On Dec 9, 2007 2:12 PM, Yi Wang <yi.w@xxxxxxxx> wrote: > > Hi, all > I read from some book that a signal handler can either return or call exit, abort or longjmp, it is permitted by ANSI C. > However, I remember that lonjmp never returns, which in turn causes the signal handler can not return. In that case, the kernel will think the program is in signal handler forever, am I right? > IMHO, I think that is too bad... This is not the case. Rather than returning to the interrupted statement, longjmp causes control to be sent back to the setjmp() in the main program. Since POSIX.1 does not specify whether setjmp and longjmp save or restore the current set of blocked signals the use of sigsetjmp/siglongjmp is recommended if signals must be handled. longjmp does not return because setjmp first saves the environment to which longjmp can return from another point in the program. After returning to setjmp the process does not know that it "has been returned" from somewhere else. So, technically longjmp cannot not return. A problem with the use of setjmp/longjmp is that the environment will not be cleaned up (closing FDs, flushing buffers, freeing heap-allocated memory, and the like). \Steve -- Steve Grägert DigitalEther.de - To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
