[llvm-dev] Question about LLVM Building Error with "-DLLVM_ENABLE_DUMP" and "RelWithDebInfo"

Mon Apr 10 12:42:39 PDT 2017

> On Apr 10, 2017, at 12:37 PM, Matthias Braun <mbraun at apple.com> wrote:
> 
> The situation is not consistent. Yes there are several places where we have the #if in the headers however there are far more cases where it is not. Some points here:
> 
> - This whole LLVM_DUMP_FUNCTION/LLVM_ENABLE_DUMP is about enabling the linker to strip (or not strip) the dumping function in release (debug) builds.
> - For this it doesn't matter whether you have a declaration in the header or not, so it seems we standardized on not having it there.
> - Things are 100% consistent so we sometimes have #ifs anyway.
> - In case of templates we not only have the declaration but also an implementation in the header and need the #if there
> - A similar problem arises in cases where the dump function was declared virtual and ends up in the vtable
> - If you ask me then we shouldn't have LLVM_ENABLE_DUMP and just rely on NDEBUG to keep things simple... (We're in this strange state anyway where LLVM_ENABLE_DEBUG isn't even exposed as a cmake option).
> - Either way, putting LLVM_ENABLE_DUMP into config.h would make the status-quo more consistent.

Using the config.h instead of the NDEBUG makes it robust against client using NDEBUG differently from what LLVM was built with. This seems really better to me.

— 
Mehdi

> 
> - Matthias
> 
>> On Apr 10, 2017, at 12:17 PM, Chris Bieneman <beanz at apple.com <mailto:beanz at apple.com>> wrote:
>> 
>> Presently several of our headers have definitions like:
>> 
>> #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
>>   void dump() const;
>> #endif
>> 
>> Would it make sense to modify the build system to define LLVM_ENABLE_DUMP in config.h on debug builds?
>> 
>> Then we could wrap dump methods just based on LLVM_ENABLE_DUMP instead of two variables.
>> 
>> -Chris
>> 
>>> On Apr 10, 2017, at 1:34 PM, Robinson, Paul via llvm-dev <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote:
>>> 
>>> 
>>> 
>>>> -----Original Message-----
>>>> From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org <mailto:llvm-dev-bounces at lists.llvm.org>] On Behalf Of Mehdi
>>>> Amini via llvm-dev
>>>> Sent: Sunday, April 09, 2017 2:26 PM
>>>> To: Matthias Braun
>>>> Cc: llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>; jingu at codeplay.com <mailto:jingu at codeplay.com>
>>>> Subject: Re: [llvm-dev] Question about LLVM Building Error with "-
>>>> DLLVM_ENABLE_DUMP" and "RelWithDebInfo"
>>>> 
>>>> 
>>>>> On Apr 7, 2017, at 4:45 PM, Matthias Braun via llvm-dev <llvm-
>>>> dev at lists.llvm.org <mailto:dev at lists.llvm.org>> wrote:
>>>>> 
>>>>> I think the idea is to keep NDEBUG out of headers when possible. So I
>>>> think this should better be something like:
>>>>> 
>>>>> -#ifndef NDEBUG
>>>>>  void dumpUses(unsigned RegNo) const;
>>>>> -#endif
>>>>> 
>>>>> to be inline with various other dumpers (like MachineInstr::dump(),
>>>> Pass::dump(), …)
>>>> 
>>>> I’m fine with leaving methods there, but we need to be able to compile-out
>>>> fields in structure.
>>> 
>>> Hmmm seems to me this has come up in the past, and somebody pointed out
>>> that it prevents building a debug-mode front-end against a release-mode LLVM.
>>> (Why is that a valid use-case?  If I have an out-of-tree front end, and
>>> especially one with a different license, I might well prefer to download
>>> only LLVM releases rather than keep up-to-date with a live tree that I
>>> build myself.  IIRC we do not provide debug-mode downloads, therefore 
>>> anything that affects struct size/layout will break this use-case.)
>>> --paulr
>>> 
>>>> 
>>>> We already have ABI_BREAKING_CHECKS for instance to this end, the naming
>>>> isn’t completely in line with LLVM_ENABLE_DUMP but could be unified.
>>>> 
>>>> —
>>>> Mehdi
>>>> 
>>>> 
>>>>> 
>>>>> If that works for you please submit a patch to phabricator as described
>>>> in http://llvm.org/docs/DeveloperPolicy.html#making-and-submitting-a-patch <http://llvm.org/docs/DeveloperPolicy.html#making-and-submitting-a-patch>
>>>>> 
>>>>> - Matthias
>>>>> 
>>>>>> On Apr 6, 2017, at 7:38 AM, jingu at codeplay.com <mailto:jingu at codeplay.com> via llvm-dev <llvm-
>>>> dev at lists.llvm.org <mailto:dev at lists.llvm.org>> wrote:
>>>>>> 
>>>>>> Hi All,
>>>>>> 
>>>>>> I have tried to build llvm tip as following:
>>>>>> 
>>>>>> cmake -DCMAKE_CXX_FLAGS:STRING="-DLLVM_ENABLE_DUMP" -
>>>> DCMAKE_BUILD_TYPE=RelWithDebInfo ../llvm
>>>>>> 
>>>>>> After running 'make', I have got error messages like below.
>>>>>> 
>>>>>> llvm/lib/CodeGen/MachineRegisterInfo.cpp:462:67: error: no ‘void
>>>> llvm::MachineRegisterInfo::dumpUses(unsigned int) const’ member function
>>>> declared in class ‘llvm::MachineRegisterInfo’
>>>>>> 
>>>>>> llvm/lib/CodeGen/MachineScheduler.cpp:2331:57: error: no ‘void
>>>> llvm::SchedBoundary::dumpScheduledState()’ member function declared in
>>>> class ‘llvm::SchedBoundary’
>>>>>> 
>>>>>> ...
>>>>>> 
>>>>>> It seems the "defined(LLVM_ENABLE_DUMP)" is needed on several
>>>> locations. How do you think about it? I have attached the diff file about
>>>> the locations for reference.  If I missed something, please let me know.
>>>>>> 
>>>>>> Thanks,
>>>>>> 
>>>>>> JinGu Kang
>>>>>> 
>>>>>> <dump.diff>_______________________________________________
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>>>>>> llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>
>>>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev <http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev>
>>>>> 
>>>>> _______________________________________________
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>>>> 
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