Setjmp/longjmp updates and cleanup.
This commit is contained in:
David van Moolenbroek
parent
170a72fd61
commit
d4e6fe3546
16 changed files with 232 additions and 345 deletions
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@ -1,87 +0,0 @@
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/* This file is intended for use by assembly language programs that
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* need to manipulate a jmp_buf. It may only be used by those systems
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* for which a jmp_buf is identical to a struct sigcontext.
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*/
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#ifndef _JMP_BUF_H
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#define _JMP_BUF_H
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#if !defined(CHIP)
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#include "error, configuration is not known"
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#endif
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#if (CHIP == INTEL)
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#if _WORD_SIZE == 4
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#define JB_FLAGS 0
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#define JB_MASK 4
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#define JB_GS 8
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#define JB_FS 10
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#define JB_ES 12
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#define JB_DS 14
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#define JB_DI 16
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#define JB_SI 20
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#define JB_BP 24
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#define JB_ST 28
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#define JB_BX 32
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#define JB_DX 36
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#define JB_CX 40
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#define JB_AX 44
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#define JB_RETADR 48
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#define JB_IP 52
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#define JB_CS 56
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#define JB_PSW 60
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#define JB_SP 64
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#define JB_SS 68
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#else /* _WORD_SIZE == 2 */
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#define JB_FLAGS 0
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#define JB_MASK 2
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#define JB_ES 6
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#define JB_DS 8
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#define JB_DI 10
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#define JB_SI 12
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#define JB_BP 14
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#define JB_ST 16
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#define JB_BX 18
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#define JB_DX 20
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#define JB_CX 22
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#define JB_AX 24
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#define JB_RETADR 26
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#define JB_IP 28
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#define JB_CS 30
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#define JB_PSW 32
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#define JB_SP 34
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#define JB_SS 36
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#endif /* _WORD_SIZE == 2 */
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#else /* !(CHIP == INTEL) */
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#if (CHIP == M68000)
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#define JB_FLAGS 0
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#define JB_MASK 2
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#define JB_RETREG 6
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#define JB_D1 10
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#define JB_D2 14
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#define JB_D3 18
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#define JB_D4 22
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#define JB_D5 26
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#define JB_D6 20
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#define JB_D7 34
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#define JB_A0 38
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#define JB_A1 42
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#define JB_A2 46
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#define JB_A3 50
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#define JB_A4 54
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#define JB_A5 58
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#define JB_A6 62
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#define JB_SP 66
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#define JB_PC 70
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#define JB_PSW 74
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#else /* !(CHIP == INTEL) && !(CHIP == M68000) */
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#include "error, CHIP is not supported"
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#endif /* (CHIP == INTEL) */
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/* Defines from C headers needed in assembly code. The headers have too
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* much C stuff to used directly.
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*/
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#define SIG_BLOCK 0 /* must agree with <signal.h> */
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#define SC_SIGCONTEXT 2 /* must agree with <sys/sigcontext.h> */
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#define SC_NOREGLOCALS 4 /* must agree with <sys/sigcontext.h> */
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#endif /* _JMP_BUF_H */
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158
include/setjmp.h
158
include/setjmp.h
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@ -1,67 +1,51 @@
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/* The <setjmp.h> header relates to the C phenomenon known as setjmp/longjmp.
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* It is used to escape out of the current situation into a previous one.
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* A typical example is in an editor, where hitting DEL breaks off the current
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* command and puts the editor back in the main loop, though care has to be
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* taken when the DEL occurs while executing a library function, since
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* some of them are not reentrant.
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*
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* POSIX does not require the process signal mask to be saved and restored
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* during setjmp/longjmp. However, the current implementation does this
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* in order to agree with OSF/1 and other BSD derived systems.
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* The actual implementations of all these functions and, by extension, parts
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* of this header, are both compiler- and architecture-dependent. Currently
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* two compilers are supported: ACK and GCC. Each of these has their own
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* implementation of the functions in their runtime system library code.
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* As it is impossible to predict the requirements for any other compilers,
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* this header may not be compatible with such other compilers either.
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*
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* The pair of functions _setjmp/_longjmp may be used when the signal
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* mask is not to be saved/restored. These functions are traditional
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* in BSD systems.
