How to compile a single source file from list of sources set in a static library

Usage
1

Let’s say I have the following CMakeLists.txt

cmake_minimum_required(VERSION 3.22.0)

project(TallyWorld DESCRIPTION “” LANGUAGES CXX)

add_library(LibraryA STATIC
“POC/file1.cpp”
“POC/file2.cpp”
“POC/file3.cpp” )

Now to build LibraryA target I can use below command to build
cmake --build --preset= --target Library1

What I am looking a similar way to build file1.cpp,file2.cpp,etc. Something like below
cmake --build --preset= --target file1

Any help would be greatly appreciated.

Regards,
Mohsin Siddiqui

2

AFAIK CMake isn’t meant to do that. Build systems generally care about build targets (like a library or executable), not so much individual files.

If you really, really need to do that, you could always make a single library (e.g. object library) per cpp file, although 1) I’m not sure what build speed results you would get if you were to do that on a large project, 2) if two files anywhere in your project have the same name, even inside different libraries, you could easily fall into a case where you have two targets with the same name, and then CMake will complain, and 3) you will need to repeat target-specific properties like target_compile_features() for each of these libraries, which essentially means you’ll need a function to set them, which in turn will quickly make your CMake code hard to read.

# Untested, fix issues if any!
add_library(file1-lib OBJECT file1.cpp)
setup_tally_world_lib(file1-lib)
# ...
add_library(fileN-lib OBJECT fileN.cpp)
setup_tally_world_lib(fileN-lib)

add_library(tally-world-lib)
target_link_libraries(tally-world-lib
  PUBLIC
    file1-lib
    file2-lib
    # ...
    fileN-lib)

You could then run the appropriate target using the --target CLI option. As a final note, I remember reading somewhere in CMake’s doc that (for XCode only I think?) you can’t have a library with no sources as tally-world-lib does above.

Personally this seems like way too much badness for something you probably don’t need!

3

The makefile generators generate make targets for individual source files. For example, this:

add_executable(App src1.cpp src2.cpp)

will allow you to run any of the following commands:

> make src1.o
> make src2.o
> make App

Note that these targets are only generated in the makefile for the directory which defines the actual library/executable, not in any parent directory makefiles. So if your target is in an add_subdirectory(), you have to cd into the corresponding binary directory to have access to the *.o make targets. You can run make help in a directory to see the list of make targets available there; the *.o targets will be there if they’re present.

I don’t know whether any other generators offer similar functionality.

4

Yeah… This is where I also reached but agree it seems to much of complexing build system. Let me express exact reasoning why we want to do this way and may be I can get some better way to handle the same. So we are using Visual Studio 2022 as an IDE and what we want that opened cpp/kotlin/swift source, on right click I can give a option to compile a single file so that I dont have to compile whole library to see if my changes does not have any syntax error.

Please let me know if you have any idea to handle above .

5

No, its only there with Makefile and Ninja. XCode and Visual Studio Generator lacks it