gcc, make: how to disable fail on warning?

Question

I'm trying to build gcc for use with an AVR micro controller and avr-ada, and I've hit a roadblock caused by my regular compiler being too picky about the version I needed for the AVR. I get the following warning, which in turn causes the gcc or make to report an error:

gcc -c -g -O2 -gnatpg -gnata -nostdinc -I- -I. -Iada 
  -I../../gcc/ada ../../gcc/ada/exp_ch5.adb -o ada/exp_ch5.o
exp_ch5.adb:177:16: warning: function "Has_Address_Clause" is not referenced
make[2]: *** [ada/exp_ch5.o] Error 1
make[1]: *** [all-gcc] Error 2
make: *** [all] Error 2

Is there a way to instruct gcc or make to not fail on warnings?

Answer 1

Try make -k instead of just make. That will 'continue' rather than stop.

Answer 2

It seems -Werror flag is set in Makefile. Maybe you can look for CFLAGS options in Makefile and remove the -Werror flag. The Werror flag will make all warnings into errors.

Answer 3

In general, it is not a good idea to ignore warnings from your compiler. However, if this is a portion of a larger make process there is likely a -Werror flag inserted earlier in the sequence. Start by looking for that.

After looking around, there seems to be a wealth of flags to control warnings while compiling Ada code. For instance, -gnatwF will Suppress warnings on unreferenced formals according to this guide. Possibly the switch you require can be found in the list provided there.

Answer 4

As an alternative to diving into the build system, try setting -Wno-error in CFLAGS, which you should be able to do through the environment (or at configure time, if using the GNU build system).

Answer 5

The trigger here is the -gnatpg (actually, the -gnatg): this is the "GNAT implementation mode (used for compiling GNAT units)". -gnatp means "suppress all checks".

I'm not sure of the full effect of -gnatg, though it certainly causes warnings to be treated as errors -- like -Werror -- at any rate while building the compiler itself; I think I remember seeing non-fatal warnings while building the RTS.

One possibility would be to compile just exp_ch5.adb by hand without -gnatg; the command you list was issued at gcc/, so

$ cd gcc
$ gcc -c -g -O2 -gnatp -gnata -nostdinc -I- -I. -Iada -I../../gcc/ada ../../gcc/ada/exp_ch5.adb -o ada/exp_ch5.o

Then back up one level, and 'make' again.

This is a cross-compiler, so you won't (I hope!) need to repeat this for all three stages of a full build.

Answer 6

How about putting "pragma warnings(off, "...")" into the offending parts of your code?

See http://www.adacore.com/2007/11/19/ada-gem-18/.