False negative: file resource leaks missed in loop with early returns

[Rodri]

Hi, I found a false negative regarding the rule resourceLeak.

Cppcheck reports resourceLeak for the first program, but it misses the second program, which leaks file resources through a loop and early-return paths.

First program

#include <stdio.h>

int main()
{
    const FILE *a = fopen("good.c", "r");
    if (!a)
        return 0;

    return 0;
}

Cppcheck reports:

<error id="resourceLeak" severity="error" msg="Resource leak: a" ...>

Second program

#include <stdio.h>

int main() {
  const FILE *a = fopen("good.c", "r");
  if (!a)
    return 0;
  for (int i = 0; i < 5; i++) {
    FILE *b = fopen("temp.c", "r");
    if (!b)
      return 0;
    char c = fgetc(b);
    if (c == 'X') {
      return 0;
    }
    fclose(b);
  }
  return 0;
}

In this program, a is never closed after a successful fopen. In addition, when c == 'X', the function returns before fclose(b), so b is also leaked on that path.

Actual result

Cppcheck reports no resourceLeak warning for the second program.

Expected result

Cppcheck should report resourceLeak for a, and it should also report a leak for b on the c == 'X' early-return path.

Verification

The issue was reproduced with:

cppcheck --output-format=xmlv2 --enable=all resource_leak_loop_early_return.cpp

Version: 2.21.0

[CHR]

Looks like an instance of https://trac.cppcheck.net/ticket/2565