Patchwork Bootstrap failure in tree-object-size.c due to -Wnarrowing (was: [C++ Patch] PR 50810)

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Submitter Paolo Carlini
Date Oct. 24, 2011, 12:56 a.m.
Message ID <4EA4B7A8.1060507@oracle.com>
Download mbox | patch
Permalink /patch/121261/
State New
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Comments

Paolo Carlini - Oct. 24, 2011, 12:56 a.m.
... and the patch ;)

Paolo.

////////////////
/c-family
2011-10-23  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/50810
	* c-opts.c (c_common_handle_option): Do not enable -Wc++0x-compat
	as part of -Wall; handle -Wc++0x-compat.
	(c_common_post_options): -std=c++0x enables -Wnarrowing.
	* c.opt ([Wnarrowing]): Update.

/cp
2011-10-23  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/50810
	* typeck2.c (check_narrowing): Adjust OPT_Wnarrowing diagnostics.
	(digest_init_r): Call check_narrowing irrespective of the C++ dialect.
	* decl.c (check_initializer): Likewise.
	* semantics.c (finish_compound_literal): Likewise.

/testsuite
2011-10-23  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/50810
	* g++.dg/cpp0x/warn_cxx0x2.C: New.
	* g++.dg/cpp0x/warn_cxx0x3.C: Likewise.

2011-10-23  Paolo Carlini  <paolo.carlini@oracle.com>

	PR c++/50810
	* doc/invoke.texi ([-Wall], [-Wnarrowing], [-Wc++0x-compat]): Update.
Gabriel Dos Reis - Oct. 24, 2011, 1:30 a.m.
On Sun, Oct 23, 2011 at 7:56 PM, Paolo Carlini <paolo.carlini@oracle.com> wrote:
> ... and the patch ;)

I am bit puzzled by this:

+This flag is included in @option{-Wc++0x-compat}.
+With -std=c++0x, @option{-Wno-narrowing} suppresses the diagnostic
+required by the standard.

and this:
-  /* If we're allowing C++0x constructs, don't warn about C++0x
-     compatibility problems.  */
   if (cxx_dialect == cxx0x)
-    warn_cxx0x_compat = 0;
+    {
+      /* If we're allowing C++0x constructs, don't warn about C++98
+	 identifiers which are keywords in C++0x.  */
+      warn_cxx0x_compat = 0;

+      if (warn_narrowing == -1)
+	warn_narrowing = 1;
+    }




We do not use -W or -Wno- to suppressed *required* diagnostics.  So,
when -std=c++0x,
-Wno-narrowing should not have any effect.  However with
-Wc++0x-compat, it could
make sense to have -Wno-narrowing suppress the diagnostic.

The point is this:  we do not use -W flags to change a standards semantics.
But we use -W to make suggestions (e.g. warnings) so a suggesting should be
suppressed only in the context of another suggestion (-Wc++0x-compat.)
Paolo Carlini - Oct. 24, 2011, 1:48 a.m.
Hi,

On 10/24/2011 03:30 AM, Gabriel Dos Reis wrote:
> We do not use -W or -Wno- to suppressed *required* diagnostics. So, 
> when -std=c++0x, -Wno-narrowing should not have any effect.
Personally, I have no problem with this, but note, I'm not inventing 
anything new here, the behavior you are discussing *pre*-dates my patch 
and I feel a little nervous about changing it. If you think you can 
approve this part of rhe patch, I'll change it as you want and resend.

Paolo.
Gabriel Dos Reis - Oct. 24, 2011, 2:10 a.m.
On Sun, Oct 23, 2011 at 8:48 PM, Paolo Carlini <paolo.carlini@oracle.com> wrote:
> Hi,
>
> On 10/24/2011 03:30 AM, Gabriel Dos Reis wrote:
>>
>> We do not use -W or -Wno- to suppressed *required* diagnostics. So, when
>> -std=c++0x, -Wno-narrowing should not have any effect.
>
> Personally, I have no problem with this, but note, I'm not inventing
> anything new here, the behavior you are discussing *pre*-dates my patch and
> I feel a little nervous about changing it. If you think you can approve this
> part of rhe patch, I'll change it as you want and resend.

