CAF runs a customized version of libc, which at least intercepts all of the file descriptor related functions and detects things like double closes of a file descriptor. We don't seem to have code which performs this type of checking, and I think it would good to do this, at least in debug builds. Bug 1073088 would have benefited from this. In that case, the bug was in the original code which had been in the tree for about a month. CAF caught it during their stability tests, and this then causes a mad scramble to find the problem and fix it. If we had the extra checking, then we could have caught it and fixed it a month ago. For B2G, the simplest way to implement this seems to be to shadow all of the file descriptor functions (open/close/dup and friends, etc) in mozglue and track the open status of each file descriptor in private data structures.