According to this page https://openexr.com/en/latest/ReadingAndWritingImageFiles.html ==== You may have noticed that in the example above, there are no explicit checks to verify that writing the file actually succeeded. If the OpenEXR library detects an error, it throws a C++ exception instead of returning a C-style error code. With exceptions, error handling tends to be easier to get right than with error return values. For instance, a program that calls our writeRgba1() function can handle all possible error conditions with a single try/catch block: 1 try 2 { 3 writeRgba1 (fileName, pixels, width, height); 4 } 5 catch (const std::exception &exc) 6 { 7 std::cerr << exc.what() << std::endl; 8 } ===== I guess this mechanism was not very refined in c++98, so it was not used in Cinelerra. Then come I and made EXR one of choices in background render (where error handling apparently matters). I hope one call per frame will not slow us down much .... and better slower than crash?