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* The ACK compiler will not enregister any variables inside a function
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* containing a setjmp call, even if those variables are explicitly declared
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* as register variables. Thus for ACK, of all the registers, only the
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* program counter, stack pointer and frame pointer have to be saved into the
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* jmp_buf structure. This makes the jmp_buf structure very small, and
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* moreover, the implementation of the setjmp/longjmp calls (written in EM)
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* architecture-independent and thus very portable. The ACK compiler
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* recognizes only the symbol __setjmp as being such a setjmp call.
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*
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* There are different ways of implementing setjmp/longjmp. Probably
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* the best way is to unify it with signal handling. This is true for the
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* following reasons: Both setjmp/longjmp and signal delivery must save
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* a context so that it may be restored later. The jmp_buf necessarily
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* contains signal information, namely the signal mask to restore. Both
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* longjmp and the return of a signal handler must trap to the operating
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* system to restore the previous signal mask. Finally, the jmp_buf
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* and the sigcontext structure contain the registers to restore.
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* The GCC compiler recognizes all of the setjmp/_setjmp/__setjmp name
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* variants as calls to setjmp functions, and treats them as special
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* accordingly, but does require that the setjmp implementation save and
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* restore most of the registers. It has no portable setjmp and longjmp
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* functions like ACK, and therefore has to have enough space in the jmp_buf
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* structure to store the registers on any architecture it's ported to.
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*
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* Some compilers, namely ACK, will not enregister any variables inside a
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* function containing a call to setjmp, even if those variables are
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* explicitly declared as register variables. Thus for ACK, the
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* identification of the jmp_buf with a sigcontext structure would cause
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* unnecessary overhead: the jmp_buf has room for all the registers, but
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* the only registers that need to be saved are the stack pointer,
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* frame pointer, and program counter.
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* Taking the common denominator of both compilers, the function definitions
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* in this header rely on the presence of merely two functions: __setjmp and
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* longjmp. On the other hand, the size of jmp_buf depends on the compiler
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* used: for ACK, jmp_buf is exactly big enough to store the three mentioned
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* registers; for GCC and any other compiler, the size is chosen in such a
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* way that it's likely to offer enough room to store registers for any
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* architecture. The POSIX sigjmp_buf is identical to jmp_buf in all cases.
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*
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* So, for ACK a jmp_buf is much smaller than a sigcontext structure, and
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* longjmp does not directly call sigreturn. Instead, longjmp calls a
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* front-end function which initializes the appropriate fields of a
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* sigcontext structure, marks this structure as containing no valid
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* general purpose registers, and then calls sigreturn.
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* As far as porting is concerned --
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*
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* The POSIX sigjmp_buf is identical to the jmp_buf in all cases.
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* All code writers/porters that have to deal with the actual contents of the
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* jmp_buf structure in one way or another, should look at <sys/jmp_buf.h>.
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*
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* Different compilers have different symbols that they recognize as
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* setjmp symbols. ACK recognizes __setjmp, the GNU C compiler
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* recognizes setjmp and _setjmp, and BCC recognizes all three.
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* When these symbols occur within a function, the compiler may keep
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* all local variables on the stack, avoid certain optimizations, or
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* pass hidden arguments to the setjmp function.
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*
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* Thus, setjmp implementations vary in two independent ways which may
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* be identified through the following preprocessor tokens:
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* Porters of a new compiler to Minix have to make sure the compiler
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* recognizes at least __setjmp as a setjmp call (if applicable) and provide
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* library implementations of __setjmp and longjmp conforming to their
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* declarations below; if this is not possible, compiler-specific code will
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* have to be added to this header.
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*
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* _SETJMP_SYMBOL -- If 0, this means the compiler treats setjmp and _setjmp
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* specially. If 1, this means the compiler treats __setjmp specially.
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*
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* _SETJMP_SAVES_REGS -- If 1, this means setjmp/longjmp must explicitly
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* save and restore all registers. This also implies that a jmp_buf is
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* different than a sigcontext structure. If 0, this means that the compiler
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* will not use register variables within a function that calls one of
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* its SETJMP_SYMBOLs.
