mkj / yocto-y2038

64-bit time_t compile warnings

Differential builds for 64-bit time_t

gcc and clang are able to flag truncated conversions for 64-bit time_t with -Wconversion, but it's pretty noisy. Comparing that against a 32-bit time_t build, however, gives a pretty clean list of code that needs attention.

Yocto makes it fairly easy to apply flags to all packages. See conf/local.conf. Some packages set -Werror by default, so workspace workarounds are used from devtool modify.

Building

This git repo is an OpenBMC build directory. Set up the build, pointing at this checkout:

bash
umask 022
cd ~/src/openbmc
. setup evb-ast2600 ~/path/to/yocto-y2038

Build once with 32-bit, then copy the log files out:

nice bitbake core-image-full-cmdline # or another target
# TODO perhaps a better way to do includes
(cd tmp/work;  rsync -a armv7ahf-vfpv4d16-openbmc-linux-gnueabi/ ../../log1-32/ --include '*/*/temp/**' --include '/*' --include '/*/*' --include '/*/*' --include '/*/*/temp' --exclude '*')

Edit conf/local.conf and enable the 64-bit TARGET_CPPFLAGS. Clean source and build again 64-bit:

rm -rf tmp/work/armv7ahf-vfpv4d16-openbmc-linux-gnueabi/
rm -rf tmp/stamps/armv7ahf-vfpv4d16-openbmc-linux-gnueabi/
nice bitbake core-image-full-cmdline
(cd tmp/work;  rsync -a armv7ahf-vfpv4d16-openbmc-linux-gnueabi/ ../../log1-64/ --include '*/*/temp/**' --include '/*' --include '/*/*' --include '/*/*' --include '/*/*/temp' --exclude '*')

Now the logs can be compared:

./difflog.sh

To produce logs such as diff1/busybox.diff.

Some are false positives, but others seem like real problems, come the year 2038.

Source

I've been working with OpenBMC (a Yocto downstream), so that's what I tested. This uses OpenBMC source tree https://github.com/openbmc/openbmc/

Tested with rev f35e6b7ecc6b5c5fdb561643831082226c586b6e