Why doesn't strace catch all file accesses?

I'm trying to use strac开发者_运维知识库e to monitor all file accesses by g++ but it only seems to catch read accesses. Why isn't the file access for the output file shown?

g++ calls other programs to do part of the build. If you want strace to trace those child processes, you need to use 'strace -f'.

g++ is just the frontend. It pipes the output to as directly.