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*
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* When _SETJMP_SYMBOL = 1, the implementation has a few dozen bytes of
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* unnecessary overhead. This happens in the following manner: a program uses
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* _setjmp/_longjmp because it is not interested in saving and restoring the
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* signal mask. Nevertheless, because _setjmp expands to the general purpose
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* function __setjmp, code for sigprocmask(2) is linked into the program.
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* Porters of Minix+GCC to other architectures have to make sure that the
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* __regs array of the jmp_buf structure is large enough to hold all the
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* registers the __setjmp implementation for that architecture has to save.
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*/
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#ifndef _SETJMP_H
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@ -71,82 +55,34 @@
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#include <ansi.h>
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#endif
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#if !defined(__ACK__) && !defined(__BCC__) && !defined(__GNUC__)
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#define __ACK__
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#endif
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#ifdef __ACK__
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#define _SETJMP_SYMBOL 1
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#define _SETJMP_SAVES_REGS 0
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#endif
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#ifdef __BCC__
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#define _SETJMP_SYMBOL 0
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#define _SETJMP_SAVES_REGS 1
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#endif
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#ifdef __GNUC__
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#define _SETJMP_SYMBOL 1
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#define _SETJMP_SAVES_REGS 1
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#endif
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/* The jmp_buf data type. Do not change the order of these fields -- some
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* C library code refers to these fields by name. When _SETJMP_SAVES_REGS
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* is 1, the file <sys/jmp_buf.h> gives the usage of the sixteen registers.
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*/
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typedef struct {
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int __flags; /* XXX - long might give better alignment */
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long __mask; /* must have size >= sizeof(sigset_t) */
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#if (_SETJMP_SAVES_REGS == 0)
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#if defined(__ACK__)
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_PROTOTYPE(void (*__pc),(void)); /* program counter */
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void *__sp; /* stack pointer */
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void *__lb; /* local base (ACKspeak for frame pointer) */
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#else
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void *__regs[16]; /* size is machine dependent */
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long __mask; /* must have size >= sizeof(sigset_t) */
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int __flags;
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#else /* GCC */
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int __flags; /* XXX - long might give better alignment */
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long __mask; /* must have size >= sizeof(sigset_t) */
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void *__regs[16]; /* actual use is architecture dependent */
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#endif
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} jmp_buf[1];
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#if (_SETJMP_SYMBOL == 1)
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_PROTOTYPE( int __setjmp, (jmp_buf _env, int _savemask) );
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_PROTOTYPE( void longjmp, (jmp_buf _env, int _val) );
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_PROTOTYPE(int sigjmp, (jmp_buf _jb, int _retval) );
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#define setjmp(env) __setjmp((env), 1)
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#ifdef _MINIX
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#define _setjmp(env) __setjmp((env), 0)
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_PROTOTYPE(void _longjmp, (jmp_buf _env, int _val) );
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#define _longjmp(env, val) longjmp((env), (val))
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#endif
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#ifdef _POSIX_SOURCE
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typedef jmp_buf sigjmp_buf;
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#ifdef __GNUC__
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#define siglongjmp longjmp
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#else
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_PROTOTYPE( void siglongjmp, (sigjmp_buf _env, int _val) );
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#endif
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#define sigsetjmp(env, savemask) __setjmp((env), (savemask))
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#define siglongjmp(env, val) longjmp((env), (val))
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#endif /* _POSIX_SOURCE */
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#endif /* _SETJMP_SYMBOL == 1 */
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#if (_SETJMP_SYMBOL == 0)
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_PROTOTYPE( int setjmp, (jmp_buf _env) );
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_PROTOTYPE( void longjmp, (jmp_buf _env, int _val) );
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#ifdef _MINIX
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_PROTOTYPE( int _setjmp, (jmp_buf _env) );
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_PROTOTYPE( void _longjmp, (jmp_buf _env, int _val) );
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#endif
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#ifdef _POSIX_SOURCE
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#define sigjmp_buf jmp_buf
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_PROTOTYPE( void siglongjmp, (sigjmp_buf _env, int _val) );
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/* XXX - the name _setjmp is no good - that's why ACK used __setjmp. */
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#define sigsetjmp(env, savemask) ((savemask) ? setjmp(env) : _setjmp(env))
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#endif /* _POSIX_SOURCE */
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#endif /* _SETJMP_SYMBOL == 0 */
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#endif /* _SETJMP_H */
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45
include/sys/jmp_buf.h
Normal file
45
include/sys/jmp_buf.h
Normal file
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@ -0,0 +1,45 @@
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/* This file is intended for use by program code (possibly written in
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* assembly) that needs to manipulate a jmp_buf or sigjmp_buf. The JB_*
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* values are byte offsets into the jmp_buf and sigjmp_buf structures.
