compiling C++ and ObjC files in same Project

Question

I don't know if this is some silly mistake from my end, or Xcode 4.2.1 is doing something, but I'm unable to compile even a simple project that has both C++ and ObjC files. I've done this in past, but somehow the compiler is treating the C++ header files as ObjC header and throwing silly errors like

Test.h

I'm able to compile if I force to compile all files as ObjectiveC++ from "Project Settings > Apple LLVM compiler 3.0 - Language > Compile Sources As". But, that is just a workaround and I don't want to fight any thing silly when the code has grown.

For files containing (or #including) both Objective-C and C++ code, have you given them the .mm file name extension? — pmdj
– pmdj, Commented Dec 22, 2011 at 18:36
There a 4 files in the project Test.h Test.cpp AppDel.h and AppDel.m. Test.* files contain pure c++ code, while AppDel.* have pure ObjectiveC code, the AppDel.m contains a '#import Test.h' — chunkyguy
– chunkyguy, Commented Dec 22, 2011 at 18:49
If AppDel.m imports Test.h, then it is not pure Objective-C code. So it has to be called AppDel.mm (or change the type manually) — Firoze Lafeer
– Firoze Lafeer, Commented Dec 22, 2011 at 18:53

Bill Burgess · Accepted Answer · 2011-12-22 18:38:01Z

3

I just did this with a project I am working on. I believe @pmjordan is right, you need to rename any files referencing the C++ code to .mm files, rather than .m.

answered Dec 22, 2011 at 18:38

Bill Burgess

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4 Comments

chunkyguy Over a year ago

but in future I'm planning to use box2d code, which contains all .cpp files, I don't think renaming is the real option

matthias Over a year ago

You can compile wholly-C++ files separately (just make sure they have the .cpp extension) from Objective-C files (.m), then use Obj-C++ files (.mm) to design the interface between box2d and your Cocoa code. They all compile down to .o files that can be linked together. The different files are just to tell the compiler what rules to follow for each compilation unit.

chunkyguy Over a year ago

Yes, thanks, renaming the .m files that import c++ code to .mm has resolved my issue :)

Loki Astari Over a year ago

Yes Just like C/C++ are different languages Obj-C/Obj-C++ are different languages. The compiler need to know which you are using.

Cliff · Accepted Answer · 2011-12-22 18:48:34Z

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In XCode 4.2 you can also change the type of individual files using the "File Type" setting in the "Identity and Type" inspector on the right pane. I would suggest looking into this if it only with particular header files that you're having trouble with. Maybe change the type from Objective C header to C++ header?

answered Dec 22, 2011 at 18:48

Cliff

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