Let me quote again the part of the patch under discussion:

-  /* If we're allowing C++0x constructs, don't warn about C++0x
-     compatibility problems.  */
   if (cxx_dialect == cxx0x)
-    warn_cxx0x_compat = 0;
+    {
+      /* If we're allowing C++0x constructs, don't warn about C++98
+	 identifiers which are keywords in C++0x.  */
+      warn_cxx0x_compat = 0;

+      if (warn_narrowing == -1)
+	warn_narrowing = 1;
+    }
+  else if (warn_narrowing == -1)
+    warn_narrowing = 0;
+

Before the patch, -std=c++0x effectively put off -Wc++0x-compat because we
are compiling c++98/c++03 code, so we can only *warn* about possible
compatibility conflict with C++11.   However, the narrowing diagnostic required
by C++11 is NOT a warning.  It is a diagnostic.  The way we alter a standard
mandate is through some -fflag, e.g. -fpermissive.

What the above patch fragment is doing is to turn on a *warning*.
When -std=c++0x
is in effect, narrowing is no longer a warning.  It is an error by default.
Paolo Carlini - Oct. 24, 2011, 2:16 a.m.
On 10/24/2011 04:10 AM, Gabriel Dos Reis wrote:
> Before the patch, -std=c++0x effectively put off -Wc++0x-compat 
> because we are compiling c++98/c++03 code, so we can only *warn* about 
> possible compatibility conflict with C++11. However, the narrowing 
> diagnostic required by C++11 is NOT a warning. It is a diagnostic. The 
> way we alter a standard mandate is through some -fflag, e.g. 
> -fpermissive. What the above patch fragment is doing is to turn on a 
> *warning*. When -std=c++0x is in effect, narrowing is no longer a 
> warning. It is an error by default.
I'm missing your point, I'm sorry: I maintain that *before* and after 
the patch -Wno-narrowing in C++0x mode was able to suppress the 
narrowing warnings. I'm 100% sure, I double checked for you one second 
ago. Are we on the same page on this? If we are, and you think gcc 
should do something new, I have no problem changing my patch to, eg:

   if (cxx_dialect == cxx0x)
     {
       /* If we're allowing C++0x constructs, don't warn about C++98
      identifiers which are keywords in C++0x.  */
       warn_cxx0x_compat = 0;
       warn_narrowing = 1;
     }
   else if (warn_narrowing == -1)
     warn_narrowing = 0;

Paolo.
Gabriel Dos Reis - Oct. 24, 2011, 4:02 a.m.
On Sun, Oct 23, 2011 at 9:16 PM, Paolo Carlini <paolo.carlini@oracle.com> wrote:
> On 10/24/2011 04:10 AM, Gabriel Dos Reis wrote:
>>
>> Before the patch, -std=c++0x effectively put off -Wc++0x-compat because we
>> are compiling c++98/c++03 code, so we can only *warn* about possible
>> compatibility conflict with C++11. However, the narrowing diagnostic
>> required by C++11 is NOT a warning. It is a diagnostic. The way we alter a
>> standard mandate is through some -fflag, e.g. -fpermissive. What the above
>> patch fragment is doing is to turn on a *warning*. When -std=c++0x is in
>> effect, narrowing is no longer a warning. It is an error by default.
>
> I'm missing your point, I'm sorry: I maintain that *before* and after the
> patch -Wno-narrowing in C++0x mode was able to suppress the narrowing
> warnings.

and I am saying that is a bug.

> 'm 100% sure, I double checked for you one second ago. Are we on
> the same page on this? If we are, and you think gcc should do something new,

It is new only in the sense that a bug will be fixed.  Otherwise no,
it is not new.

> I have no problem changing my patch to, eg:
>
>  if (cxx_dialect == cxx0x)
>    {
>      /* If we're allowing C++0x constructs, don't warn about C++98
>     identifiers which are keywords in C++0x.  */
>      warn_cxx0x_compat = 0;
>      warn_narrowing = 1;
>    }

Yes, a -Wno-narrowing should not suppress narrowing in C++11 mode.