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*/
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#ifndef _JMP_BUF_H
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#define _JMP_BUF_H
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#include <minix/config.h>
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#if defined(__ACK__)
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/* as per lib/ack/rts/setjmp.e */
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/* note the lack of parentheses, which would confuse 'as' */
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#define JB_PC 0
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#define JB_SP JB_PC + _EM_PSIZE
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#define JB_LB JB_SP + _EM_PSIZE
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#define JB_MASK JB_LB + _EM_PSIZE
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#define JB_FLAGS JB_MASK + _EM_LSIZE
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#if (CHIP == INTEL)
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#define JB_BP JB_LB
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#endif
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#elif defined(__GNUC__)
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#if (CHIP == INTEL) && (_WORD_SIZE == 4)
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/* as per lib/gnu/rts/__setjmp.gs */
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#define JB_FLAGS 0
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#define JB_MASK 4
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#define JB_PC 8
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#define JB_SP 12
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#define JB_BP 16
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#define JB_BX 20
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#define JB_CX 24
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#define JB_DX 28
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#define JB_SI 32
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#define JB_DI 36
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#endif /* (CHIP == INTEL) && (_WORD_SIZE == 4) */
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#endif /* __GNU__ */
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#endif /* _JMP_BUF_H */
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@ -136,11 +136,6 @@ struct sigcontext {
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#define sc_psw sc_regs.sr_psw
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#endif /* _MINIX_CHIP == M68000 */
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/* Values for sc_flags. Must agree with <minix/jmp_buf.h>. */
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#define SC_SIGCONTEXT 2 /* nonzero when signal context is included */
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#define SC_NOREGLOCALS 4 /* nonzero when registers are not to be
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saved and restored */
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_PROTOTYPE( int sigreturn, (struct sigcontext *_scp) );
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#endif /* _SIGCONTEXT_H */
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@ -38,19 +38,6 @@ message *m_ptr; /* pointer to request message */
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if (src_phys == 0) return(EFAULT);
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phys_copy(src_phys, vir2phys(&sc), (phys_bytes) sizeof(struct sigcontext));
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/* Make sure that this is not just a jump buffer. */
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if ((sc.sc_flags & SC_SIGCONTEXT) == 0) return(EINVAL);
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/* Fix up only certain key registers if the compiler doesn't use
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* register variables within functions containing setjmp.
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*/
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if (sc.sc_flags & SC_NOREGLOCALS) {
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rp->p_reg.retreg = sc.sc_retreg;
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rp->p_reg.fp = sc.sc_fp;
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rp->p_reg.pc = sc.sc_pc;
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rp->p_reg.sp = sc.sc_sp;
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return(OK);
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}
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sc.sc_psw = rp->p_reg.psw;
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#if (CHIP == INTEL)
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@ -47,7 +47,7 @@ message *m_ptr; /* pointer to request message */
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memcpy(&sc.sc_regs, (char *) &rp->p_reg, sizeof(struct sigregs));
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/* Finish the sigcontext initialization. */
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sc.sc_flags = SC_SIGCONTEXT;
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sc.sc_flags = 0; /* unused at this time */
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sc.sc_mask = smsg.sm_mask;
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/* Copy the sigcontext structure to the user's stack. */
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@ -2,9 +2,7 @@
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LIBRARIES=libc
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libc_FILES=" \
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_longjmp.gs \
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_setjmp.gs \
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longjmp.gs \
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setjmp.gs"
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__setjmp.gs \
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longjmp.gs"
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TYPE=gnu
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31
lib/gnu/rts/__setjmp.gs
Normal file
31
lib/gnu/rts/__setjmp.gs
Normal file
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@ -0,0 +1,31 @@
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/ __setjmp.gnu.s
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/
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/ Created: Oct 14, 1993 by Philip Homburg <philip@cs.vu.nl>
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.text
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.globl ___setjmp
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___setjmp:
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movl 4(%esp), %eax # jmp_buf
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movl %edx, 28(%eax) # save edx
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movl 0(%esp), %edx
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movl %edx, 8(%eax) # save program counter
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movl %esp, 12(%eax) # save stack pointer
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movl %ebp, 16(%eax) # save frame pointer
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movl %ebx, 20(%eax)
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movl %ecx, 24(%eax)
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movl %esi, 32(%eax)
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movl %edi, 36(%eax)
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movl 8(%esp), %edx # save mask?
