[cfe-commits] [patch] Don't mark libc++ functions as always_inline in debug mode.

[Howard Hinnant]

I'll start one.

Howard

On Feb 20, 2012, at 11:04 AM, Dave Zarzycki wrote:

> Howard,
> 
> Do we have libcxx FAQ somewhere? This question comes up from time to time and perhaps a FAQ entry would help.
> 
> davez
> 
> 
> On Feb 20, 2012, at 9:58 AM, Howard Hinnant <hhinnant at apple.com> wrote:
> 
>> This is more than just an optimization issue.  Experience with libstdc++ has shown a persistent ABI stability problem over the years with functions getting silently uninlined in one release of libstdc++.dylib and inlined in the next.  The best way to hold the ABI stable is to put inlining under my control, not the compielr's.
>> 
>> For those clients wishing to change these settings, <__config> was designed to defer to the client's wishes from the command line:
>> 
>> -D_LIBCPP_INLINE_VISIBILITY
>> 
>> will be used in preference to whatever <__config> says (or if it doesn't, that's the bug to fix).
>> 
>> Howard
>> 
>> On Feb 20, 2012, at 7:58 AM, Chris Lattner wrote:
>> 
>>> Why are these functions marked always-inline in the first place?
>>> 
>>> -Chris
>>> 
>>> On Feb 19, 2012, at 7:24 PM, Jeffrey Yasskin <jyasskin at gmail.com> wrote:
>>> 
>>>> Really, even if libc++ is bug-free, it'll confuse users if debugging
>>>> it in -O0 mode produces strange line jumps.
>>>> 
>>>> If NDEBUG is the wrong macro, would it make sense to provide a
>>>> LIBCXX_DEBUG flag to move the inlining decisions to clang?
>>>> 
>>>> On Sun, Feb 19, 2012 at 6:57 PM, Howard Hinnant <hhinnant at apple.com> wrote:
>>>>> On Feb 19, 2012, at 9:30 PM, Jeffrey Yasskin wrote:
>>>>> 
>>>>>> This patch may not be quite right, since the always_inline macros seem
>>>>>> to also have visibility effects, which this patch would block. I also
>>>>>> had to build with an explicit -UNDEBUG since cmake appears to add
>>>>>> -DNDEBUG regardless of whether the build mode requests it.
>>>>>> 
>>>>>> Jeffrey
>>>>>> <no_inline_debug.patch>
>>>>> 
>>>>> I can't commit this one.  The presumption is that NDEBUG is up to the client to turn on and off for his own purposes, and that libc++ does not need to be debugged by him.  I realize that libc++ has bugs.  But the goal is for it to not have bugs, and when it does need to be debugged, a libc++ developer such as myself will do it.
>>>>> 
>>>>> Howard
>>>>> 
>>>> 
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