Add ".c++" as a known C++ file extension

[dsvi]

added *.c++ extension

[ratzlaff]

Is this a common extension?

[samsinsane]

This was requested in #612, however, I'm fairly certain that this change won't work for gmake2 based on this snippet:

premake-core/modules/gmake2/gmake2_cpp.lua

Lines 59 to 63 in ed483dd

	rule 'cpp'
	fileExtension { ".cc", ".cpp", ".cxx", ".mm" }
	buildoutputs { "$(OBJDIR)/%{premake.modules.gmake2.cpp.makeUnique(cfg, file.objname)}.o" }
	buildmessage '$(notdir $<)'
	buildcommands {'$(CXX) %{premake.modules.gmake2.cpp.fileFlags(cfg, file)} $(FORCE_INCLUDE) -o "$@" -MF "$(@:%.o=%.d)" -c "$<"'}

[dsvi]

Is this a common extension?

Relatively. qmake/qtcreator recongnizes it as C++ file.

I'm fairly certain that this change won't work for gmake2 based on this snippet:

Nothing will, since gmake2 does not rely on the path. functions. gmake works fine with this change.

[samsinsane]

Relatively. qmake/qtcreator recongnizes it as C++ file.

Do you have any examples of what uses this extension? I'm kind of curious about where this extension comes from, things seem to support it but nobody seems to use it. I find this really weird.

Nothing will, since gmake2 does not rely on the path. functions. gmake works fine with this change.

I didn't go any deeper than the rule definition, but I kind of assumed the path. functions weren't called further down. FWIW, this change will need to work in gmake2 before we can merge it.

[dsvi]

Do you have any examples of what uses this extension?

https://www.google.com/search?q=.c%2B%2B+file+extension
gcc toolset recognizes it as well
https://gcc.gnu.org/onlinedocs/gcc/Overall-Options.html
Anyway, it doesn't hurt to add, does it?

FWIW, this change will need to work in gmake2 before we can merge it.

I believe the best way to achieve it, is to redesign gmake2 to rely on the detection functions from path., like gmake does.
This change as it is doesn't break anything in gmake2

[ratzlaff]

Can you implement any new tests with the gmake and gmake2 generators for this extension?

[dsvi]

Hmm...

[tdesveauxPKFX]

Do you have any examples of what uses this extension?

https://www.google.com/search?q=.c%2B%2B+file+extension
gcc toolset recognizes it as well
https://gcc.gnu.org/onlinedocs/gcc/Overall-Options.html
Anyway, it doesn't hurt to add, does it?

FWIW, this change will need to work in gmake2 before we can merge it.

I believe the best way to achieve it, is to redesign gmake2 to rely on the detection functions from path., like gmake does.
This change as it is doesn't break anything in gmake2

Indeed, it does not hurt and recognizing the same extensions as GCC looks fine to me.
However, I agree with @samsinsane here. The gmake generator will be deprecated in favor of gmake2 in the future so we'd need to have this works for gmake2 to merge.
From a quick look, I think you only need to make changes https://github.com/premake/premake-core/blob/master/modules/gmake2/gmake2_cpp.lua#L60 and https://github.com/premake/premake-core/blob/master/modules/gmake2/gmake2_cpp.lua#L102-L113.

And as @ratzlaff mentioned, a simple unit test that confirm that the correct rule is applied would be great in case a future change break this. There don't seem to be one at the moment but it would have it's place in *_file_rules.lua file test.

[starkos]

I'm approving this one. The Gmake2 issues should be addressed on their own.