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Using Visual Studio Code 1.39.2 on Ubuntu 18.04. My C++ program has tasks for generating a Makefile with Cmake using the command cmake -G 'Unix Makefiles' -DCMAKE_BUILD_TYPE=Debug ... There is an equivalent Release version.

Thereafter, a make task is run which correctly builds a DEBUG and RELEASE version in ./PROJECT/build/Debug or ./PROJECT/build/Release folders.

The problem is that Visual Studio Code does not understand any Debug or _DEBUG symbols, so code like the following does not work as expected:

#ifdef _DEBUG   // or #ifdef Debug
    cout << "Debug build\n";
#else
    cout << "Release build\n";
#endif

When the application is run, only Release build is printed, never Debug build. Moreover, in the Visual Studio Code editor, the Debug build line is greyed out.

Manually defining the symbols with #define DEBUG is an option, but will require manually editing the file every time the build type is changed.

How do you get Visual Studio Code to define and understand the correct symbols based on the selected build task? Or is there some clever way to get Code to "look into" the generated CMake/make files (such as CMakeCache.txt, cmake_install.cmake, Makefile)?

AlainD
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    Possible duplicate of [How to use #ifdef \_DEBUG on Linux?](https://stackoverflow.com/questions/9034700/how-to-use-ifdef-debug-on-linux) – walnut Nov 09 '19 at 21:55
  • `cmake` is a commandline utility, which is only triggered by VS Code. Does it work as expected from the commandline? If not, you can remove every reference to VS Code from this question in order to reduce the scope a bit. – Ulrich Eckhardt Nov 09 '19 at 22:25
  • Not a duplicate. That other question is neither related to Visual Studio Code, nor CMake 3.13 (the commands mentioned are apparently obsolete), nor do they work. – AlainD Nov 09 '19 at 22:39
  • The `_DEBUG` and related symbols are typically passed to the compiler on the command line (`/D_DEBUG`). – 1201ProgramAlarm Nov 09 '19 at 22:59
  • @1201ProgramAlarm: Do you know how to get Visual Studio Code to know about the definitions. – AlainD Nov 11 '19 at 13:27

2 Answers2

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Note: This solution will resolve the issue of symbols not being understood during compilation. However, the problem of the Visual Studio editor not understanding the _DEBUG or NDEBUG symbols for presentation remains an issue.

In comments to the question, this question was suggested as a duplicate. There is some overlap, but that question refers to the Eclipse IDE and uses obsolete CMake commands. But it did gives some clues and after digging into the CMake documentation, allows the problem to be resolved with these changes to CMakeLists.txt:

Step 1 - If required, set the CMake build type explicitly

Near the top of CMakeLists.txt, add the following:

if (CMAKE_BUILD_TYPE STREQUAL "")
    # Build type is not set eg. command was "cmake .."
    message(STATUS "  Diag: Build type was unspecified, set to Release")
    set(CMAKE_BUILD_TYPE Release)
else ()
    message(STATUS "  Diag: Build type specified as '${CMAKE_BUILD_TYPE}'")
endif ()

Step 2 - Define "_DEBUG" and other symbols

After the code from step 1 add the following:

if (${CMAKE_BUILD_TYPE} STREQUAL Debug)
    set_directory_properties(PROPERTIES COMPILE_DEFINITIONS "_DEBUG")
else ()
    set_directory_properties(PROPERTIES COMPILE_DEFINITIONS "NDEBUG")
endif ()

Now call CMake in one of the following three ways from some build folder. This can either be from the command-line or as a task inside Visual Studio Code, then make the final binary:

  • cmake ..
  • cmake -G 'Unix Makefiles' -DCMAKE_BUILD_TYPE=Release ..

Release binary and Release build is displayed

  • cmake -G 'Unix Makefiles' -DCMAKE_BUILD_TYPE=Debug ..

Debug binary and Debug build is displayed

AlainD
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You can add "-D _DEBUG" at task.json file under "args": When you add this parameter, with CTL+F5, you can build in debug mode.

Pejman Mohebali
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