I am attempting to open the current process's executable file for read-write operations (I have additional data attached to the executable), however std::fstream will not open the file in ios::in | ios::out | ios::binary mode, even though open() will (with O_RDWR flag set).
Does anyone know why std::fstream will not open the file, while open() will, and if so, how I can get std::fstream to open the file?
I'd wonder if, somewhere, under the hood, the std::fstream version is calling open - I would bet so. Have you tried checking errno anyways, or perhaps running strace to see what, if any errors, the system call is returning?
It most probably has to do with file sharing semantics. See this thread which deals with a similar question - and the answer there is "The concept of file protection, file sharing, file permissions is OS-specific, which is why it is not covered by standard C++".