My code using getpixel and getdc seems to have some sort of memory issue?

[river cave]

My code that i'm making to grab a pixel on the screen and gets it's color seems to have a memory issue somewhere at the line std::cout << "("; there is a segmentation fault occuring i'm new to c++ so i'm not sure why this is happening any help in debugging would be helpful, thank you. Here is my code:

#include <iostream>
#include <windows.h>

int main() {
    try {
        HDC dng = GetDC(NULL);

        if (dng) {
            COLORREF c = GetPixel(dng, 1920 / 2, 1080 / 2);

            std::cout << "(";
            // std::cout << (int)GetRValue(c) << ", ";
            // std::cout << (int)GetGValue(c) << ", ";
            // std::cout << (int)GetBValue(c) << ")";

            ReleaseDC(NULL, dng);
        } else {
            std::cout << "Null found!";
        }
    } catch (const std::exception& e) {
        std::cerr << "Exception: " << e.what() << std::endl;
    }

    return 0;
}

This is the only code in my whole project besides the .vscode settings

[quick sleet]

When your question is answered use !solved to mark the question as resolved.

Remember to ask specific questions, provide necessary details, and reduce your question to its simplest form. For tips on how to ask a good question run !howto ask.

[river cave]

I'm not sure if this is also a compiler issue I just had my friend run it and it worked perfectly fine

[spice tulip]

1. what platform are you running this on
2. what is the exact error (its really hard to get a segfault error on windows)

3. how are you compiling it?

[river cave]

1. I'm on windows 11
2. I don't get an exact error it just shows segfault exception occured
3. compiling through vscode with the task.json shown here

{
    "tasks": [
        {
            "type": "cppbuild",
            "label": "C/C++: g++.exe build active file",
            "command": "C:\\msys64\\mingw64\\bin\\g++.exe",
            "args": [
                "-fdiagnostics-color=always",
                "-g",
                "${file}",
                "-o",
                "${fileDirname}\\${fileBasenameNoExtension}.exe",
                "-lgdi32"
            ],
            "options": {
                "cwd": "${fileDirname}"
            },
            "problemMatcher": [
                "$gcc"
            ],
            "group": {
                "kind": "build",
                "isDefault": true
            },
            "presentation": {
                "echo": false,
                "reveal": "always",
                "focus": false,
                "panel": "shared",
                "showReuseMessage": true,
                "clear": true
            },
            "detail": "Task generated by Debugger."
        }
    ],
    "version": "2.0.0"
}

heres a pic of exactly what happens and the terminal down at the bottom

no errors just the segmentation fault

[spice tulip]

hmm okay well looking into GetPixel
https://learn.microsoft.com/en-us/windows/win32/api/wingdi/nf-wingdi-getpixel
it says a couple of things

The pixel must be within the boundaries of the current clipping region.

and

Not all devices support GetPixel. An application should call GetDeviceCaps to determine whether a specified device supports this function.

the first part shouldn't segfault

but perhaps the latter part does

also are you sure you definitely rebuilt

[river cave]

yeah I rebuilt a few times still didn't help

I'm gonna see that getdevicecaps fn rq to see if my pc can use the getpixel

[spice tulip]

its not pc its the device, but yes

also why do you need this specific function?

There is likely a better way to do whatever you're doing

[river cave]

I mostly just wanted to get a pixel on a screen and get the color of it for a simple color picker

at this point though I just want to diagnois why this is wrong since im new to c++ i feel like itd be helpful to learn

but if you do have a better way then yeah i'll do that afterwards

[spice tulip]

ah okay Im not actually sure on the best way to do that

If you were doing any drawing I would know better ways, but this might be the only way to do this specific thing tbf

[river cave]

i'm not really sure this was really the only fn I saw on it

Would the index passed to devicecaps be for this

[spice tulip]

honestly I don't see an obvious option that tells you if this is valid

microsoft docs can be lacking sometimes

[river cave]

yeah the docs have been very confusing on this fn

I honestly think this is something to do with my

compiler settings

[spice tulip]

I doubt it

99% of the time its not a compiler issue

[river cave]

#include <iostream>
#include <windows.h>

int main() {
        HDC dng = GetDC(NULL);
        int num = GetDeviceCaps(dng, COLORMGMTCAPS);
        if (dng) {
            std::cout << num; // Segmentation fault
            ReleaseDC(NULL, dng);
        } else {
            std::cout << "Null found!";
        }
    return 0;
}

I tried this but it was a segmentation fault

agian

mayb its an issue with getdc

[spice tulip]

try just printing anything to cout

delete the GetDC part

[river cave]

yeah i got another segmentation fault

not really sure

i just printed hello world by itself

and i rebuilt

int main() {
    std::cout << "Hello World!";
    return 0;
}

[spice tulip]

are you sure you're using the new builds?

and saved the file

[river cave]

yeah

[spice tulip]

delete the old executable just to be sure

[river cave]

i did last time

[spice tulip]

ah fair enough

[river cave]

not really sure whats wrong

I did give the actual full script to my friend

and he could run it just fine

[spice tulip]

this also segfaults?

[river cave]

yeah on the cout

[spice tulip]

okay yeah this is a config issue

[river cave]

i think ima reinstall all my compilers

cause i think my configs are all good

[spice tulip]

You're on windows right?

[river cave]

ye

im usin mingw

[spice tulip]

I would suggest visual studio over mingw

its just more ergonomic

[river cave]

i just hate visual studio to be honest with you

i know its much easier to use

but i just hate it

[spice tulip]

okay well try re-installing mingw then

[river cave]

ye

i gotta find the mingw installation manager

somewhere again

that snot a virus x.x

btw are you on windows? I think i'm just gonna use mingw through msys

should i do that or just go for the actual mingw install

[spice tulip]

I tend to prefer msvc just because it works

Ive tried mingw and when I did I didn't use msys

But its really up to you

[river cave]

ahh, i see alr

[river cave]

!solved