[CMake] Visual Studio Warning Level

[Vladimir Prus]

Hendrik Sattler wrote:

> Am Saturday 22 November 2008 15:17:12 schrieb Vladimir Prus:
>> Michael Jackson wrote:
>> > On Nov 22, 2008, at 8:01 AM, Vladimir Prus wrote:
>> >> Bill Hoffman wrote:
>> >>> Robert Dailey wrote:
>> >>>> Hi,
>> >>>>
>> >>>> I've done some googling on how to set warning levels for visual
>> >>>> studio
>> >>>> projects generated with CMake and I can't say I really enjoy the
>> >>>> proposed solutions I've found. Literally this should be a single
>> >>>> function call like:
>> >>>>
>> >>>> cmake_warning_level( 4 )
>> >>>>
>> >>>> I expected something simple like above, but instead I found
>> >>>> solutions
>> >>>> that involved over 10 lines of code and very complex logic. This is
>> >>>> really starting to discourage me from using CMake. I won't jump
>> >>>> the gun,
>> >>>> though, and I'll assume that I just haven't found that magically
>> >>>> simple
>> >>>> solution yet. Help is greatly appreciated!
>> >>>
>> >>> CMake does not yet have a feature to flag type of mapping layer like
>> >>> that.  It is on the road map for the future.  It could be and is done
>> >>> with macros or functions in projects currently.  I am pretty sure the
>> >>> boost CMake files have macros that do this.  Anyone have a macro for
>> >>> this to post?
>> >>
>> >> Boost.Build allows you to write:
>> >>
>> >>        bjam warnings=all
>> >>
>> >> and this will lead to /W4 on msvc (and to suitable options on other
>> >> compilers)
>> >>
>> >> I don't think boost's CMake setup has this specific option, and
>> >> generally,
>> >> lacks most of advanced Boost.Build mechanisms necessary to portably
>> >> specify build properties.
>> >>
>> >> - Volodya
>> >
>> > Vladimar,
>> >     Could you please enumerate the advanced options that are missing
>> > from boost's cmake setup so that I can start working on implementing
>> > those options. (Cross Posting to Boost-CMake as that may become the
>> > more appropriate place for this )
>>
>> It might be a little bit hard to summarize several years of development,
>> and a pile of code ;-)
>>
>> The key components (relevant to the original question of setting compiler
>> options more-or-less portably) are:
>>
>> 1. Mechanism to map from portable build features to compiler options --
>> e.g. setting certain flag when the compiler is gcc and target-os=windows
>> and link=shared.
>>
>> 2. Mechanisms to refine features a specific target is built with depending
>> on requested features (e.g. on msvc, disable all warnings)
>>
>> > What are the equivalents in gcc to /w4, /w3, /w2, /w1?
>>
>> Here's the relevant code:
>>
>>         toolset.flags gcc.compile OPTIONS <warnings>off : -w ;
>>         toolset.flags gcc.compile OPTIONS <warnings>on  : -Wall ;
>>         toolset.flags gcc.compile OPTIONS <warnings>all : -Wall -pedantic ;
> 
> All warnings on gcc are: -O3 -g -W -Wall -pedantic -std=<somevalue>
> 
> 
> On gcc, when using the -pedantic option, you should also set the standards
> version that your program complies to or you will get lots of useless
> warnings/errors. To get some warnings, you need optimisation turned on and
> also use -g or you will never see them.

Optimization and debug symbols are typically different axises -- you first
decide if you're building debug or release, and if release -- whether debug
symbols are needed, and then you want all warnings from that.

> On msvc you usually want to disable some very useless warnings (like that
> funny proposal to replace "unsafe" POSIX functions with microsoft-only "safe"
> functions) and that is not handled by /w? as some other warnings may still be
> useful.

Yes, there are different opinion about that msvc warnings :-) And some gcc
warnings, too, are considered bogus by some people...

> That may still not be all warnings, depending on OS and on versions of gcc.
> 
> I don't see how this could be handled by a simply integer.

... however it proves beneficial to have relatively portable way to say what
kind of warnings you want. Fine-tuning for the compilers you use daily can be
still done with explicit options, and for compilers or compiler versions you
don't use you get a suitable approximation.

- Volodya