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Clarify interaction of -Wnarrowing with -std

Message ID 20170327220110.GT4425@redhat.com
State New
Headers show

Commit Message

Jonathan Wakely March 27, 2017, 10:01 p.m. UTC 
On 27/03/17 10:09 +0100, Jonathan Wakely wrote:
>On 26/03/17 14:32 -0600, Sandra Loosemore wrote:
>>On 03/26/2017 02:13 PM, Gerald Pfeifer wrote:
>>>Hi Jonathan,
>>>
>>>On Tue, 23 Feb 2016, Jonathan Wakely wrote:
>>>>On 19/02/16 13:17 -0700, Sandra Loosemore wrote:
>>>>>I suppose the patch is OK as it stands, but I was going to suggest
>>>>>restructuring it so that it talks about the default behavior first
>>>>>and what
>>>>>it does with non-default -std= options after that, instead of
>>>>>vice-versa.
>>>>>Unfortunately I am backlogged on other things right now and it might
>>>>>take me
>>>>>a day or two before I have time to come up with some alternate
>>>>>wording.  If
>>>>>we are in a rush, go ahead and commit the existing patch meanwhile, I
>>>>>guess.
>>>>Is this better?
>>>
>>>I believe your follow-up patch did not get committed, nor did I
>>>see any response from anyone.
>>>
>>>To me it looks fine.  Did you hold of intentionally, or did this
>>>get lost for lack of responses?
>>>
>>>Sandra, what do you think?
>>
>>Looks OK to me.  I apologize for losing track of this patch previously.  :-(
>
>OK, thanks, I'll commit it today.

I've committed the attached patch.
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Patch

commit 77d4b96ba46e57a761e6844b89de9412011ef583
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Mon Mar 27 19:37:01 2017 +0100

    Restructure -Wno-narrowing documentation
    
    	* doc/invoke.texi (-Wno-narrowing): Reorder so default behavior is
    	covered first.

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 3f0eb2f..8d3821e 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -2869,10 +2869,17 @@  During the link-time optimization warn about type mismatches in
 global declarations from different compilation units.
 Requires @option{-flto} to be enabled.  Enabled by default.
 
-@item -Wnarrowing @r{(C++ and Objective-C++ only)}
+@item -Wno-narrowing @r{(C++ and Objective-C++ only)}
 @opindex Wnarrowing
 @opindex Wno-narrowing
-With @option{-std=gnu++98} or @option{-std=c++98}, warn when a narrowing
+For C++11 and later standards, narrowing conversions are diagnosed by default,
+as required by the standard.  A narrowing conversion from a constant produces
+an error, and a narrowing conversion from a non-constant produces a warning,
+but @option{-Wno-narrowing} suppresses the diagnostic.
+Note that this does not affect the meaning of well-formed code;
+narrowing conversions are still considered ill-formed in SFINAE contexts.
+
+With @option{-Wnarrowing} in C++98, warn when a narrowing
 conversion prohibited by C++11 occurs within
 @samp{@{ @}}, e.g.
 
@@ -2882,14 +2889,6 @@  int i = @{ 2.2 @}; // error: narrowing from double to int
 
 This flag is included in @option{-Wall} and @option{-Wc++11-compat}.
 
-When a later standard is in effect, e.g. when using @option{-std=c++11},
-narrowing conversions are diagnosed by default, as required by the standard.
-A narrowing conversion from a constant produces an error,
-and a narrowing conversion from a non-constant produces a warning,
-but @option{-Wno-narrowing} suppresses the diagnostic.
-Note that this does not affect the meaning of well-formed code;
-narrowing conversions are still considered ill-formed in SFINAE contexts.
-
 @item -Wnoexcept @r{(C++ and Objective-C++ only)}
 @opindex Wnoexcept
 @opindex Wno-noexcept