avr-libc: <setjmp.h>: Non-local goto AVR Libc Home Page AVR Libc Development Pages Main Page User Manual Library Reference FAQ Alphabetical Index Example Projects <setjmp.h>: Non-local gotoDetailed Description While the C language has the dreaded goto statement, it can only be used to jump to a label in the same (local) function. In order to jump directly to another (non-local) function, the C library provides the setjmp() and longjmp() functions. setjmp() and longjmp() are useful for dealing with errors and interrupts encountered in a low-level subroutine of a program. Note:setjmp() and longjmp() make programs hard to understand and maintain. If possible, an alternative should be used. longjmp() can destroy changes made to global register variables (see How to permanently bind a variable to a register?). For a very detailed discussion of setjmp()/longjmp(), see Chapter 7 of Advanced Programming in the UNIX Environment, by W. Richard Stevens. Example: #include <setjmp.h> jmp_buf env; int main (void) { if (setjmp (env)) { ... handle error ... } while (1) { ... main processing loop which calls foo() some where ... } } ... void foo (void) { ... blah, blah, blah ... if (err) { longjmp (env, 1); } } Functions int setjmp (jmp_buf __jmpb) void longjmp (jmp_buf __jmpb, int __ret) __ATTR_NORETURN__ Function Documentation void longjmp ( jmp_buf  __jmpb, int  __ret  ) Non-local jump to a saved stack context. #include <setjmp.h> longjmp() restores the environment saved by the last call of setjmp() with the corresponding __jmpb argument. After longjmp() is completed, program execution continues as if the corresponding call of setjmp() had just returned the value __ret. Note:longjmp() cannot cause 0 to be returned. If longjmp() is invoked with a second argument of 0, 1 will be returned instead. Parameters: __jmpb Information saved by a previous call to setjmp(). __ret Value to return to the caller of setjmp(). Returns:This function never returns. int setjmp ( jmp_buf  __jmpb  )  Save stack context for non-local goto. #include <setjmp.h> setjmp() saves the stack context/environment in __jmpb for later use by longjmp(). The stack context will be invalidated if the function which called setjmp() returns. Parameters: __jmpb Variable of type jmp_buf which holds the stack information such that the environment can be restored. Returns:setjmp() returns 0 if returning directly, and non-zero when returning from longjmp() using the saved context. Automatically generated by Doxygen 1.5.6 on 4 Dec 2008.