CMake: compile a program twice in a row - compilation

Question

To be able to do many automatic optimizations, I want to be able to compile my program using the flag -fprofile-generate first, then run it to generate the profile and then re-compile the program with -fprofile-use instead.
This means I want to compile my program twice in a row, with two different CMAKE_CXX_FLAGS each time.
How can I do that using CMake?

Answer 1

You can build something and then run it and then build something else after execution by making use of customer targets and the "add_dependencies" command. For your gcov case you might do something like:
profile.cxx
#include <iostream>
int main(void) {
std::cout << "Hello from Generating Profile run" << std::endl;
return 0;
}
CMakeLists.txt
cmake_minimum_required(VERSION 3.1 FATAL_ERROR)
project(profileExample C CXX)
# compile initial program
add_executable(profileGenerate profile.cxx)
set_target_properties(profileGenerate PROPERTIES COMPILE_FLAGS "-fprofile-
generate")
target_link_libraries(profileGenerate gcov)
add_executable(profileUse profile.cxx)
set_target_properties(profileUse PROPERTIES COMPILE_FLAGS "-fprofile-use")
target_link_libraries(profileUse gcov)
# custom target to run program
add_custom_target(profileGenerate_run
COMMAND profileGenerate
WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}
COMMENT "run Profile Generate"
SOURCES profile.cxx
)
#create depency for profileUse on profileGenerate_run
add_dependencies(profileUse profileGenerate_run)
Output showing build -> run -> build