CLi crash when calling with numerical fuzzingEngineFlags

[tstehr]

The CLI crashes ungracefully when trying to pass an argument that looks numerical to the fuzzingEngineFlags. I discovered this while trying to pass -max_total_time 60 to libFuzzer.

Note that this was a typo on my side, the correct argument is -max_total_time=60

To reproduce, run the following:

> yarn run jazzer fuzz.js corpus -- -max_total_time 60
==71008== Uncaught Exception: Jazzer.js: flag.startsWith is not a function
TypeError: flag.startsWith is not a function
    at /project/node_modules/@jazzer.js/core/core.ts:188:9
    at Array.some (<anonymous>)
    at prepareLibFuzzerArg0 (/project/node_modules/@jazzer.js/core/core.ts:186:47)
    at buildFuzzerOptions (/project/node_modules/@jazzer.js/core/core.ts:380:10)
    at startFuzzingNoInit (/project/node_modules/@jazzer.js/core/core.ts:172:24)
    at startFuzzing (/project/node_modules/@jazzer.js/core/core.ts:138:8)

The underlying issue seems to be yargs silently converting numerical-looking arguments into numbers.

[bertschneider]

Thanks for the bug report and analysis! As we're in the process of streamlining parameter handling and already changed quite a bit of code in that area, I added a fix directly to #530 to prevent complicated merge conflicts.

In the future this situation should print a message like:

WARNING: unrecognized flag '-max_total_time'; use -help=1 to list all flags

ERROR: The required directory "10" does not exist

Admittedly not the nicest one but it should point to the problem good enough.

[bertschneider]

Forgot about this issue, sorry. The mentioned PR was already merged some time back, so I will close this issue for now. Thx again for bringing it up 👍