Using different compiler arguments for C/C++ source for shared libraries

Help/Discuss
1

I am just getting started using gradle for some C/C++ projects and I have quickly run into the need to use different compile arguments for each of the sources defined for a shared library. All I have been able to find is how to control the compiler arguments t the sope of the library, not for each individual source file. I see that the compiler arguments are housed in the CCompiler task, but there is only one of these for the entire library. Is there a way to create more than one?

2

Compiler arguments apply to the entire source set. You can’t apply different compiler arguments to different files in the source set, but you can define multiple source sets with appropriate filtering and apply different compiler arguments to each. Example:

model {
    components {
        main(NativeExecutableSpec) {
            sources {
                c.source.exclude "**/special/*.c"
                special(CSourceSet) {
                    source {
                        srcDir "src/main/c"
                        include "**/special/*.c"
                    }
                }
            }
        }
    }
}

This would exclude anything in the “special” directory from the main source set, and then include those in a separate source set. There will be a separate compile task for each source set and you can set the compiler arguments appropriately for each.

Note that the above shows creating source sets in the same directory and uses filters to differentiate them, but the conventional way to do this would be to just have separate directories and no filters.

3

OK, I get it, but can you provide a simple example of setting the compiler arguments for one of the source sets? I cannot seme to make this work. Thanks!

4

Yeah, the trick is correlating the compile task to the source set which is not straightforward. You could do it based on the name of the task or if the task source contains a known file from the source set, but neither of these feel great. Thinking about this a little more, I think the best way to handle this is to break it up across components and then have the one statically link the other. So something like:

model {
    components {
        main(NativeExecutableSpec) {
            sources {
                c {
                    source.exclude "**/special/*.c"
                    lib library: "special", linkage: "static"
                }
            }
        }
    
        special(NativeLibrarySpec) {
            sources {
                c {
                    source {
                        srcDir "src/main/c"
                        include "**/special/*.c"
                    }
                }
            }
            tasks.withType(CCompile) {
                compilerArgs = [...]
            }
        }
    }
}