Can I build gcc so -Wall option is always on ?

[Andi Hellmund]

Hey David,

On Thu, 24 Dec 2009, Dr. David Kirkby wrote:
> I'm helping on the Sage maths project
>
> http://www.sagemath.org/
>
> where there are a large number of packages built, most of which ignore 
> CFLAGS. (Quite a few ignore CC and CXX too!) I'd like to display all the 
> warnings, but its hard when people overwrite CFLAGS.
>
> Is there a way I can build gcc such that effectively "-Wall" is enabled all 
> the time?
> If not, could anyone point me to where in the source code I might be able to 
> hack it, to build a version which displays all the warnings?

I doubt that you can configure gcc to enable all warnings by default, but 
I'm not 100% sure, but you could possibly use one of the following 
possiblities to hack it into gcc:

1) For C/C++ code, the function 'c_common_handle_option' sets all the 
single warnings covered/enabled by -Wall. For gcc-4.4.1, it's 
c-opts.c:378. So, to always enable -Wall, you could call 
c_common_handle_option (via the language hooks) in 
decode_options after parsing of the command-line parameters is finished. I 
didn't test it, but you should get the effect of -Wall by calling 
c_common_handle_option(OPT_Wall, NULL, true);

2) As an alternative, you could change the gcc driver to always pass -Wall 
to the compiler (cc1,cc1plus). For this, please check,

gcc.c:827 --> cc1_options

If I see it correctly, this should then work for C/C++ compilations.

I hope that is what you're searching for ...

Happy X-Mas,

- Andi -