GDB not finding header, while debugging

This is what I'm trying to run:

#include "TVk-core.h"

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

"TVk-core.h" is a header from a lib I'm working on, which I included in CMakeLists.txt. "iostream" is also included in "TVk-core.h". I use g++ and compiles and runs fine. But when I try to put a breakpoint at

std::cout<<"Hello World!"<<std::endl;

and try to debug, it doesn't work, complaining about an internal error:

Execute debugger commands using "-exec <command>", for example "-exec info registers" will list registers in use (when GDB is the debugger)
/build/gdb-wIRHdd/gdb-12.0.90/gdb/value.c:1731: internal-error: value_copy: Assertion `arg->contents != nullptr' failed.
A problem internal to GDB has been detected,
further debugging may prove unreliable.
Quit this debugging session? (y or n) [answered Y; input not from terminal]
/build/gdb-wIRHdd/gdb-12.0.90/gdb/value.c:1731: internal-error: value_copy: Assertion `arg->contents != nullptr' failed.
A problem internal to GDB has been detected,
further debugging may prove unreliable.
Create a core file of GDB? (y or n) [answered Y; input not from terminal]
ERROR: GDB exited unexpectedly. Debugging will now abort.
The program '/media/luh0/PARA/Projects/Thesis-Vk/build/tests/test1' has exited with code -1 (0xffffffff).

and just aborts. I figured, maybe it is, because of the header, which turns out to be correct. If I just include "iostream" the error doesn't occur. How do I fix this?

I run Linux Mint 21 x64 on an AMD processor. I use VS Code, with the C/C++ and CMake addons. I set up a launch.json, with these contents:

{
    // Use IntelliSense to learn about possible attributes.
    // Hover to view descriptions of existing attributes.
    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
    "version": "0.2.0",
    "configurations": [
        {
            "name": "(gdb) Launch",
            "type": "cppdbg",
            "request": "launch",
            "program": "${workspaceFolder}/build/tests/test1",
            "args": [],
            "stopAtEntry": false,
            "cwd": "${fileDirname}",
            "environment": [],
            "externalConsole": false,
            "MIMode": "gdb",
            "setupCommands": [
                {
                    "description": "Enable pretty-printing for gdb",
                    "text": "-enable-pretty-printing",
                    "ignoreFailures": true
                },
                {
                    "description":  "Set Disassembly Flavor to Intel",
                    "text": "-gdb-set disassembly-flavor intel",
                    "ignoreFailures": true
                }
            ]
        }
    ]
}

I am a complete noob with gdb and never before used it, so I really don't know, if my settings even make sense. There are my C/C++ configs, idk if they make a difference, but there you go:

{
    "configurations": [
        {
            "name": "Mint64",
            "includePath": [
                "${workspaceFolder}/src/**"
            ],
            "defines": [
                "_DEBUG",
                "UNICODE",
                "_UNICODE"
            ],
            "compilerPath": "/usr/bin/cmake",
            "intelliSenseMode": "linux-gcc-x64",
            "cStandard": "gnu17",
            "cppStandard": "gnu++17"
        },
        {
            "name": "Ubuntu64",
            "includePath": [
                "${workspaceFolder}/src/**",
                "${workspaceFolder}/dependencies/*/**"
            ],
            "defines": [
                "_DEBUG",
                "UNICODE",
                "_UNICODE"
            ],
            "compilerPath": "/bin/g++",
            "cStandard": "c17",
            "cppStandard": "c++20",
            "intelliSenseMode": "linux-gcc-x64"
        }
    ],
    "version": 4
}