I have an executable (fossil scm) that is being invoked by my program externally through ::CreateProcess windows call. The stdout and stderr are then captured. Since the source code for fossil is available, I would prefer to create a static library out of it and issue calls directly. Currently, communication to fossil is done through the command line parameters, and the communication back is through the process return code, stdout and stderr. Fossil writes to stdout/err through printf and fprintf calls.

What is the best way to solve this with minimum alteration of fossil source? Is there a reliable and cross-platform way to intercept stdout/err and send it into a memory buffer?