ref: e73ce8475e683c62d0335a18788d86ae92a010f0
dir: /sys/man/2/setjmp/
.TH SETJMP 2 .SH NAME setjmp, longjmp, notejmp \- non-local goto .SH SYNOPSIS .B #include <u.h> .br .B #include <libc.h> .PP .ta \w'\fLvoid 'u .B int setjmp(jmp_buf env) .PP .B void longjmp(jmp_buf env, int val) .PP .B void notejmp(void *uregs, jmp_buf env, int val) .SH DESCRIPTION These routines are useful for dealing with errors and interrupts encountered in a low-level subroutine of a program. .PP .I Setjmp saves its stack environment in .I env for later use by .IR longjmp . It returns value 0. .PP .I Longjmp restores the environment saved by the last call of .IR setjmp . It then causes execution to continue as if the call of .I setjmp had just returned with value .IR val . The invoker of .I setjmp must not itself have returned in the interim. All accessible data have values as of the time .I longjmp was called. .PP .I Notejmp is the same as .I longjmp except that it is to be called from within a note handler (see .IR notify (2)). The .I uregs argument should be the first argument passed to the note handler. .PP .I Setjmp and .I longjmp can also be used to switch stacks. Several macros are defined in .B /$objtype/include/u.h that can be used to build .B jmp_bufs by hand. The following code establishes a .B jmp_buf .i label that may be called by .I longjmp to begin execution in a function .BR f with 1024 bytes of stack: .IP .EX #include <u.h> #include <libc.h> jmp_buf label; #define NSTACK 1024 char stack[NSTACK]; void setlabel(void) { label[JMPBUFPC] = ((ulong)f+JMPBUFDPC); /* -2 leaves room for old pc and new pc in frame */ label[JMPBUFSP] = (ulong)(&stack[NSTACK-2*sizeof(ulong*)]); } .EE .SH SOURCE .B /sys/src/libc/$objtype/setjmp.s .br .B /sys/src/libc/$objtype/notejmp.c .SH SEE ALSO .IR notify (2) .SH BUGS .PP .I Notejmp cannot recover from an address trap or bus error (page fault) on the 680x0 architectures.