setjmp.h

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/* Copyright (c) 2002,2007 Marek Michalkiewicz
   All rights reserved.
 
   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions are met:
 
   * Redistributions of source code must retain the above copyright
     notice, this list of conditions and the following disclaimer.
 
   * Redistributions in binary form must reproduce the above copyright
     notice, this list of conditions and the following disclaimer in
     the documentation and/or other materials provided with the
     distribution.
 
   * Neither the name of the copyright holders nor the names of
     contributors may be used to endorse or promote products derived
     from this software without specific prior written permission.
 
  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  POSSIBILITY OF SUCH DAMAGE. */
 
/* $Id$ */
 
#ifndef __SETJMP_H_
#define __SETJMP_H_ 1
 
#ifdef __cplusplus
extern "C" {
#endif
 
/*
   jmp_buf:
    offset  size    description
     0  16/2    call-saved registers (r2-r17)
                (AVR_TINY arch has only 2 call saved registers (r18,r19))
    16/2     2  frame pointer (r29:r28)
    18/4     2  stack pointer (SPH:SPL)
    20/6     1  status register (SREG)
    21/7     2/3    return address (PC) (2 bytes used for <=128Kw flash)
    23/24/9 = total size (AVR_TINY arch always has 2 bytes PC)
 */
 
#if !defined(__DOXYGEN__)
 
#if defined(__AVR_TINY__)
# define _JBLEN  9
#elif   defined(__AVR_3_BYTE_PC__) && __AVR_3_BYTE_PC__
# define _JBLEN  24
#else
# define _JBLEN  23
#endif
typedef struct _jmp_buf { unsigned char _jb[_JBLEN]; } jmp_buf[1];
 
#endif /* not __DOXYGEN__ */
 
/** \file */
/** \defgroup setjmp <setjmp.h>: Non-local goto
 
    While the C language has the dreaded \c goto statement, it can only be
    used to jump to a label in the same (local) function.  In order to jump
    directly to another (non-local) function, the C library provides the
    #setjmp and #longjmp functions.  setjmp and longjmp are useful for
    dealing with errors and interrupts encountered in a low-level subroutine
    of a program.
 
    \note #setjmp and #longjmp make programs hard to understand and maintain.
    If possible, an alternative should be used.
 
    \note longjmp can destroy changes made to global register
    variables (see \ref faq_regbind).
 
    For a very detailed discussion of setjmp/longjmp, see Chapter 7 of
    <em>Advanced Programming in the UNIX Environment</em>, by W. Richard
    Stevens.
 
    Example:
 
    \code
    #include <setjmp.h>
 
    jmp_buf env;
 
    int main (void)
    {
        if (setjmp (env))
        {
            // Handle error ...
        }
 
        while (1)
        {
           // Main processing loop which calls foo() somewhere ...
        }
    }
 
    void foo (void)
    {
        // blah, blah, blah ...
 
        if (err)
        {
            longjmp (env, 1);
        }
    }
    \endcode */
 
#ifndef __DOXYGEN__
#ifndef __ATTR_NORETURN__
#define __ATTR_NORETURN__ __attribute__((__noreturn__))
#endif
#endif /* ! DOXYGEN */
 
/** \ingroup setjmp
    \brief Save stack context for non-local goto.
 
    \code #include <setjmp.h>\endcode
 
    setjmp() saves the stack context/environment in \e __jmpb for later use by
    longjmp().  The stack context will be invalidated if the function which
    called setjmp() returns.
 
    \param __jmpb Variable of type \c jmp_buf which holds the stack
    information such that the environment can be restored.
 
    \returns setjmp() returns 0 if returning directly, and
    non-zero when returning from longjmp() using the saved context. */
 
extern int setjmp(jmp_buf __jmpb);
 
/** \ingroup setjmp
    \brief Non-local jump to a saved stack context.
 
    \code #include <setjmp.h>\endcode
 
    longjmp() restores the environment saved by the last call of setjmp() with
    the corresponding \e __jmpb argument.  After longjmp() is completed,
    program execution continues as if the corresponding call of setjmp() had
    just returned the value \e __ret.
 
    \note longjmp() cannot cause 0 to be returned.  If longjmp() is invoked
    with a second argument of 0, 1 will be returned instead.
 
    \param __jmpb Information saved by a previous call to setjmp().
    \param __ret  Value to return to the caller of setjmp().
 
    \returns This function never returns. */
 
extern void longjmp(jmp_buf __jmpb, int __ret) __ATTR_NORETURN__;
 
#ifdef __cplusplus
}
#endif
 
#endif  /* !__SETJMP_H_ */