88 lines
3.9 KiB
C
88 lines
3.9 KiB
C
/* 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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*
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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 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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* 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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* 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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* As far as porting is concerned --
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*
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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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* 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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* 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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#define _SETJMP_H
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#ifndef _ANSI_H
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#include <ansi.h>
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#endif
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typedef struct {
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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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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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_PROTOTYPE( int __setjmp, (jmp_buf _env, int _savemask) );
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_PROTOTYPE( void longjmp, (jmp_buf _env, int _val) );
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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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#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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#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_H */
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