(C) VLA recognized as a bug in v1.8.0-insiders2

[patrykkozuch]

Bug type: Language Service - Intellisens recognizes VLA as a bug

Describe the bug

• OS and Version: Windows 11
• VS Code Version: 1.63.2
• C/C++ Extension Version: v1.8.0-insiders2

Steps to reproduce
After creating VLA in C (C89 standard) IntelliSense marks every use of Variable Length Arrays as an error.

Code sample and logs

#include <stdlib.h>
#include <stdio.h>

void bubblesort(int k, int n, char p1[][k]); /* Line marked as "a parameter is not allowed" */

int main(void)
{
    int n, l;
    scanf(" %d", &n);
    scanf(" %d", &l);

    char tab[n][l]; /*This line is marked as "expression must have constant value" */
    return 0;
}

• Configurations in c_cpp_properties.json: none

Additional context
It works well with v1.7.1, but after switching to Insiders channel IntelliSense shows errors.

[Colengms]

Hi @rico305 . Are you using a GCC compiler/IntelliSenseMode? I'm able to repro the issue if I use GCC on Windows. In my case, the issue appears to be related to -fms-extensions (which should be enabled by default for Cygwin and MinGW). We had 'fixed' this in v1.8.0-insider2, but it exposed some other issues. If this is what you are encountering, you should be able to work around it by adding a compilerArg of -fno-ms-extensions. We plan to disable -fms-extensions for MinGW and Cygwin in the next insiders/release, until we can address the immediate issues. Re-enabling it is then tracked by: #8353 I've opened a bug internally against VS related to -fms-extensions breaking VLAs. (The C/C++ extension shares the IntelliSense implementation with VS).

[patrykkozuch]

Yes, I use GCC compiler - MinGW under Windows. You're right - adding -fno-ms-extensions to compilerArgs works. Thank's for your attention!

[sean-mcmanus]

Fixed with https://github.com/microsoft/vscode-cpptools/releases/tag/1.8.0-insiders3 or 1.8.0 (via using VS Code's "Pre-Release Version" UI or https://marketplace.visualstudio.com/items?itemName=ms-vscode.cpptools&ssr=false#version-history ).

Unless you're explicitly adding -fms-extensions, in which case that bug fix is still pending (#8353 ).