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movl %edx, 0(%eax) # save whether to restore mask
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testl %edx, %edx
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jz 1f
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leal 4(%eax), %edx # pointer to sigset_t
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pushl %edx
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call ___newsigset # save mask
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addl $4, %esp
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1:
|
||||
movl $0, %eax
|
||||
ret
|
||||
|
||||
/ $PchId: __setjmp.gnu.s,v 1.4 1996/03/12 19:30:54 philip Exp $
|
||||
|
|
@ -1,38 +0,0 @@
|
|||
/ _longjmp.gnu.s
|
||||
/
|
||||
/ Created: Oct 15, 1993 by Philip Homburg <philip@cs.vu.nl>
|
||||
|
||||
.text
|
||||
.globl __longjmp
|
||||
__longjmp:
|
||||
movl 4(%esp), %eax # jmp_buf
|
||||
cmpl $0, 0(%eax) # save mask?
|
||||
je 1f
|
||||
leal 4(%eax), %ebx # pointer to sigset_t
|
||||
pushl %ebx
|
||||
call ___oldsigset # restore mask
|
||||
addl $4, %esp
|
||||
movl 4(%esp), %eax # jmp_buf
|
||||
1:
|
||||
movl 8(%esp), %ecx # result value
|
||||
movl 12(%eax), %esp # restore stack pointer
|
||||
|
||||
movl 8(%eax), %ebx # restore program counter
|
||||
movl %ebx, 0(%esp)
|
||||
|
||||
pushl %ecx # save result code
|
||||
|
||||
movl 16(%eax), %ebp # restore frame pointer
|
||||
movl 20(%eax), %ebx
|
||||
movl 24(%eax), %ecx
|
||||
movl 28(%eax), %edx
|
||||
movl 32(%eax), %esi
|
||||
movl 36(%eax), %edi
|
||||
pop %eax
|
||||
testl %eax, %eax
|
||||
jz 1f
|
||||
ret
|
||||
1: movl $1, %eax
|
||||
ret
|
||||
|
||||
/ $PchId: _longjmp.gnu.s,v 1.4 1996/03/12 19:30:02 philip Exp $
|
||||
|
|
@ -1,35 +0,0 @@
|
|||
/ _setjmp.gnu.s
|
||||
/
|
||||
/ Created: Oct 14, 1993 by Philip Homburg <philip@cs.vu.nl>
|
||||
|
||||
.text
|
||||
.globl ___setjmp
|
||||
___setjmp:
|
||||
movl 4(%esp), %eax # jmp_buf
|
||||
movl %ebx, 20(%eax) # save ebx
|
||||
movl 0(%esp), %ebx
|
||||
movl %ebx, 8(%eax) # save program counter
|
||||
movl %esp, 12(%eax) # save stack pointer
|
||||
movl %ebp, 16(%eax) # save frame pointer
|
||||
movl %ecx, 24(%eax)
|
||||
movl %edx, 28(%eax)
|
||||
movl %esi, 32(%eax)
|
||||
movl %edi, 36(%eax)
|
||||
|
||||
movl 8(%esp), %ebx # save mask?
