Hello,
I’m getting started with C++23 modules and trying to use them in a personal project.
The plan is to create an executable for the entire project, which would contain the output of all unit tests.
Each source cpp file has an implementation and a unit test. The module cppm file exports unit tests from all source files in the same directory.
These exported unit tests are then called in main.cpp.
The project layout is:
.
|---- CMakeLists.txt
|---- src
| |---- foo
| |---- add.cpp
| |---- subtract.cpp
| |---- foo.cppm
|
|---- main.cpp
As I make more progress on this project, there will be other directories in src/ similar to foo/.
Below are the file contents (collapsing to improve overview)
`src/foo/add.cpp` (`subtract.cpp` is similar)
import std;
#include <cassert>
class AddNumbers {
public:
int add(int a, int b) {
return a + b;
}
};
void testAddNumbers() {
AddNumbers solution;
int result = solution.add(2, 2);
int expected = 4;
assert(result == expected); // Assert the result
}
`src/foo/foo.cppm`
export module foo;
export void testAddNumbers();
export void testSubtractNumbers();
`src/main.cpp`
import foo;
int main() {
testAddNumbers();
testSubtractNumbers();
return 0;
}
`CMakeLists.txt`
cmake_minimum_required(VERSION 3.31)
set(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD "0e5b6991-d74f-4b3d-a41c-cf096e0b2508")
set(CMAKE_CXX_MODULE_STD ON)
set(CXXFLAGS "-Wall -Werror -O2 -Wno-error=sign-compare -Wno-pre-c++20-compat -std=c++23 -stdlib=libc++")
set(CMAKE_CXX_FLAGS "${CXXFLAGS}")
set(CMAKE_CXX_COMPILER clang++)
project(testmod VERSION 1.0 LANGUAGES CXX)
set(CMAKE_CXX_STANDARD 23)
set(CMAKE_CXX_STANDARD_REQUIRED YES)
set(CMAKE_CXX_EXTENSIONS ON)
add_executable(testmod)
target_sources(testmod
PUBLIC
src/main.cpp
)
target_sources(testmod
PUBLIC
FILE_SET testmods TYPE CXX_MODULES
BASE_DIRS
${PROJECT_SOURCE_DIR}
FILES
src/foo/foo.cppm
)
I’m compiling and building this project like:
cmake -G Ninja -S . -B build
ninja -C build
and on the second command I’m getting an error:
main.cpp:(.text+0x2): undefined reference to `testAddNumbers@foo()'
main.cpp:(.text+0x7): undefined reference to `testSubtractNumbers@foo()'
How can get the project to work correctly ?