# setjmp.h

/* Copyright (c) 2002,2007 Marek Michalkiewicz

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      16/4    call-saved registers (r2-r17)
(AVR tiny10 family has only 4 call saved registers (r18-r21))
16/4     2      frame pointer (r29:r28)
18/6     2      stack pointer (SPH:SPL)
20/8     1      status register (SREG)
21/9     2/3    return address (PC) (2 bytes used for <=128Kw flash)
23/24/11 = total size (AVR Tiny10 family always has 2 bytes PC)
*/

#if !defined(__DOXYGEN__)

#if defined(__AVR_TINY__)
# define _JBLEN 11
#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() some where ...
}
}

...

void foo (void)
{
... blah, blah, blah ...

if (err)
{
longjmp (env, 1);
}
}
\endcode */

#ifndef __ATTR_NORETURN__
#define __ATTR_NORETURN__ __attribute__((__noreturn__))
#endif

/** \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

\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().