C++ compiler optimisations (MSYS2 MinGW-64 bit GCC compiler used with VSCode)

Question

I'm trying to apply the different optimisation levels (-O0, -O1, -O2, -O3 and so on) to the compilation and execution of a .cpp file.

However, I can't figure out the exact syntax I need to use and where to write the instructions (i.e. in which terminal, the VSCode terminal or the MinGW terminal)?

Any help would be much appreciated.

tasks.json:

{
    "tasks": [
        {
            "type": "cppbuild",
            "label": "C/C++: g++.exe build active file",
            "command": "C:\\msys64\\mingw64\\bin\\g++.exe",
            "args": [
                "-g",
                "${file}",
                "-o",
                "${fileDirname}\\${fileBasenameNoExtension}.exe"
            ],
            "options": {
                "cwd": "${fileDirname}"
            },
            "problemMatcher": [
                "$gcc"
            ],
            "group": {
                "kind": "build",
                "isDefault": true
            },
            "detail": "Task generated by Debugger."
        },
        {
            "type": "cppbuild",
            "label": "C/C++: cpp.exe build active file",
            "command": "C:\\msys64\\mingw64\\bin\\cpp.exe",
            "args": [
                "-g",
                "${file}",
                "-o",
                "${fileDirname}\\${fileBasenameNoExtension}.exe"
            ],
            "options": {
                "cwd": "${fileDirname}"
            },
            "problemMatcher": [
                "$gcc"
            ],
            "group": "build",
            "detail": "compiler: C:\\msys64\\mingw64\\bin\\cpp.exe"
        }
    ],
    "version": "2.0.0"
}

You should have some file like `tasks.json`. Do you have it? — RoQuOTriX, Sep 22 '21 at 11:57
Can you copy the input of the file in the question? There should be some args field where you can put the arguments for the g++ compiler — RoQuOTriX, Sep 22 '21 at 12:03
@RoQuOTriX I have added the contents of task.json to the question. — V. Jain, Sep 22 '21 at 12:05

score 1 · Accepted Answer · answered Sep 22 '21 at 12:19

1

In this field:

        "args": [
            "-g",
            "${file}",
            "-o",
            "${fileDirname}\\${fileBasenameNoExtension}.exe"
        ],

add the optimization option:

        "args": [
            "-g",
            "${file}",
            "-o",
            "${fileDirname}\\${fileBasenameNoExtension}.exe",
            "-O2"
        ],

Consider that you have two tasks (I am not sure why you have the second one) and you need to set it in the correct task. If I were you I would remove the unused one and instead create a task for debug and release build: Release build in Visual Studio Code

Be careful that this is about c# and cannot be copy pasted!

answered Sep 22 '21 at 12:19

RoQuOTriX

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Thanks for your reply. I'm not sure myself why there are two tasks. Do you know how I identify the unused one? – V. Jain Sep 22 '21 at 12:21
Try to remove one and look if your program is compiling and running. If yes, then this was the unused one. If it is not working anymore, put it back and remove the other one. – RoQuOTriX Sep 22 '21 at 12:22
Ah I see I removed the second one and the build still finished successfully. Thanks for all your help! – V. Jain Sep 22 '21 at 12:24

C++ compiler optimisations (MSYS2 MinGW-64 bit GCC compiler used with VSCode)

1 Answers1