How to disable a false positive error in vscode?

Question

I have wrote this basic C program:

int main(int argc, char const *argv[])
{
    int n = rand();
    int a[n];
    return a[0];
}

Which is getting compiled properly in gcc. But MS C/C++ intellisense in showing error squiggles stating expression must have a constant value C/C++(28) [4, 8]. After some googling I have found out that MSVC have not implemented VLAs. But I am unable to find a way to suppress this error. Someone please help me out!

EDIT: Also, surprisingly it is not warning for implicit declaration of rand in line 3 !!!

EDIT: If possible, can someone also mention an alternative extension for C/C++.

EDIT: I am using:

• Microsoft VSCode v1.63.2 code editor
• Microsoft C/C++ Extension Pack v1.1.10 extension
• MinGW-W64 gcc v8.1.0 compiler

GCC no compilation flags are set.

C/C++ extension is configured with following:

• compilerPath: C:\Program Files\mingw-w64\mingw64\bin\gcc.exe
• cppStandard: gnu++20
• cStandard: gnu17
• intelliSenseMode: windows-gcc-x64

Answer 1

This shows as an error because it indeed is an error. When you're using the MSVC compiler it is only going to give you the results from MSVC compilation.

Now, this is actually due to the fact that you're doing the wrong thing. It seems that you want to initialize an array with a size n which is obtained from a random value. In other words, you should perform a dynamic allocation, that is, allocation of memory during runtime. Since you are using C, you must use the malloc functions for this as shown:

#include <stdlib.h>
int main(int argc, char const *argv[])
{
    int n = rand();
    int *a = malloc(n * sizeof(int));//Dynamic allocation of an array
    int val = a[0];//Garbage value
    free(a);//Deallocation / Free the memory taken by array 
    return val;
}

If want to replace MSVC with gcc, you can change the default compiler of C/C++ in VS code by changing the setting:

Change your setting

C_Cpp.default.compilerPath` : C:\MinGW\bin\g++.exe

EDIT: I mistakenly mentioned that the path should be of the bin folder. Instead, it should be of g++.exe itself. I downloaded the latest binary and confirmed it for you.

You can do this by going to the VS code preferences, searching for C_Cpp.default.compilerPath in the search bar, which would lead you to the required input box. Enter C:\mingw64\bin\gcc.exe and the compilation would replace MSVC with gcc/g++

Finally, try to avoid VLA and use dynamic allocation as it is a safer and much supported practice.