SuperC documentation

⚠️ This is a PROPOSAL DRAFT. Defer auto is currently not implemented. Syntax may change
Development is not going to advance until LLVM backend is minimally stable.

Defer in scoped blocks

Will execute the code stated right before exiting a syntactical scope.

Sometimes it’s useful to execute code after a scoped block, not only in a function scope.

defer auto runs at…

Examples

#include <stdio.h>

int main() {
  int x = 8;

  {
    int *mem = malloc(sizeof(int));
    defer auto {
      free(mem);
      printf("mem is freed here\n");
    }

    *mem = 42 + x;
    printf("%d\n", *mem);
  }

  printf("OK\n");

  // 50
  // mem is freed here
  // OK
  return 0;
}

#include <stdio.h>

int main() {
  int x = 8;

  {
    defer auto printf("I am unavoidable\n");
    // Try to escape defer execution
    goto lbl_end;
    printf("Unreachable\n");
  }

  lbl_end:
  printf("OK\n");

  // I am unavoidable
  // OK
  return 0;
}

#include <stdio.h>
#include <stdbool.h>

int main() {
  while (true) {
    defer auto printf("A\n");
    while (true) {
      defer auto printf("B\n");
      while (true) {
        defer auto printf("C\n");
        // Exit 3 loops
        // Executing defers in LIFO order
        break 3;
      }
    }
  }

  printf("OK\n");
  // C
  // B
  // A
  // OK
  return 0;
}

Defer in loops

In addition, defer auto has a special behavior in loops.

It runs also before the continue/break statements. So the defer statement is executed at the end of every iteration. This also applies for break n.

Examples

#include <stdio.h>

int main() {

  for (int i = 0; i < 5; i++) {
    char *str = malloc(100); // 100 chars max
    defer auto free(str);

    if (i == 1)
      continue; // -> defer runs here

    sprintf(str, "Number: %d", i);
    printf("%s\n", str);

    if (i == 3)
      break; // -> defer runs here

    // -> defer runs here
  }

  printf("OK\n");

  // Number: 0
  // Number: 2
  // Number: 3
  // OK
  return 0;
}

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