I am working on a program, which uses multiple std::ifstreams for reading a binary file, one std::ifstream for each thread. Now I need to know, if std::ofstream is thread-safe on Windows and Linux for writing in a same file. I am using using only one std::ofstream and using for multiple threads.
I am reading different blocks using using each thread and writing those block in output file using seekp() and write(). Currently it is working for me but whether it is problematic for big files.
Is std::ofstream thread safe?
From C++ standards (Input/Output Library Thread Safety):
27.1.3 Thread safety [iostreams.thread-safety]
Concurrent access to a stream object [string.streams, file.streams], stream buffer object [stream.buffers], or C Library stream [c.files] by multiple threads may result in a data race [intro.multithread] unless otherwise specified [iostream.objects]. [Note: Data races result in undefined behavior [intro.multithread].