GCC Runtime Library Exception in gcc/config/* files?

[Jeff Law]

On 07/21/2017 12:14 PM, Georg-Johann Lay wrote:
> Sebastian Huber schrieb:
>> Hello,
>>
>> there are some files in gcc/config/* that contain the GCC Runtime
>> Library Exception
>>
>> grep -r --include='*.[ch]' 'GCC Runtime Library Exception' -l
>> gcc/config | wc
>>     186     186    5361
>>
>> and some files that don't include it
>>
>> grep -r --include='*.[ch]' 'GCC Runtime Library Exception' -l
>> gcc/config -v | wc
>>     753     753   20927
>>
>> Does it matter? What should be used for new files?
> 
> Some machine headers are needed by libgcc.  Not all information is
> available by means of built-in macros, so that compile-time decisions
> in libgcc might need the target headers.
But just because we make a compile time decision doesn't mean the tm.h
file needs to have the exception clause.  IMHO what matters is whether
or not code gets embedded.

For example, if there's a macro in a tm.h file that generates a blob of
assembly code and that assembly code is embedded into libgcc.  Then we
probably need an exception clause.

> 
> Likely, this dates back to the time when machine specific libgcc bits
> where in gcc/config/$target.
> 
> Some users of (lib)gcc which compile their (proprietary) software
> with gcc are paranoid about being infected by GPL due to using
> libgcc which uses headers without runtime library exception.
Yes, but that doesn't mean we just blindly put the exception clause on
all the target headers.

> 
> https://gcc.gnu.org/ml/gcc-help/2012-08/msg00235.html
> 
> See also
> 
> https://gcc.gnu.org/PR61152
IMHO the proper thing to do here is identify what parts potentially
introduce *code* into the library.  Those need to have the exception
clause.  Adding the exception clause to the tm.h files blindly seems
wrong to me.

jeff