fuzzing/printf: exit code differs

[oss-fuzz-robot]

OSS-Fuzz has found a bug in this project. Please see https://oss-fuzz.com/testcase?key=5970261954330624 for details and reproducers.

This issue is mirrored from https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=65496 and will auto-close if the status changes there.

If you have trouble accessing this report, please file an issue at https://github.com/google/oss-fuzz/issues/new.

[sylvestre]

hmm, i wonder if this isn't a thread issue here

	Test completed with discrepancies for printf: ["%x", "%786"]
	Running test ["printf", "%b", "842"]
	Test Type: printf
	Input: ["%b", "842"]
	Rust exit code: 1
	GNU exit code: 0
	Discrepancy detected: exit code differs

[samueltardieu]

If you run the fuzzers, you'll see that it happens in a test which runs just after an unsuccessful (but matching) test has been executed. This led me to explore whether you might use global variables somewhere, and you do… for the exit code (amongst others).

I think this is a very bad idea to do so, and the most sensible plan would be to eliminate all global state. I'll submit a PR nontheless so that the fuzzer does not crash on it. Note that this would still not allow multi-threaded fuzzers to run correctly, but I don't know if those exist (most will create multiple processes).