What can cause fwrite to hang?

StackOverflow https://stackoverflow.com/questions/3686888

  •  02-10-2019
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Question

My code is hanging fwrite with the following stack:

libc.so.6.1::___lll_lock_wait
libc.so.6.1::fwrite

This seems to be happening in solaris.

Only incorrect thing which I can think of is that my code may try to do a parallel fclose on the same FILE pointer which is used for doing fwrite. If a parallel fclose happens will it lead to this kind of a stack?

But, I am not sure if the parallel fclose call really did happen or not?

What could be the problem here?

Was it helpful?

Solution

Looks like something has blown up somewhere. Operations on FILE* normally uses an internal lock to be thread safe. You've likely done something to invoke undefned behavior somewhere. E.g. you've corrupted the heap, overwriting something important(like a FILE), or the FILE* has been closed - in which case you can't rely on anything sane to happen if you continue to use it.

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