC_MMAP
 

ld/plugin.c

@@ -88,6 +88,8 @@ typedef struct plugin
   ld_plugin_cleanup_handler cleanup_handler;
   /* TRUE if the cleanup handlers have been called.  */
   bfd_boolean cleanup_done;
+  /* TRUE if output should be disabled.  */
+  bfd_boolean disable_output;
 } plugin_t;
 
 typedef struct view_buffer
@@ -283,6 +285,11 @@ plugin_opt_plugin_arg (const char *arg)
   *last_plugin_args_tail_chain_ptr = newarg;
   last_plugin_args_tail_chain_ptr = &newarg->next;
   last_plugin->n_args++;
+
+  /* LLVM plugin uses --plugin-opt=disable-output to disable output.  */
+  if (strcmp (arg, "disable-output") == 0)
+    last_plugin->disable_output = TRUE;
+
   return 0;
 }
 
@@ -934,6 +941,24 @@ set_tv_plugin_args (plugin_t *plugin, struct ld_plugin_tv *tv)
   tv->tv_u.tv_val = 0;
 }
 
+#if HAVE_ATEXIT
+static void
+plugin_cleanup (void)
+{
+  plugin_t *curplug = plugins_list;
+  while (curplug)
+    {
+      if (curplug->all_symbols_read_handler
+	  && curplug->disable_output)
+	{
+	  unlink_if_ordinary (output_filename);
+	  break;
+	}
+      curplug = curplug->next;
+    }
+}
+#endif
+
 /* Load up and initialise all plugins after argument parsing.  */
 void
 plugin_load_plugins (void)
@@ -994,6 +1019,12 @@ plugin_load_plugins (void)
 
   register_ld_plugin_object_p (plugin_object_p);
 
+#if HAVE_ATEXIT
+  /* Since all_symbols_read_hook() in LLVM plugin calls exit() to
+     disable output, we must register plugin_cleanup() with atexit().  */
+  atexit (plugin_cleanup);
+#endif
+
 #if HAVE_MMAP && HAVE_GETPAGESIZE
   plugin_pagesize = getpagesize ();;
 #endif