fix #381

[foryoung365]

std::fstream fs(simplePath, std::ios::app);

File existence check using fstream with ios::app is implemented as a workaround because:

• ifstream::good() incorrectly handles directories on Unix-like systems
• <sys/stat.h> adds platform-specific dependencies
• It avoids duplication with CppCheck's 'path' implementation
• std::filesystem (the proper solution) requires C++17 support

[firewave]

That is an interesting handling.

[foryoung365]

This solution still has flaws; when the file does not exist, an empty file will be created. Therefore, I replaced it with

std::fstream fs(simplePath, std::ios::in|std::ios::out);

Here is a simple test result (linux, mac, and windows):
https://github.com/foryoung365/CppFstreamTest/actions/runs/11549258974

Here are some references:
https://en.cppreference.com/w/cpp/io/basic_filebuf/open

[firewave]

FYI I used this in #435 to improve the checks in the CLI.

[firewave]

That check is also flawed because it will fail if the files are read-only.

[firewave]

Thanks. Please give me a few days since I might be out sick.

[danmar]

how do we test this? you can easily check if a file exists or not in a unit test but if you need to test various edge cases I guess a pytest working in a tempdir is better.

[firewave]

The issue referenced here was fixed in #443. So I think this can be closed.

And #339 contains improved code for checking for the existence of a file/directory.

I also filed https://trac.cppcheck.net/ticket/14133 about detecting such code with Cppcheck.