re PR lto/61886 (LTO breaks fread with _FORTIFY_SOURCE=2)

	PR ipa/61886
	* lto-symtab.c (lto_symtab_merge_p): Avoid merging across different
	values of error and warning attributes.
	* gcc.dg/lto/pr61886_0.c: New testcase

From-SVN: r231548

gcc/lto/ChangeLog

+2015-12-11  Jan Hubicka  <hubicka@ucw.cz>
+
+	PR ipa/61886
+	* lto-symtab.c (lto_symtab_merge_p): Avoid merging across different
+	values of error and warning attributes.
+
 2015-12-08  Jan Hubicka  <hubicka@ucw.cz>
 
 	PR lto/68811

gcc/lto/lto-symtab.c

@@ -511,19 +511,59 @@ static bool
 lto_symtab_merge_p (tree prevailing, tree decl)
 {
   if (TREE_CODE (prevailing) != TREE_CODE (decl))
-    return false;
+    {
+      if (symtab->dump_file)
+	fprintf (symtab->dump_file, "Not merging decls; "
+		 "TREE_CODE mismatch\n");
+      return false;
+    }
   if (TREE_CODE (prevailing) == FUNCTION_DECL)
     {
       if (DECL_BUILT_IN (prevailing) != DECL_BUILT_IN (decl))
-	return false;
+	{
+          if (symtab->dump_file)
+	    fprintf (symtab->dump_file, "Not merging decls; "
+		     "DECL_BUILT_IN mismatch\n");
+	  return false;
+	}
       if (DECL_BUILT_IN (prevailing)
 	  && (DECL_BUILT_IN_CLASS (prevailing) != DECL_BUILT_IN_CLASS (decl)
 	      || DECL_FUNCTION_CODE (prevailing) != DECL_FUNCTION_CODE (decl)))
-	return false;
+	{
+          if (symtab->dump_file)
+	    fprintf (symtab->dump_file, "Not merging decls; "
+		     "DECL_BUILT_IN_CLASS or CODE mismatch\n");
+	  return false;
+	}
+    }
+  if (DECL_ATTRIBUTES (prevailing) != DECL_ATTRIBUTES (decl))
+    {
+      tree prev_attr = lookup_attribute ("error", DECL_ATTRIBUTES (prevailing));
+      tree attr = lookup_attribute ("error", DECL_ATTRIBUTES (decl));
+      if ((prev_attr == NULL) != (attr == NULL)
+	  || (prev_attr
+	      && TREE_VALUE (TREE_VALUE (prev_attr))
+		 != TREE_VALUE (TREE_VALUE (attr))))
+	{
+          if (symtab->dump_file)
+	    fprintf (symtab->dump_file, "Not merging decls; "
+		     "error attribute mismatch\n");
+	  return false;
+	}
+
+      prev_attr = lookup_attribute ("warning", DECL_ATTRIBUTES (prevailing));
+      attr = lookup_attribute ("warning", DECL_ATTRIBUTES (decl));
+      if ((prev_attr == NULL) != (attr == NULL)
+	  || (prev_attr
+	      && TREE_VALUE (TREE_VALUE (prev_attr))
+		 != TREE_VALUE (TREE_VALUE (attr))))
+	{
+          if (symtab->dump_file)
+	    fprintf (symtab->dump_file, "Not merging decls; "
+		     "warning attribute mismatch\n");
+	  return false;
+	}
     }
-  /* There are several other cases where merging can not be done, but until
-     aliasing code is fixed to support aliases it we can not really return
-     false on non-readonly var, yet.  */
   return true;
 }
 

gcc/testsuite/ChangeLog

+2015-12-11  Jan Hubicka  <hubicka@ucw.cz>
+
+	PR ipa/61886
+	* gcc.dg/lto/pr61886_0.c: New testcase
+
 2015-12-10  Jan Hubicka  <hubicka@ucw.cz>
 
 	* gcc.c-torture/execute/20010122-1.c: Disable cloning.

gcc/testsuite/gcc.dg/lto/pr61886_0.c

+/* { dg-lto-do link } */
+/* { dg-lto-options { { -flto -O2 -Werror } } } */
+
+typedef __SIZE_TYPE__ size_t;
+typedef struct _IO_FILE FILE;
+
+extern size_t __fread_chk (void *__restrict __ptr, size_t __ptrlen, size_t __size, size_t __n, FILE *__restrict __stream) __asm__ ("" "__fread_chk")      __attribute__ ((__warn_unused_result__));
+extern size_t __fread_chk_warn (void *__restrict __ptr, size_t __ptrlen, size_t __size, size_t __n, FILE *__restrict __stream) __asm__ ("" "__fread_chk")      __attribute__ ((__warn_unused_result__)) __attribute__((__warning__ ("fread called with bigger size * nmemb than length " "of destination buffer")));
+
+extern __inline __attribute__ ((__always_inline__)) __attribute__ ((__gnu_inline__)) __attribute__ ((__artificial__)) __attribute__ ((__warn_unused_result__))
+size_t
+fread (void *__restrict __ptr, size_t __size, size_t __n,
+       FILE *__restrict __stream)
+{
+  if (__builtin_object_size (__ptr, 0) != (size_t) -1)
+    {
+      if (!__builtin_constant_p (__size)
+          || !__builtin_constant_p (__n)
+          || (__size | __n) >= (((size_t) 1) << (8 * sizeof (size_t) / 2)))
+        return __fread_chk (__ptr, __builtin_object_size (__ptr, 0), __size, __n, __stream);
+      if (__size * __n > __builtin_object_size (__ptr, 0))
+        return __fread_chk_warn (__ptr, __builtin_object_size (__ptr, 0), __size, __n, __stream);
+    }
+}
+
+volatile size_t nmemb;
+FILE *fp;
+int main ()
+{
+  char file_contents[4096];
+  /* We shouldn't get this resolved to a call to __fread_chk_warn.  */
+  return fread (file_contents, 1, nmemb, fp);
+}