|
||||
movl %ebx, 0(%eax) # save whether to restore mask
|
||||
|
||||
pushl 20(%eax) # save ebx
|
||||
|
||||
testl %ebx, %ebx
|
||||
jz 1f
|
||||
leal 4(%eax), %ebx # pointer to sigset_t
|
||||
pushl %ebx
|
||||
call ___newsigset # save mask
|
||||
addl $4, %esp
|
||||
1:
|
||||
popl %ebx
|
||||
movl $0, %eax
|
||||
ret
|
||||
|
||||
/ $PchId: _setjmp.gnu.s,v 1.4 1996/03/12 19:30:54 philip Exp $
|
||||
|
|
@ -1,6 +1,38 @@
|
|||
.text
|
||||
.globl _longjmp
|
||||
_longjmp:
|
||||
jmp __longjmp
|
||||
/ longjmp.gnu.s
|
||||
/
|
||||
/ Created: Oct 15, 1993 by Philip Homburg <philip@cs.vu.nl>
|
||||
|
||||
/ $PchId: longjmp.gnu.s,v 1.4 1996/03/12 19:31:18 philip Exp $
|
||||
.text
|
||||
.globl _longjmp
|
||||
_longjmp:
|
||||
movl 4(%esp), %eax # jmp_buf
|
||||
cmpl $0, 0(%eax) # save mask?
|
||||
je 1f
|
||||
leal 4(%eax), %edx # pointer to sigset_t
|
||||
pushl %edx
|
||||
call ___oldsigset # restore mask
|
||||
addl $4, %esp
|
||||
movl 4(%esp), %eax # jmp_buf
|
||||
1:
|
||||
movl 8(%esp), %ecx # result value
|
||||
movl 12(%eax), %esp # restore stack pointer
|
||||
|
||||
movl 8(%eax), %edx # restore program counter
|
||||
movl %edx, 0(%esp)
|
||||
|
||||
pushl %ecx # save result code
|
||||
|
||||
movl 16(%eax), %ebp # restore frame pointer
|
||||
movl 20(%eax), %ebx
|
||||
movl 24(%eax), %ecx
|
||||
movl 28(%eax), %edx
|
||||
movl 32(%eax), %esi
|
||||
movl 36(%eax), %edi
|
||||
pop %eax
|
||||
testl %eax, %eax
|
||||
jz 1f
|
||||
ret
|
||||
1: movl $1, %eax
|
||||
ret
|
||||
|
||||
/ $PchId: longjmp.gnu.s,v 1.4 1996/03/12 19:30:02 philip Exp $
|
||||
|
|
|
|||
|
|
@ -1,6 +0,0 @@
|
|||
.text
|
||||
.globl _setjmp
|
||||
_setjmp:
|
||||
jmp ___setjmp
|
||||
|
||||
/ $PchId: setjmp.gnu.s,v 1.4 1996/03/12 19:31:18 philip Exp $
|
||||
|
|
@ -1,42 +1,10 @@
|
|||
#include <lib.h>
|
||||
#define sigfillset _sigfillset
|
||||
#define sigjmp _sigjmp
|
||||
#define sigprocmask _sigprocmask
|
||||
#define sigreturn _sigreturn
|
||||
#include <sys/sigcontext.h>
|
||||
#include <setjmp.h>
|
||||
#include <signal.h>
|
||||
|
||||
_PROTOTYPE( int sigjmp, (jmp_buf jb, int retval));
|
||||
|
||||
#if (_SETJMP_SAVES_REGS == 0)
|
||||
/* 'sigreturn' using a short format jmp_buf (no registers saved). */
|
||||
PUBLIC int sigjmp(jb, retval)
|
||||
jmp_buf jb;
|
||||
int retval;
|
||||
{
|
||||
struct sigcontext sc;
|
||||
|
||||
sc.sc_flags = jb[0].__flags;
|
||||
sc.sc_mask = jb[0].__mask;
|
||||
|
||||
#if (CHIP == INTEL)
|
||||
sc.sc_pc = (int) jb[0].__pc;
|
||||
sc.sc_sp = (int) jb[0].__sp;
|
||||
sc.sc_fp = (int) jb[0].__lb;
|
||||
#endif
|
||||
|
||||
#if (CHIP == M68000)
|
||||
sc.sc_pc = (long) jb[0].__pc;
|
||||
sc.sc_sp = (long) jb[0].__sp;
|
||||
sc.sc_fp = (long) jb[0].__lb;
|
||||
#endif
|
||||
|
||||
sc.sc_retreg = retval;
|
||||
return sigreturn(&sc);
|
||||
}
|
||||
#endif
|
||||
|
||||
PUBLIC int sigreturn(scp)
|
||||
register struct sigcontext *scp;
|
||||
{
|
||||
|
|
|
|||
|
|
@ -89,7 +89,6 @@ libc_FILES=" \
|
|||
sigemptyset.s \
|
||||
sigfillset.s \
|
||||
sigismember.s \
|
||||
siglongjmp.s \
|
||||
sigpending.s \
|
||||
sigprocmask.s \
