[C PATCH] Make -Wno-implicit-int work in C99 mode

[Marek Polacek <polacek at redhat dot com>]

C99 mode warns about defaulting to int by default, but without
the possibility to suppress the warning with -Wno-implicit-int.
This is likely to arouse the ire of the users, especially with
the new default.

Therefore the following patch tweaks warn_implicit_int in such
a way that -Wimplicit and -Wimplicit-int should work as intended
(following the rule that more specific option takes precedence
over the less specific).  There should be no changes in GNU89
mode.

Bootstrapped/regtested on x86_64-linux, ok for trunk?

2014-10-17  Marek Polacek  <polacek@redhat.com>

c-family/
	* c-opts.c (c_common_post_options): Set warn_implicit_int.
	* c.opt (Wimplicit-int): Initialize to -1.
c/
	* c-decl.c (grokdeclarator): Use OPT_Wimplicit_int unconditionally.
	(start_function): Use OPT_Wimplicit_int instead of 0.
	(store_parm_decls_oldstyle): Likewise.
testsuite/
	* gcc.dg/Wimplicit-int-1.c: New test.
	* gcc.dg/Wimplicit-int-2.c: New test.
	* gcc.dg/Wimplicit-int-3.c: New test.
	* gcc.dg/Wimplicit-int-4.c: New test.

diff --git gcc/c-family/c-opts.c gcc/c-family/c-opts.c
index eb078e3..448eb3e 100644
--- gcc/c-family/c-opts.c
+++ gcc/c-family/c-opts.c
@@ -864,6 +864,10 @@ c_common_post_options (const char **pfilename)
   if (warn_implicit_function_declaration == -1)
     warn_implicit_function_declaration = flag_isoc99;
 
+  /* -Wimplicit-int is enabled by default for C99.  */
+  if (warn_implicit_int == -1)
+    warn_implicit_int = flag_isoc99;
+
   /* Declone C++ 'structors if -Os.  */
   if (flag_declone_ctor_dtor == -1)
     flag_declone_ctor_dtor = optimize_size;
diff --git gcc/c-family/c.opt gcc/c-family/c.opt
index 72ac2ed..4f96cf8 100644
--- gcc/c-family/c.opt
+++ gcc/c-family/c.opt
@@ -488,7 +488,7 @@ C ObjC Var(warn_implicit_function_declaration) Init(-1) Warning LangEnabledBy(C
 Warn about implicit function declarations
 
 Wimplicit-int
-C ObjC Var(warn_implicit_int) Warning LangEnabledBy(C ObjC,Wimplicit)
+C ObjC Var(warn_implicit_int) Init(-1) Warning LangEnabledBy(C ObjC,Wimplicit)
 Warn when a declaration does not specify a type
 
 Wimport
diff --git gcc/c/c-decl.c gcc/c/c-decl.c
index 839c67b..b18da48 100644
--- gcc/c/c-decl.c
+++ gcc/c/c-decl.c
@@ -5330,11 +5330,11 @@ grokdeclarator (const struct c_declarator *declarator,
       else
 	{
 	  if (name)
-	    warn_defaults_to (loc, flag_isoc99 ? 0 : OPT_Wimplicit_int,
+	    warn_defaults_to (loc, OPT_Wimplicit_int,
 			      "type defaults to %<int%> in declaration "
 			      "of %qE", name);
 	  else
-	    warn_defaults_to (loc, flag_isoc99 ? 0 : OPT_Wimplicit_int,
+	    warn_defaults_to (loc, OPT_Wimplicit_int,
 			      "type defaults to %<int%> in type name");
 	}
     }
@@ -8120,7 +8120,7 @@ start_function (struct c_declspecs *declspecs, struct c_declarator *declarator,
     }
 
   if (warn_about_return_type)
-    warn_defaults_to (loc, flag_isoc99 ? 0
+    warn_defaults_to (loc, flag_isoc99 ? OPT_Wimplicit_int
 			   : (warn_return_type ? OPT_Wreturn_type
 			      : OPT_Wimplicit_int),
 		      "return type defaults to %<int%>");
@@ -8429,7 +8429,8 @@ store_parm_decls_oldstyle (tree fndecl, const struct c_arg_info *arg_info)
 
 	  if (flag_isoc99)
 	    pedwarn (DECL_SOURCE_LOCATION (decl),
-		     0, "type of %qD defaults to %<int%>", decl);
+		     OPT_Wimplicit_int, "type of %qD defaults to %<int%>",
+		     decl);
 	  else
 	    warning_at (DECL_SOURCE_LOCATION (decl),
 			OPT_Wmissing_parameter_type,
diff --git gcc/testsuite/gcc.dg/Wimplicit-int-1.c gcc/testsuite/gcc.dg/Wimplicit-int-1.c
index e69de29..0c89caf 100644
--- gcc/testsuite/gcc.dg/Wimplicit-int-1.c
+++ gcc/testsuite/gcc.dg/Wimplicit-int-1.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+static l; /* { dg-warning "type defaults to" } */
+
+foo (a) /* { dg-warning "return type defaults to" } */
+/* { dg-warning "type of .a. defaults to .int." "type" { target *-*-* } 6 } */
+{
+  auto p; /* { dg-warning "type defaults to" } */
+  typedef bar; /* { dg-warning "type defaults to" } */
+}
diff --git gcc/testsuite/gcc.dg/Wimplicit-int-2.c gcc/testsuite/gcc.dg/Wimplicit-int-2.c
index e69de29..158b61c 100644
--- gcc/testsuite/gcc.dg/Wimplicit-int-2.c
+++ gcc/testsuite/gcc.dg/Wimplicit-int-2.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-pedantic-errors" } */
+
+static l; /* { dg-error "type defaults to" } */
+
+foo (a) /* { dg-error "return type defaults to" } */
+/* { dg-error "type of .a. defaults to .int." "type" { target *-*-* } 6 } */
+{
+  auto p; /* { dg-error "type defaults to" } */
+  typedef bar; /* { dg-error "type defaults to" } */
+}
diff --git gcc/testsuite/gcc.dg/Wimplicit-int-3.c gcc/testsuite/gcc.dg/Wimplicit-int-3.c
index e69de29..654ce73 100644
--- gcc/testsuite/gcc.dg/Wimplicit-int-3.c
+++ gcc/testsuite/gcc.dg/Wimplicit-int-3.c
@@ -0,0 +1,10 @@
+/* { dg-do compile } */
+/* { dg-options "-pedantic-errors -Wno-implicit-int" } */
+
+static l;
+
+foo (a)
+{
+  auto p;
+  typedef bar;
+}
diff --git gcc/testsuite/gcc.dg/Wimplicit-int-4.c gcc/testsuite/gcc.dg/Wimplicit-int-4.c
index e69de29..b2528356 100644
--- gcc/testsuite/gcc.dg/Wimplicit-int-4.c
+++ gcc/testsuite/gcc.dg/Wimplicit-int-4.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-Wno-implicit -Wimplicit-int" } */
+
+static l; /* { dg-warning "type defaults to" } */
+
+foo (a) /* { dg-warning "return type defaults to" } */
+/* { dg-warning "type of .a. defaults to .int." "type" { target *-*-* } 6 } */
+{
+  auto p; /* { dg-warning "type defaults to" } */
+  typedef bar; /* { dg-warning "type defaults to" } */
+}

	Marek