False negative: empty() call suppresses later accessMoved warning for decltype string

[Rodri]

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

Cppcheck reports accessMoved when a moved std::string declared through decltype(std::string{"test"}) is accessed directly. However, if that moved-from object is first queried with empty(), cppcheck misses the later access.

#include <iostream>
#include <string>
#include <utility>

int main() {
  decltype(std::string{"test"}) s = "test";
  std::string n = std::move(s);
  if (s.empty()) {
  }
  std::cout << s << '\n' << std::flush;
  return 0;
}

Here, decltype(std::string{"test"}) is std::string. The object s is moved into n, and then s is accessed by s.empty() and by std::cout << s.

If the if (s.empty()) block is removed, cppcheck reports accessMoved for the stream insertion. A plain std::string s version also reports accessMoved, even with the empty() call. The warning is missed for the combination of the decltype(std::string{"test"}) declaration and the empty() query before the later access.

Actual result

Cppcheck reports no accessMoved warning.

Expected result

Cppcheck should report accessMoved for the access to s after std::move(s).

Verification

The issue was reproduced with:

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

Version: 2.21.0

[CHR]

I'm getting a warning. Are you passing --inconclusive?

test.cpp:5:7: warning: inconclusive: Access of moved variable 's'. [accessMoved]
  if (s.empty()) {
      ^