|
||||
sigreturn.s \
|
||||
|
|
|
|||
|
|
@ -1,7 +0,0 @@
|
|||
.sect .text
|
||||
.extern _longjmp
|
||||
.define _siglongjmp
|
||||
.align 2
|
||||
|
||||
_siglongjmp:
|
||||
jmp _longjmp
|
||||
69
man/man3/setjmp.3
Normal file
69
man/man3/setjmp.3
Normal file
|
|
@ -0,0 +1,69 @@
|
|||
.TH SETJMP 3 "June 22, 2006"
|
||||
.UC 4
|
||||
.SH NAME
|
||||
setjmp, longjmp, _setjmp, _longjmp, sigsetjmp, siglongjmp \- save and restore execution contexts
|
||||
.SH SYNOPSIS
|
||||
.nf
|
||||
.ft B
|
||||
#include <setjmp.h>
|
||||
|
||||
int setjmp(jmp_buf env);
|
||||
void longjmp(jmp_buf env, int val);
|
||||
|
||||
int _setjmp(jmp_buf env);
|
||||
void _longjmp(jmp_buf env, int val);
|
||||
|
||||
#define _POSIX_SOURCE
|
||||
int sigsetjmp(sigjmp_buf env, int savemask);
|
||||
void siglongjmp(sigjmp_buf env, int val);
|
||||
.SH DESCRIPTION
|
||||
These calls provide a way for a process to save an execution context into a
|
||||
buffer, and later resume execution from that context, effectively performing
|
||||
a non-local jump. The
|
||||
.B setjmp
|
||||
family of functions store the context into the \fIenv\fP data structure,
|
||||
and return the value 0. The
|
||||
.B longjmp
|
||||
family of functions jump to the context saved in the given \fIenv\fP data
|
||||
structure, causing the process to continue as if it returned from the
|
||||
corresponding
|
||||
.B setjmp
|
||||
call again, but this time with the non-zero return value in \fIval\fP.
|
||||
.PP
|
||||
The difference between the three pairs of setjmp/longjmp functions lies in the
|
||||
behaviour with respect to saving/restoring the process signal mask. POSIX does
|
||||
not require the process signal mask to be saved and restored during
|
||||
.B setjmp
|
||||
/
|
||||
.B longjmp
|
||||
\. However, the current implementation does this in order to agree with OSF/1
|
||||
and other BSD derived systems.
|
||||
.PP
|
||||
The pair of functions
|
||||
.B _setjmp
|
||||
/
|
||||
.B _longjmp
|
||||
, traditional in BSD systems, may be used when the signal mask is not to be
|
||||
saved/restored.
|
||||
.PP
|
||||
Finally, the POSIX
|
||||
.B sigsetjmp
|
||||
/
|
||||
.B siglongjmp
|
||||
functions allow the programmer to specify explicitly whether the signal mask
|
||||
is to be saved/restored, by means of the \fIsavemask\fP parameter. If this
|
||||
parameter is zero, the signal mask will not be saved/restored, otherwise it
|
||||
will.
|
||||
.SH NOTES
|
||||
After the function calling
|
||||
.B setjmp
|
||||
has returned, the saved context may not be used in a call to
|
||||
.B longjmp
|
||||
anymore, since the relevant portion of the stack may already have been wiped
|
||||
out at that point.
|
||||
.PP
|
||||
Using these functions to return to a previous state from a signal handler
|
||||
is possible but should be done with extreme care, as some interrupted library
|
||||
routines may not be reentrant and/or temporarily allocate resources.
|
||||
.PP
|
||||
See the setjmp.h header file for more implementation details specific to Minix.
|
||||
Loading…
Reference in a new issue