>  else if (warn_narrowing == -1)
>    warn_narrowing = 0;
>

OK.

Patch

Index: doc/invoke.texi
===================================================================
--- doc/invoke.texi	(revision 180348)
+++ doc/invoke.texi	(working copy)
@@ -2365,17 +2365,18 @@  an instance of a derived class through a pointer t
 base class does not have a virtual destructor.  This warning is enabled
 by @option{-Wall}.
 
-@item -Wno-narrowing @r{(C++ and Objective-C++ only)}
+@item -Wnarrowing @r{(C++ and Objective-C++ only)}
 @opindex Wnarrowing
 @opindex Wno-narrowing
-With -std=c++0x, suppress the diagnostic required by the standard for
-narrowing conversions within @samp{@{ @}}, e.g.
+Warn when a narrowing conversion occurs within @samp{@{ @}}, e.g.
 
 @smallexample
 int i = @{ 2.2 @}; // error: narrowing from double to int
 @end smallexample
 
-This flag can be useful for compiling valid C++98 code in C++0x mode
+This flag is included in @option{-Wc++0x-compat}.
+With -std=c++0x, @option{-Wno-narrowing} suppresses the diagnostic
+required by the standard.
 
 @item -Wnoexcept @r{(C++ and Objective-C++ only)}
 @opindex Wnoexcept
@@ -2993,7 +2994,6 @@  Options} and @ref{Objective-C and Objective-C++ Di
 
 @gccoptlist{-Waddress   @gol
 -Warray-bounds @r{(only with} @option{-O2}@r{)}  @gol
--Wc++0x-compat  @gol
 -Wchar-subscripts  @gol
 -Wenum-compare @r{(in C/Objc; this is on by default in C++)} @gol
 -Wimplicit-int @r{(C and Objective-C only)} @gol
@@ -4066,7 +4066,7 @@  ISO C and ISO C++, e.g.@: request for implicit con
 @item -Wc++0x-compat @r{(C++ and Objective-C++ only)}
 Warn about C++ constructs whose meaning differs between ISO C++ 1998 and
 ISO C++ 200x, e.g., identifiers in ISO C++ 1998 that will become keywords
-in ISO C++ 200x.  This warning is enabled by @option{-Wall}.
+in ISO C++ 200x.  This warning turns on @option{-Wnarrowing}.
 
 @item -Wcast-qual
 @opindex Wcast-qual
Index: c-family/c.opt
===================================================================
--- c-family/c.opt	(revision 180348)
+++ c-family/c.opt	(working copy)
@@ -490,8 +490,8 @@  C ObjC C++ ObjC++ Warning
 Warn about use of multi-character character constants
 
 Wnarrowing
-C ObjC C++ ObjC++ Warning Var(warn_narrowing) Init(1)
--Wno-narrowing	  In C++0x mode, ignore ill-formed narrowing conversions within { }
+C ObjC C++ ObjC++ Warning Var(warn_narrowing) Init(-1) Warning
+Warn about ill-formed narrowing conversions within { }
 
 Wnested-externs
 C ObjC Var(warn_nested_externs) Warning
Index: c-family/c-opts.c
===================================================================
--- c-family/c-opts.c	(revision 180348)
+++ c-family/c-opts.c	(working copy)
@@ -404,7 +404,6 @@  c_common_handle_option (size_t scode, const char *
 	  /* C++-specific warnings.  */
           warn_sign_compare = value;
 	  warn_reorder = value;
-          warn_cxx0x_compat = value;
           warn_delnonvdtor = value;
 	}
 
@@ -436,6 +435,10 @@  c_common_handle_option (size_t scode, const char *
       cpp_opts->warn_cxx_operator_names = value;
       break;
 
+    case OPT_Wc__0x_compat:
+      warn_narrowing = value;
+      break;
+
     case OPT_Wdeprecated:
       cpp_opts->cpp_warn_deprecated = value;
       break;
@@ -997,11 +1000,18 @@  c_common_post_options (const char **pfilename)
   if (warn_implicit_function_declaration == -1)
     warn_implicit_function_declaration = flag_isoc99;
 
