From: Jennifer Yao <jenny.hyphen.fa@gmail.com>
To: Jonathan Wakely <jwakely@redhat.com>
Cc: libstdc++@gcc.gnu.org, gcc-patches@gcc.gnu.org
Subject: Re: [PATCH] Enable libstdc++ numeric conversions on Cygwin
Date: Thu, 12 Nov 2015 17:25:00 -0000 [thread overview]
Message-ID: <CAPQfdhnXQqZGypLpfnr19eYDMU7j+nhQTu1g=kCmfnAKxA9zeQ@mail.gmail.com> (raw)
In-Reply-To: <20151112145015.GD2937@redhat.com>
> On 12/11/15 13:39 +0000, Jonathan Wakely wrote:
>>
>> One downside of this change is that we introduce some (hopefully safe)
>> ODR violations, where inline functions and templates that depend on
>> _GLIBCXX_USE_C99_FOO might now be defined differently in C++98 and
>> C++11 code. Previously they had the same definition, even though in
>> C++11 mode the value of the _GLIBCXX_USE_C99_FOO macro might have been
>> sub-optimal (i.e. the C99 features were usable, but the macro said
>> they weren't). Those ODR violatiosn could be avoided if needed, by
>> always using the _GLIBCXX98_USE_C99_FOO macro in code that can be
>> included from either C++98 or C++11. We could still use the
>> _GLIBCXX11_USE_C99_FOO macro in pure C++11 code (such as the numeric
>> conversion functions) and get most of the benefit of this change.
>
>
> This patch (relative to the previous one) would avoid the ODR
> problems, by only using the C++98 macro in code that gets used in
> C++98 and later, and using the _GLIBCXX11_XXX ones in code that is
> never compiled as C++98 (specifically, the numeric conversion
> functions).
>
> Maybe this is a safer, more conservative change.
I haven't tested either of your patches yet (the testsuite runs
reeeeally slowly on Cygwin T___T), but I just wanted to express my
approval of the proposed changes (more specifically, the second patch
you posted).
Also, I was not aware that we had to worry about C++03 compatibility.
Sounds tedious.
next prev parent reply other threads:[~2015-11-12 17:25 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-18 15:19 Jennifer Yao
[not found] ` <CAPQfdhmMGJeb-tq29jTheoo5jUaeiFzcycWFTrpShRE-kPftGw@mail.gmail.com>
2015-09-18 15:51 ` Fwd: " Jonathan Wakely
2015-09-19 21:00 ` Jennifer Yao
2015-09-21 12:37 ` Jonathan Wakely
[not found] ` <CAPQfdh=uOjLzi60Dnd0Dd1ycJUDqMWQBCv1aRAGBP97DSUS3+Q@mail.gmail.com>
[not found] ` <20151112114049.GY2937@redhat.com>
2015-11-12 13:40 ` Jonathan Wakely
2015-11-12 14:50 ` Jonathan Wakely
2015-11-12 17:25 ` Jennifer Yao [this message]
2015-11-12 17:56 ` Jonathan Wakely
2015-11-12 22:56 ` Andreas Tobler
2015-11-13 14:52 ` Jonathan Wakely
2015-11-14 8:37 ` Christophe Lyon
2015-11-14 13:58 ` Jonathan Wakely
2015-11-14 21:23 ` Jennifer Yao
2015-11-15 21:38 ` Jennifer Yao
2015-11-16 9:48 ` Jonathan Wakely
2015-11-14 16:32 ` Jonathan Wakely
2015-11-15 8:58 ` Christophe Lyon
2015-11-15 11:14 ` Jonathan Wakely
2015-11-15 16:25 ` Christophe Lyon
2015-12-08 10:59 ` Alan Lawrence
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