False negative: memleak is missed when main uses a trailing return type

[Rodri]

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

In the following C++ program, cppcheck should report a memleak warning because memory allocated by malloc is never released. However, cppcheck reports no such warning.

#include <stdlib.h>

auto main() -> int {
  int result = 0;
  auto a = static_cast<char *>(malloc(10));
  if (a) {
    a[0] = 0;
    result = a[0];
  }
  return result;
}

If malloc(10) succeeds, a is returned from main without being passed to free(a), so the allocation is leaked.

The false negative is caused by the trailing return type form of main, not by the static_cast. With int main(), cppcheck reports the leak even when the allocation is written as auto a = static_cast<char *>(malloc(10));. With auto main() -> int, cppcheck misses the leak.

Actual result

Cppcheck reports no memleak warning for the program.

Expected result

Cppcheck should report memleak for a.

Verification

The issue was reproduced with:

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

Version: 2.21.0

[CHR]

With head:

test.cpp:8:3: error: Memory leak: a [memleak]
  return result;
  ^

[Rodri]

Thanks for checking. My report was based on cppcheck 2.21.0. Since HEAD reports the memleak warning correctly, this appears to have already been fixed.