It would seem that enabling GCC's type conversion/truncation warnings would be a good thing for Python builds.

This would bring GCC builds in line with MSVC builds and reduce the burden on the Windows developers in fixing them.  Also, it would bring attention to those issues by the developer who writes code and would hopefully understand the truncation issues at hand.

The CFLAGS required for this are '-Wconversion -Wno-sign-conversion'.

I unfortunately do not know the autoconf foo needed to implement this suggestion, however.  Perhaps it should only be enabled for debug builds as well to eliminate excess noise for other builds.  Or at least enabled on some of the buildbots.

How many extra warnings do you get by adding these flags (e.g., just by doing 'export CFLAGS= ...' before building)?  It might be useful to see a sampling of those warnings.

The addition of these flags should be conditional on gcc's version being >= 4.3:  gcc 4.2 apparently has a different meaning for -Wconversion (to do with implicit conversions when passing function arguments), and generates crazy numbers of warnings on my OS X 10.6 machine (which comes with gcc 4.2).

Why '-Wno-sign-conversion'?  Is fixing all the places that have implicit sign conversions a reasonable goal, or are there just too many of those?

I'm getting more than thousand warnings:

$ CFLAGS="-Wconversion -Wno-sign-conversion" ./configure
$ LC_ALL=C make -s -j8 2>&1 | tee log
$ grep Wconversion log | wc -l
1163

platform: Ubuntu 12.04 x86_64
gcc: 4.6.3

> I'm getting more than thousand warnings:
>
> $ CFLAGS="-Wconversion -Wno-sign-conversion" ./configure
> $ LC_ALL=C make -s -j8 2>&1 | tee log
> $ grep Wconversion log | wc -l
> 1163

My Win64 buildbot currentlyhas 544 conversion warnings, but it seems
something has recently changed with OpenSSL thus causing over 2100
total warnings.