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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.

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,


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