I still don't get additional error messages on the trunk. I've altered
the configure.in file to include -Wstrict-overflow=5 after -Wall:

gcc -pthread -c -fno-strict-aliasing -g -Wall -Wstrict-prototypes
-Wstrict-overflow=5  -I. -IInclude -I./Include   -DPy_BUILD_CORE -o
Objects/listobject.o Objects/listobject.c

Either all problems are already solved or I'm doing something wrong here.

$ LC_ALL=C gcc-4.2 -v
Using built-in specs.
Target: i486-linux-gnu
Configured with: ../src/configure -v
--enable-languages=c,c++,fortran,objc,obj-c++,treelang --prefix=/usr
--enable-shared --with-system-zlib --libexecdir=/usr/lib
--without-included-gettext --enable-threads=posix --enable-nls
--with-gxx-include-dir=/usr/include/c++/4.2 --program-suffix=-4.2
--enable-clocale=gnu --enable-libstdcxx-debug --enable-mpfr
--enable-targets=all --enable-checking=release --build=i486-linux-gnu
--host=i486-linux-gnu --target=i486-linux-gnu
Thread model: posix
gcc version 4.2.1 (Ubuntu 4.2.1-5ubuntu4)