minix/include/setjmp.h
2011-01-28 11:35:02 +00:00

88 lines
3.9 KiB
C

/* The <setjmp.h> header relates to the C phenomenon known as setjmp/longjmp.
* It is used to escape out of the current situation into a previous one.
*
* The actual implementations of all these functions and, by extension, parts
* of this header, are both compiler- and architecture-dependent. Currently
* two compilers are supported: ACK and GCC. Each of these has their own
* implementation of the functions in their runtime system library code.
* As it is impossible to predict the requirements for any other compilers,
* this header may not be compatible with such other compilers either.
*
* The ACK compiler will not enregister any variables inside a function
* containing a setjmp call, even if those variables are explicitly declared
* as register variables. Thus for ACK, of all the registers, only the
* program counter, stack pointer and frame pointer have to be saved into the
* jmp_buf structure. This makes the jmp_buf structure very small, and
* moreover, the implementation of the setjmp/longjmp calls (written in EM)
* architecture-independent and thus very portable. The ACK compiler
* recognizes only the symbol __setjmp as being such a setjmp call.
*
* The GCC compiler recognizes all of the setjmp/_setjmp/__setjmp name
* variants as calls to setjmp functions, and treats them as special
* accordingly, but does require that the setjmp implementation save and
* restore most of the registers. It has no portable setjmp and longjmp
* functions like ACK, and therefore has to have enough space in the jmp_buf
* structure to store the registers on any architecture it's ported to.
*
* Taking the common denominator of both compilers, the function definitions
* in this header rely on the presence of merely two functions: __setjmp and
* longjmp. On the other hand, the size of jmp_buf depends on the compiler
* used: for ACK, jmp_buf is exactly big enough to store the three mentioned
* registers; for GCC and any other compiler, the size is chosen in such a
* way that it's likely to offer enough room to store registers for any
* architecture. The POSIX sigjmp_buf is identical to jmp_buf in all cases.
*
* As far as porting is concerned --
*
* All code writers/porters that have to deal with the actual contents of the
* jmp_buf structure in one way or another, should look at <sys/jmp_buf.h>.
*
* Porters of a new compiler to Minix have to make sure the compiler
* recognizes at least __setjmp as a setjmp call (if applicable) and provide
* library implementations of __setjmp and longjmp conforming to their
* declarations below; if this is not possible, compiler-specific code will
* have to be added to this header.
*
* Porters of Minix+GCC to other architectures have to make sure that the
* __regs array of the jmp_buf structure is large enough to hold all the
* registers the __setjmp implementation for that architecture has to save.
*/
#ifndef _SETJMP_H
#define _SETJMP_H
#ifndef _MINIX_ANSI_H
#include <minix/ansi.h>
#endif
typedef struct {
#if defined(__ACK__)
_PROTOTYPE(void (*__pc),(void)); /* program counter */
void *__sp; /* stack pointer */
void *__lb; /* local base (ACKspeak for frame pointer) */
long __mask; /* must have size >= sizeof(sigset_t) */
int __flags;
#else /* GCC */
int __flags; /* XXX - long might give better alignment */
long __mask; /* must have size >= sizeof(sigset_t) */
void *__regs[16]; /* actual use is architecture dependent */
#endif
} jmp_buf[1];
_PROTOTYPE( int __setjmp, (jmp_buf _env, int _savemask) );
_PROTOTYPE( void longjmp, (jmp_buf _env, int _val) );
#define setjmp(env) __setjmp((env), 1)
#ifdef _MINIX
#define _setjmp(env) __setjmp((env), 0)
#define _longjmp(env, val) longjmp((env), (val))
#endif
#ifdef _POSIX_SOURCE
typedef jmp_buf sigjmp_buf;
#define sigsetjmp(env, savemask) __setjmp((env), (savemask))
#define siglongjmp(env, val) longjmp((env), (val))
#endif /* _POSIX_SOURCE */
#endif /* _SETJMP_H */