-  /* If we're allowing C++0x constructs, don't warn about C++0x
-     compatibility problems.  */
   if (cxx_dialect == cxx0x)
-    warn_cxx0x_compat = 0;
+    {
+      /* If we're allowing C++0x constructs, don't warn about C++98
+	 identifiers which are keywords in C++0x.  */
+      warn_cxx0x_compat = 0;
 
+      if (warn_narrowing == -1)
+	warn_narrowing = 1;
+    }
+  else if (warn_narrowing == -1)
+    warn_narrowing = 0;
+
   if (flag_preprocess_only)
     {
       /* Open the output now.  We must do so even if flag_no_output is
Index: testsuite/g++.dg/cpp0x/warn_cxx0x2.C
===================================================================
--- testsuite/g++.dg/cpp0x/warn_cxx0x2.C	(revision 0)
+++ testsuite/g++.dg/cpp0x/warn_cxx0x2.C	(revision 0)
@@ -0,0 +1,4 @@ 
+// PR c++/50810
+// { dg-options "-std=gnu++98 -Wc++0x-compat" }
+
+signed char data[] = { 0xff }; // { dg-warning "narrowing" }
Index: testsuite/g++.dg/cpp0x/warn_cxx0x3.C
===================================================================
--- testsuite/g++.dg/cpp0x/warn_cxx0x3.C	(revision 0)
+++ testsuite/g++.dg/cpp0x/warn_cxx0x3.C	(revision 0)
@@ -0,0 +1,4 @@ 
+// PR c++/50810
+// { dg-options "-std=gnu++98 -Wc++0x-compat -Wno-narrowing" }
+
+signed char data[] = { 0xff };
Index: cp/decl.c
===================================================================
--- cp/decl.c	(revision 180348)
+++ cp/decl.c	(working copy)
@@ -5523,7 +5523,7 @@  check_initializer (tree decl, tree init, int flags
 	  else
 	    {
 	      init = reshape_init (type, init, tf_warning_or_error);
-	      if (cxx_dialect >= cxx0x && SCALAR_TYPE_P (type))
+	      if (SCALAR_TYPE_P (type))
 		check_narrowing (type, init);
 	    }
 	}
Index: cp/typeck2.c
===================================================================
--- cp/typeck2.c	(revision 180348)
+++ cp/typeck2.c	(working copy)
@@ -803,8 +803,10 @@  check_narrowing (tree type, tree init)
     }
 
   if (!ok)
-    pedwarn (input_location, OPT_Wnarrowing, "narrowing conversion of %qE "
-	     "from %qT to %qT inside { }", init, ftype, type);
+    emit_diagnostic ((cxx_dialect != cxx98) ? DK_PEDWARN : DK_WARNING,
+		     input_location, OPT_Wnarrowing,
+		     "narrowing conversion of %qE from %qT to %qT inside { }",
+		     init, ftype, type);
 }
 
 /* Process the initializer INIT for a variable of type TYPE, emitting
@@ -901,7 +903,7 @@  digest_init_r (tree type, tree init, bool nested,
     {
       tree *exp;
 
-      if (cxx_dialect != cxx98 && nested)
+      if (nested)
 	check_narrowing (type, init);
       init = convert_for_initialization (0, type, init, flags,
 					 ICR_INIT, NULL_TREE, 0,
Index: cp/semantics.c
===================================================================
--- cp/semantics.c	(revision 180348)
+++ cp/semantics.c	(working copy)
@@ -2369,7 +2369,7 @@  finish_compound_literal (tree type, tree compound_
       && check_array_initializer (NULL_TREE, type, compound_literal))
     return error_mark_node;
   compound_literal = reshape_init (type, compound_literal, complain);
-  if (cxx_dialect >= cxx0x && SCALAR_TYPE_P (type)
+  if (SCALAR_TYPE_P (type)
       && !BRACE_ENCLOSED_INITIALIZER_P (compound_literal))
     check_narrowing (type, compound_literal);
   if (TREE_CODE (type) == ARRAY_TYPE