[boost] Section on suppressing gcc warnings complete in boost warning guidelines

Subject: [boost] Section on suppressing gcc warnings complete in boost warning guidelines
From: Patrick Horgan (phorgan1_at_[hidden])
Date: 2011-01-14 17:39:47

I added a section to the boost warnings guidelines page about 
suppressing warnings with GCC.  I think it's pretty good bringing 
together information I got on the gcc-help list, from reading the source 
and from browsing through the documentation for various releases of 
GCC.  If anyone wants to check it for correctness and/or style I would 
be very appreciative.  I would in particular like to thank Jonathan 
Wakely for his willingness to help and for the great help he gave me on 
the gcc-help list.

https://svn.boost.org/trac/boost/wiki/Guidelines/WarningsGuidelines

If you scroll to the bottom directly you'll see the end of the section 
on suppressing GCC warnings.  I moved it after the sections on turning 
on warnings and on how to deal with some common warnings to reflect the 
viewpoint of the document that suppressing should be the last resort.

I have some improvements to make to the section on strict aliasing to 
reflect the better work I did in my white paper on the subject, and I 
know the common warnings section needs information on more common 
warnings.  The way I picked the ones that are in there originally was by 
turning on warnings for an earlier version of boost, saving the output 
of building the whole tree, then checking to see what the most common 
warnings were that indicated real bugs.  That was without running tests 
or any program that used boost.  Just building boost.

It's been a long time and much good work has been done in the tree to 
get rid of those, so I should take a look at that again by turning on 
the -Wsystem-headers -Wall -Wextra and maybe -Wpedantic and seeing what 
warnings pop up in boost code that indicate real problems again.  
Wouldn't it be great if there were none?

The most painful one is -Wsystem-headers which tells GCC to report 
warnings even in files considered system files, but since many of the 
boost files include the #pragma GCC system_file it will be necessary to 
see the warnings.  Unfortunately, that means that I'll see warnings from 
real system files as well.  In boost there are 21 headers that include 
the pragma, 15 of them in boost/exception.  It's possible that they all 
really have spurious warnings you can't code around.  Those certainly 
exist.  I hope they're documented as to why they use the pragma to save 
me time looking at them.  Perhaps I'll find real bugs in them.  Probably 
not though.

Thank you,

Patrick