[Mesa-dev] [PATCH] configure.ac: Drop LLVM compiler flags more radically

[Michel Dänzer]

On 17/02/17 06:01 PM, Eero Tamminen wrote:
> Hi,
> 
> On 10.02.2017 02:59, Michel Dänzer wrote:
>> On 09/02/17 10:50 PM, Emil Velikov wrote:
>>> On 9 February 2017 at 08:07, Michel Dänzer <michel at daenzer.net> wrote:
>>>> From: Michel Dänzer <michel.daenzer at amd.com>
>>>>
>>>> Drop all -m*, -W*, -O*, -g* and -f* flags, with the exception of
>>>> -fno-rtti, which must be used if it's part of the llvm-config
>>>> --cxxflags
>>>> output. We don't want LLVM to dictate the flags we use, and it can even
>>>> cause build failures, e.g. if LLVM and Mesa are built with different
>>>> compilers.
> 
> Out of curiosity, where this stuff is applied?
> 
> (If you're removing all of them, result is hard to debug, non-optimized
> binary...)
> 
> 
>>> Yes, please !
>>> Reviewed-by: Emil Velikov <emil.velikov at collabora.com>
>>
>>
>>> Out of curiosity:
>>> Are you speaking of personal experience ? What was stored in the
>>> c/cpp/cxx flags that triggered build failure ?
>>
>> Building LLVM with clang 4.0 resulted in llvm-config --cxxflags
>> containing -Wstring-conversion and -fcolor-diagnostics, which aren't
>> supported by gcc 6.3.
> 
> There are generic flags that have been supported by few decades, which
> are not going to change, like -O[1-3], -Wall, -g.  Only the specific
> optimization & warning flags are something that differ between compiler
> versions (as new ones get added).

strip_unwanted_llvm_flags() only affects LLVM_CXXFLAGS, so this change
doesn't remove any compiler flags used by Mesa itself, it just prevents
llvm-config from unnecessarily adding potentially harmful compiler flags
when compiling some LLVM related Mesa code.


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer