Fails to compile without any optimizations (aka -O0)

[kakra]

While testing some compile issues in Gentoo for v0.6.1, I found that bees won't compile with -O0 even in current master:

$ make clean && make LANG="C" CFLAGS="-O0" CXXFLAGS="-O0"

...

In file included from extentwalker.cc:6:
../include/crucible/limits.h: In instantiation of 'To crucible::ranged_cast(From) [with To = long unsigned int; From = long int]':
extentwalker.cc:483:44:   required from here
../include/crucible/limits.h:24:35: error: comparison of integer expressions of different signedness: 'long int' and 'long unsigned int' [-Werror=sign-compare]
   24 |   if (numeric_limits<From>::max() > numeric_limits<To>::max() && numeric_limits<From>::max() < numeric_limits<To>::max()) {
      |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
../include/crucible/limits.h:24:94: error: comparison of integer expressions of different signedness: 'long int' and 'long unsigned int' [-Werror=sign-compare]
   24 |   if (numeric_limits<From>::max() > numeric_limits<To>::max() && numeric_limits<From>::max() < numeric_limits<To>::max()) {
      |                                                                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
../include/crucible/limits.h:29:35: error: comparison of integer expressions of different signedness: 'long int' and 'long unsigned int' [-Werror=sign-compare]
   29 |   if (numeric_limits<From>::max() > numeric_limits<To>::max() && f > static_cast<From>(numeric_limits<To>::max())) {
      |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
../include/crucible/limits.h: In instantiation of 'To crucible::ranged_cast(From) [with To = long int; From = long long unsigned int]':
extentwalker.cc:529:90:   required from here
../include/crucible/limits.h:24:35: error: comparison of integer expressions of different signedness: 'long long unsigned int' and 'long int' [-Werror=sign-compare]
   24 |   if (numeric_limits<From>::max() > numeric_limits<To>::max() && numeric_limits<From>::max() < numeric_limits<To>::max()) {
      |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
../include/crucible/limits.h:24:94: error: comparison of integer expressions of different signedness: 'long long unsigned int' and 'long int' [-Werror=sign-compare]
   24 |   if (numeric_limits<From>::max() > numeric_limits<To>::max() && numeric_limits<From>::max() < numeric_limits<To>::max()) {
      |                                                                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
../include/crucible/limits.h:29:35: error: comparison of integer expressions of different signedness: 'long long unsigned int' and 'long int' [-Werror=sign-compare]
   29 |   if (numeric_limits<From>::max() > numeric_limits<To>::max() && f > static_cast<From>(numeric_limits<To>::max())) {
      |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1plus: all warnings being treated as errors
make[1]: *** [Makefile:48: extentwalker.o] Error 1
make[1]: Leaving directory '/home/kakra/devel/git/src/github.com/Zygo/bees/lib'

[kakra]

Actually, I don't see why that is because -Werror shouldn't depend on the optimization level. It's probably one of the optimization flags that will be enabled at -O1 (it working from level 1 up) but I wasn't able to pin-point which it is (despite comparing gcc -Q --help=optimizers -O.... Maybe it's one of the machine flags. I don't know.

Bees should maybe add the missing gcc flag to successfully compile even without optimizers enabled.

[Zygo]

Optimization eliminates unused code branches entirely, so GCC never gets to warn about their behavior. No warning, no error either.

That expression is trying to determine whether it's doing a signed-unsigned comparison when comparing values of the parameter types, and expects the overflow behavior that the warning is about. There's probably a better way to do that, but for now -Wno-error=sign-compare will get the code building.