Why do I get segfault here? I cant see it? wht am I doing wrong??Code:struct sched_param *sp_daemon; sp_daemon = alloca(sizeof(*sp_daemon)); sp_daemon->sched_priority = SCHED_SS_DAEMON_PRIORITY; //Just some high RT prio printf("THIS GETS PRINTED"); if(pthread_setschedparam(pthread_self(), SCHED_FIFO, sp_daemon)) { perror("1. pthread_setschedparam failed!"); return -1; } printf("GET SEGFAULT BEFORE I GET HERE");
Is alloca() really what you want here? If you want a local variable on the stack, then just use one. If you want to ALLOCATE some memory for your structure, then use malloc() or similar.
alloca is great for when you need some function-local dynamic (and relatively small) space.
--
Mats
Compilers can produce warnings - make the compiler programmers happy: Use them!
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> if(pthread_setschedparam(pthread_self(), SCHED_FIFO, sp_daemon))
The memory you pass to a thread needs to have a lifetime which is at least as long as the life of the calling function, and the life of the thread which is to be run.
Local variables don't normally fall into this category.
If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
If at first you don't succeed, try writing your phone number on the exam paper.
