Re: [Boost-build] From where do compiler options come ?

Subject: Re: [Boost-build] From where do compiler options come ?
From: Edward Diener (eldiener_at_[hidden])
Date: 2015-09-29 22:19:05

On 9/29/2015 3:05 AM, Vladimir Prus wrote:
> On 29-Sep-15 9:57 AM, Vladimir Prus wrote:
>> On 28-Sep-15 11:25 PM, Vladimir Prus wrote:
>>> The priority order is roughly this:
>>> - default values, here  warnings=on
>>> - properties on the command line, none in your case
>>> - requirements on projects and metatargets
>>>
>>> I am surprised you still get -Wall, I'll take look tomorrow.
>>
>> Edward,
>>
>> with the patch below, when I run "b2 --debug-building", I see that
>> <warnigns>off is in build properties. With msvc, I also see /W0, which
>> is the expected warning option. Could you try exactly same patch and see
>> whether -Wall is still there?
>>
>> --- test/Jamfile
>> +++ test/Jamfile
>> @@ -15,7 +15,7 @@ project
>>     ;
>>
>>   test-suite lambda
>> -  : [ run algorithm_test.cpp ]
>> +  : [ run algorithm_test.cpp : : : <warnings>off ]
>>       [ run bind_tests_simple.cpp ]
>>       [ run bind_tests_advanced.cpp ]
>>       [ run bind_tests_simple_f_refs.cpp ]
>
> The same patch also eliminates -Wall on Ubuntu with gcc.

What I see is that I can override the -Wall default if I specify 
"warnings=off" on the command line. Also if either the jam file has 
project requirements with "<warnings>off" or individual target has the 
"<warnings>off" the -Wall default is overridden.

However evidently, as specified in the documentation for the gcc toolset 
at 
http://www.boost.org/build/doc/html/bbv2/reference/tools.html#bbv2.reference.tools.compiler.gcc, 
the end-user can not use "<warnings>off" ( or any "<warnings>" option ) 
at the toolset level. I am trying to use it for clang, not gcc, but 
there is no documentation for the clang toolset in the Boost Build docs 
so I assume the same restriction goes for clang. Is there a reason why 
general requirements could not be part of the 'using' rule aside from 
the fact that it was not designed that way ? It would surely be useful 
to specify any feature, and not just the limited features which are 
direct compiler options, in the 'using' rule. I think the end-user 
should be able to specify a general requirement for his toolset which 
overrides the default requirement. My particular need is that clang 
outputs an awful lot of detail even when warnings occur, so I would like 
to limit as an end-user the warnings for that compiler. Doing it on the 
command line is possible but it is much easier if I could do it at the 
toolset level and treat the command line generically as to the toolset ( 
which is what I currently do by invoking 'b2' from batch files ).