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