You can add a constructor and destructor functions to a C program; the constructor function runs before main() and the destructor after main().

The syntax is not exactly clean or obvious (those are double underscores before and after the word attribute like Python dunders!) but I got this program to compile/run with clang 10 on Ubuntu as the screenshot shows.  Here’s a listing. I called the two functions ctor and dtor but you can use anything.

#include <stdio.h>

__attribute__((constructor)) void ctor(void)
{
  printf("Constructor runs first\n");
}

__attribute__((destructor)) void dtor(void)
{
  printf("Destructor runs last\n");
}

int main() {
    printf("Main\n");
}

The output  is:

david@DavidPC:~/Projects/Examples$ ./ex1
Constructor runs first
Main
Destructor runs last

I was curious as to how many C extensions there are for VS Code. If you visit the marketplace (not a great name- all are free-some market!) in a browser, you can search through the (currently) 24,779 available extensions.

Finding C extensions is not easy. A search for C returns almost 16,000 results. C++  is a better thing to search on and gives 207 results, many of which are for C and C++. You can also search in VS Code but it’s easier in a web browser.

Even that’s probably too much but you can use the showing pull down to see how many extensions are in the various categories. If for instance you select Debuggers, then you will only see 18 extensions.

Note: As I’m still only my old creaky Ubuntu laptop, I had to use scrot for screen capture and gthumb for editing the image.  Note, the scrot project is looking for a programmer to look after it. Here is how to contribute to the project.