Failure to detect gcc when gcc is compiled with --with-gcc-major-version-only

[barcharcraz]

Opensuse has been shipping gccs that output just the major number for gcc -dumpversion for many years. In gcc7 there is a switch --with-gcc-major-version-only that triggers this behavior (and suse's gcc7 packages use it). Because of the regex used on line 28 of detect.py conan fails to detect gcc in these cases.

[memsharded]

Sorry didn't get the proper solution. How should gcc --version be invoked to get the minor too? The minor is also needed.

In any case, not a critical issue, if detect fails to detect the default gcc, it can be easily configured editing conan.conf

[memsharded]

Hi @barcharcraz, we could include this for next release, but I have been googling for a solution, and still not clear. Would it work if we did gcc --version and parse the output, instead of gcc -dumpversion?

[SSE4]

@memsharded I use the following code in my scripts to detect GCC version

COMPILER_MAJOR=$(touch test.c && gcc -E -dM test.c  | grep -o '__GNUC__ [[:digit:]]' | cut -d' ' -f2)
COMPILER_MINOR=$(touch test.c && gcc -E -dM test.c  | grep -o '__GNUC_MINOR__ [[:digit:]]' | cut -d' ' -f2)

and for clang

COMPILER_MAJOR=$(touch test.c && clang -E -dM test.c  | grep -o '__clang_major__ [[:digit:]]' | cut -d' ' -f2)
COMPILER_MINOR=$(touch test.c && clang -E -dM test.c  | grep -o '__clang_minor__ [[:digit:]]' | cut -d' ' -f2)

basically idea is to use compiler version macro rather parsing --version output which may be hard to parse in reliable manner.
do you think if it makes sense to add something like that to conan detection?

[memsharded]

Sorry for leaving this so long unresolved.
@SSE4 I think implementing that in conan codebase is too much, so far doesn't seem worth to deserve the effort.
@barcharcraz The regex has improved, now able to use only the major (and #2084 introduces support for major-only gcc setting for 5, 6, 7.