On 26 Nov 2001, Oleg Goldshmidt wrote: > > What is this last return statement?? Returning from main? That's not > > something you're supposed to do in a multithreaded program. It > > might, for example, free the entire malloc pool, including argwhich > > is later freed in the second thread, causing a segmentation fault. > > You are right that there should not be a return statement, but it is > not what is happening: free() is OK, according to the > debugger.
the fact that in this specific code you didn't have a problem, does not prove it is correct. the debugger can only be used to show when you _do_ have a race condition - it cannot be used to prove there is _no_ race condition. > Besides, return from main(), as well as any exit(), should > terminate the process (including any threads), freeing the memory by > independent means, not execute the rest of the code, buggy as it may > be. not true at all. the main thread is just a thread. when it calls exit(), the other threads may still be executing, and theoretically, there could be a context switch in the middle of the exit() function, and this might cause a race. when you handle multi-threading, you are not allowed to say "it won't happen" - because one day it will, and the problem won't be persistant and easy to debug. it'll come and go intermitently. as for the bug itself - you are not allowed to pass a NULL pointer as the first parameter of pthread_create() - you must pass a pointer to a pthread_t instance. so you should add a variable definition before calling pthread create: pthread_t thr; and then: if (pthread_create(&thr, NULL, start, arg) != 0) .. this solves the crash. why this happens only during thread termination? i would imagine that when a thread terminates, it atempts to updated its state info (e.g. storing its return value somewhere) - and that state info is quite likely to be stored inside the pthread_t variable passed to pthread_create. -- guy "For world domination - press 1, or dial 0, and please hold, for the creator." -- nob o. dy ================================================================= To unsubscribe, send mail to [EMAIL PROTECTED] with the word "unsubscribe" in the message body, e.g., run the command echo unsubscribe | mail [EMAIL PROTECTED]
