cppcheck 2.13.0: FP invalidLifetime

[Valentin Batz]

The following code produces a false positive regarding the check [invalidLifetime]

#include <iostream>
#include <memory>
#include <string>

void log_format(const char *msg) {
  int size;
  int max;
  std::string str;
  {
    char buf[256];
    max = (int)sizeof(buf);
    size = snprintf(buf, sizeof(buf), "fmt %s", msg);
    if (size < 0) {
      std::cerr << "snprintf failed\n";
    } else if (size <= max) {
      str.assign(buf);
    }
  }
  if (size > max) {
    std::unique_ptr<char[]> buf(new char[size]);

    size = snprintf(buf.get(), std::size_t(size), "fmt %s", msg);
    if (size >= 0) {
      str.assign(buf.get());
    } else {
      std::cerr << "snprintf failed\n";
    }
  }
  std::cerr << str;
}

Error output from cppcheck 2.13.0:

lifetime.cpp:29:16: error: Using object that points to local variable 'buf' that is out of scope. [invalidLifetime]
  std::cerr << str;
               ^
lifetime.cpp:24:25: note: Raw pointer to smart pointer created here.
      str.assign(buf.get());
                        ^
lifetime.cpp:24:25: note: Added to container 'str'.
      str.assign(buf.get());
                        ^
lifetime.cpp:20:29: note: Variable created here.
    std::unique_ptr<char[]> buf(new char[size]);
                            ^
lifetime.cpp:29:16: note: Using object that points to local variable 'buf' that is out of scope.
  std::cerr << str;

[CHR]

Thanks for reporting, ticket is here: https://trac.cppcheck.net/ticket/12568