How to compile with different compile options for different files in CMAKE?

Question

I have a project like this:

|--CMakeLists.txt(1)
|--File1.cpp -W -W-all
|--Folder1
    |--CMakeLists.txt(2)
    |--File2.cpp -W -W-all -fno-rtti

As you can see above, File2.cpp needs to compile with -fno-rtti whereas the other files should compile with rtti. This is happening because I'm using both clang and boost libraries in my project. I wrote CMakeLists.txt(1) like this:

SET (CMAKE_CXX_FLAGS "-std=c++11 -fexceptions -fno-rtti -D__STDC_LIMIT_MACROS -D__STDC_CONSTANT_MACROS -Wno-long-long" )

And, in CMakeLists.txt(2) I added the following:

add_definitions( -fno-rtti )

The above did not work. In fact none of the following have worked for me in CMakeLists.txt(2)

set_property(SOURCE File2.cpp APPEND_STRING PROPERTY CMAKE_CXX_FLAGS " -fno-rtti ")
set_property(SOURCE File2.cpp APPEND_STRING PROPERTY COMPILE_FLAGS " -fno-rtti ")
ADD_DEFINITIONS(CMAKE_CXX_FLAGS " -fno-rtti ")
ADD_DEFINITIONS(COMPILE_FLAGS " -fno-rtti ")
ADD_DEFINITIONS( -fno-rtti )

Am I missing anything?

How do you know it didn't work? What errors do you get? Have you tried this? — Florian
– Florian, Commented Jun 19, 2017 at 18:27
This question is similar to: Override compile flags for single files. If you believe it’s different, please edit the question, make it clear how it’s different and/or how the answers on that question are not helpful for your problem. — user202729
– user202729, Commented Oct 31 at 1:33

rocambille · Accepted Answer · 2017-09-23 06:30:26Z

12

AFAIK CMake does not allow to specify compile options per file. The best you can do is to create a target for the files you want to compile with -fno-rtti, e.g. with add_library, and add the compile options to this target.

add_definitions is meant to add preprocessor definitions. You should consider add_compile_options instead:

add_compile_options(-fno-rtti)

To avoid global pollution and make sure you add your options only to a given target, you may consider using target_compile_options:

target_compile_options(foo PUBLIC -fno-rtti)

Unrelated, but instead of manually setting flags to enable c++11 with set(CMAKE_CXX_FLAGS "-std=c++11 ..."), let cmake do a more fine grained job with compile features, or at least with standard selection:

set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

EDIT:

Looking more carefully in the documentation, you can set compile flags per source file using set_source_files_properties with COMPILE_FLAGS:

set_source_files_properties(File2.cpp PROPERTIES COMPILE_FLAGS -fno-rtti)

edited Sep 23, 2017 at 6:30

answered Jun 19, 2017 at 17:04

rocambille

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5 Comments

Florian Over a year ago

To avoid global pollution wouldn't it be better to use PRIVATE instead of PUBLIC target compile options?

Utkarsh Kumar Over a year ago

I'm accepting this answer, but the fix was actually in the CmakeLists.txt(2). I was not building (by calling add_library) for that individual file. Once I added the add_library, and linked it at top level , it was OK. Not sure if there is a way to workaround (must be) without creating a lib out of this one file. For ex. in XCODE we can specify directly which files need to compile with which options and generates a single executable. Does Cmake allow that ? If yes, what should I add in CMakeLists.txt(2) ?

rocambille Over a year ago

@UtkarshKumar I reread your question and the documention, set_source_files_properties should work for you. In your question, you used it on File1.cpp instead of File2.cpp: is that a typo?

Utkarsh Kumar Over a year ago

Thanks for correcting. I haven't tried set_source_files_properties, I think I only tried set_property. Would verify against this command and update.

Kevin Over a year ago

It looks like COMPILE_FLAGS is now deprecated, and COMPILE_OPTIONS should be used instead.

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