Setting optimization settings in visual studio through cmake

Question

When I create a project for visual studio (2015) by using a cmake file, the optimization level is set to O2 by default in release mode.

I am unable to find a way to change this to other values within a cmake file. Additionaly, I would also need a program database (.pdb) to be build.

I tried:

SET(CMAKE_CXX_FLAGS "-O0")
SET(CMAKE_C_FLAGS "-O0")

and

SET(CMAKE_CXX_FLAGS_RELEASE "-O0")
SET(CMAKE_C_FLAGS_RELEASE "-O0")

as proposed here:

https://unix.stackexchange.com/questions/187455/how-to-compile-without-optimizations-o0-using-cmake

without the success. Anybody knows the right way?

Answer 1

I use this code:

string(REPLACE "-O2" "-O0" CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE}")
string(REPLACE "-O2" "-O0" CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE}")

Answer 2

Updating CMAKE_CXX_FLAGS_RELEASE and friends did not work for me. What did was:

target_compile_options(${target_name} PRIVATE "/Zi")   
target_compile_options(${target_name} PRIVATE "/Ob0")   
target_compile_options(${target_name} PRIVATE "/Od")   
target_compile_options(${target_name} PRIVATE "/RTC1")   

message(STATUS "updating options for target: ${target_name}")

It seems like cmake 3.x and up has it s.t. if we add a compile option that conflicts with a previous option, the newer option will take precedence.

Answer 3

Following the Antonio's answer the solution for me was:

First change the optimization setting:
string(REPLACE "/O2" "/Od" CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE}")

Than add a flag that creates program database file:
string(CONCAT CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE}" " /Zi")

This also works but clears everything that was set to CMAKE_CXX_FLAGS_RELEASE before the call.

SET(CMAKE_CXX_FLAGS_RELEASE "/Od /Zi")

Answer 4

For Windows MSVC, I'm using this flag: -DCMAKE_CXX_FLAGS="/Od". Looks like this:

cmake src\ -DCMAKE_CXX_FLAGS="/Od"