[Boost-build] Turn on _GLIBCXX_DEBUG with <runtime-debugging>on (was: Trivial issues have been neglected.)

Subject: [Boost-build] Turn on _GLIBCXX_DEBUG with <runtime-debugging>on (was: Trivial issues have been neglected.)
From: Kohei Takahashi (flast_at_[hidden])
Date: 2012-10-16 15:38:30

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Hi,

(2012/10/17 0:09), Matthew Chambers wrote:
> On 10/15/2012 11:29 PM, Steven Watanabe wrote:
>> AMDG
>> 
>> On 10/15/2012 07:54 PM, Kohei Takahashi wrote:
>>> Hi all,
>>> 
>>> Can anyone handle following two issues?
>>> 
>>> <runtime-debugging>on does nothing for libstdc++... 
>>> https://svn.boost.org/trac/boost/ticket/4589
>>> 
>> 
>> This is /not/ a trivial issue.  It may be easy to do, but:
I understood about this is not trivial issue and I changed the subject.

>> a) _GLIBCXX_DEBUG was broken last time I tried it a few years
>> ago.  It won't work with all versions of gcc.
> 
> I've used it with 4.1.2 and it helped a lot to track down some 
> mysterious failures.
I don't know about old releases but recents seem to work well for me.
Indeed, expects to work well and should work with all versions of gcc
if define it by default.

>> b) Anything the changes the ABI of the compiled libraries needs
>> careful consideration and must be documented.  The libraries that
>> are built need to be ABI compatible with code that isn't
>> compiled using Boost.Build.
> 
> Is it really that important that debug builds be ABI compatible
> between disparate builds? I think it's reasonable to EXPECT trouble
> when linking a debug build to precompiled libraries. That is
> certainly the case on Windows.
<define> is not propagated feature, that means to trigger unexpected
link failure or ABI breaking. I think that using <runtime-debugging>
make safely rather than <define>.
I think it is better that provides propagated feature (as
<runtime-debugging> or another) for such purpose at least.

>> c) <runtime-debugging>on is part of <variant>debug, but I don't
>> think _GLIBCXX_DEBUG is a standard part of debug builds with
>> gcc.
> What is a "standard" debug build with gcc? Most people would
> probably say -g and -O0 but that doesn't provide any real debugging
> support.
> 
> I agree it's not trivial, but having a no-op runtime-debugging
> feature is cringe-worthy. It's as good as admitting that GCC (or
> rather, libstdc++) doesn't provide any "official" runtime debugging
> support which is unfair.
> 
> In the spirit of upcoming elections, count this as a vote for
> turning on _GLIBCXX_DEBUG. :)

Thanks,
Kohei Takahashi
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