Using -c gives warnings

[ojwb]

After building and installing clang 3.1 with the IOC patches, I get warnings with -c:

$ clang -fcatch-undefined-ansic-behavior -O -c add.c
clang: warning: -ltrapub: 'linker' input unused when '-c' is present
clang: warning: -lm: 'linker' input unused when '-c' is present

If using -Werror, these get promoted to errors.

Without -fcatch-undefined-ansic-behavior there are no warnings, so it looks like it is adding these options implicitly. Perhaps it should only add linker options when linking?

[dtzWill]

Sorry for the delay, somehow missed this!

Yes, this happens and for the reason you mention--we aren't good about only adding those flags when they're needed. Does this break anything for you? If so, I can prioritize putting a fix together.

If building mainline clang/compiler-rt is an option for you, you might consider doing so: as of today the majority of IOC's checks are available upstream!

The primary related flags are now "-fsanitize=integer" and "-fsanitize=undefined", both imply a number of individual checks that you can also specify manually as desired. See http://clang.llvm.org/docs/UsersManual.html#codegen for more information, and don't hesitate to let me know if you have any questions or issues!

[ojwb]

Is there a preferred place to report issues rather than here?

Turning on -Werror when doing development is fairly common (because it avoids the trap of introducing a new warning by not noticing it when you first recompile the file it is in, and then the warning doesn't reappear until that file changes again). For Xapian, we turn it on automatically in a developer build, and I believe some other projects have similar arrangements.

So this means that to use the IOC clang in a developer build, I have to manually disable -Werror. It does break stuff, but there is at least a workaround.

Great to hear this is getting merged. Using the upstream clang should be an option for me - it just means I'll need to build again.