avr-libc  2.0.0
Standard C library for AVR-GCC

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setjmp.h
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1 /* Copyright (c) 2002,2007 Marek Michalkiewicz
2  All rights reserved.
3 
4  Redistribution and use in source and binary forms, with or without
5  modification, are permitted provided that the following conditions are met:
6 
7  * Redistributions of source code must retain the above copyright
8  notice, this list of conditions and the following disclaimer.
9 
10  * Redistributions in binary form must reproduce the above copyright
11  notice, this list of conditions and the following disclaimer in
12  the documentation and/or other materials provided with the
13  distribution.
14 
15  * Neither the name of the copyright holders nor the names of
16  contributors may be used to endorse or promote products derived
17  from this software without specific prior written permission.
18 
19  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
20  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
23  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29  POSSIBILITY OF SUCH DAMAGE. */
30 
31 /* $Id: setjmp_8h_source.html,v 1.1.1.6 2016/02/09 07:13:52 joerg_wunsch Exp $ */
32 
33 #ifndef __SETJMP_H_
34 #define __SETJMP_H_ 1
35 
36 #ifdef __cplusplus
37 extern "C" {
38 #endif
39 
40 /*
41  jmp_buf:
42  offset size description
43  0 16/2 call-saved registers (r2-r17)
44  (AVR_TINY arch has only 2 call saved registers (r18,r19))
45  16/2 2 frame pointer (r29:r28)
46  18/4 2 stack pointer (SPH:SPL)
47  20/6 1 status register (SREG)
48  21/7 2/3 return address (PC) (2 bytes used for <=128Kw flash)
49  23/24/9 = total size (AVR_TINY arch always has 2 bytes PC)
50  */
51 
52 #if !defined(__DOXYGEN__)
53 
54 #if defined(__AVR_TINY__)
55 # define _JBLEN 9
56 #elif defined(__AVR_3_BYTE_PC__) && __AVR_3_BYTE_PC__
57 # define _JBLEN 24
58 #else
59 # define _JBLEN 23
60 #endif
61 typedef struct _jmp_buf { unsigned char _jb[_JBLEN]; } jmp_buf[1];
62 
63 #endif /* not __DOXYGEN__ */
64 
65 /** \file */
66 /** \defgroup setjmp <setjmp.h>: Non-local goto
67 
68  While the C language has the dreaded \c goto statement, it can only be
69  used to jump to a label in the same (local) function. In order to jump
70  directly to another (non-local) function, the C library provides the
71  setjmp() and longjmp() functions. setjmp() and longjmp() are useful for
72  dealing with errors and interrupts encountered in a low-level subroutine
73  of a program.
74 
75  \note setjmp() and longjmp() make programs hard to understand and maintain.
76  If possible, an alternative should be used.
77 
78  \note longjmp() can destroy changes made to global register
79  variables (see \ref faq_regbind).
80 
81  For a very detailed discussion of setjmp()/longjmp(), see Chapter 7 of
82  <em>Advanced Programming in the UNIX Environment</em>, by W. Richard
83  Stevens.
84 
85  Example:
86 
87  \code
88  #include <setjmp.h>
89 
90  jmp_buf env;
91 
92  int main (void)
93  {
94  if (setjmp (env))
95  {
96  ... handle error ...
97  }
98 
99  while (1)
100  {
101  ... main processing loop which calls foo() some where ...
102  }
103  }
104 
105  ...
106 
107  void foo (void)
108  {
109  ... blah, blah, blah ...
110 
111  if (err)
112  {
113  longjmp (env, 1);
114  }
115  }
116  \endcode */
117 
118 #if !(defined(__ATTR_NORETURN__) || defined(__DOXYGEN__))
119 #define __ATTR_NORETURN__ __attribute__((__noreturn__))
120 #endif
121 
122 /** \ingroup setjmp
123  \brief Save stack context for non-local goto.
124 
125  \code #include <setjmp.h>\endcode
126 
127  setjmp() saves the stack context/environment in \e __jmpb for later use by
128  longjmp(). The stack context will be invalidated if the function which
129  called setjmp() returns.
130 
131  \param __jmpb Variable of type \c jmp_buf which holds the stack
132  information such that the environment can be restored.
133 
134  \returns setjmp() returns 0 if returning directly, and
135  non-zero when returning from longjmp() using the saved context. */
136 
137 extern int setjmp(jmp_buf __jmpb);
138 
139 /** \ingroup setjmp
140  \brief Non-local jump to a saved stack context.
141 
142  \code #include <setjmp.h>\endcode
143 
144  longjmp() restores the environment saved by the last call of setjmp() with
145  the corresponding \e __jmpb argument. After longjmp() is completed,
146  program execution continues as if the corresponding call of setjmp() had
147  just returned the value \e __ret.
148 
149  \note longjmp() cannot cause 0 to be returned. If longjmp() is invoked
150  with a second argument of 0, 1 will be returned instead.
151 
152  \param __jmpb Information saved by a previous call to setjmp().
153  \param __ret Value to return to the caller of setjmp().
154 
155  \returns This function never returns. */
156 
157 extern void longjmp(jmp_buf __jmpb, int __ret) __ATTR_NORETURN__;
158 
159 #ifdef __cplusplus
160 }
161 #endif
162 
163 #endif /* !__SETJMP_H_ */
int setjmp(jmp_buf __jmpb)
Save stack context for non-local goto.
void longjmp(jmp_buf __jmpb, int __ret) __ATTR_NORETURN__
Non-local jump to a saved stack context.