AVR Libc Home Page |  | AVR Libc Development Pages
Main Page | User Manual | Library Reference | FAQ | Alphabetical Index | Example Projects

setjmp.h
Go to the documentation of this file.
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.h 1656 2008-03-24 11:29:55Z dmix $ */
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 call-saved registers (r2-r17)
44 16 2 frame pointer (r29:r28)
45 18 2 stack pointer (SPH:SPL)
46 20 1 status register (SREG)
47 21 2/3 return address (PC) (2 bytes used for <=128Kw flash)
48 23/24 = total size
49 */
50
51 #if !defined(__DOXYGEN__)
52
53 #if defined(__AVR_3_BYTE_PC__) && __AVR_3_BYTE_PC__
54 # define _JBLEN 24
55 #else
56 # define _JBLEN 23
57 #endif
58 typedef struct _jmp_buf { unsigned char _jb[_JBLEN]; } jmp_buf[1];
59
60 #endif /* not __DOXYGEN__ */
61
62 /** \file */
63 /** \defgroup setjmp <setjmp.h>: Non-local goto
64
65 While the C language has the dreaded \c goto statement, it can only be
66 used to jump to a label in the same (local) function. In order to jump
67 directly to another (non-local) function, the C library provides the
68 setjmp() and longjmp() functions. setjmp() and longjmp() are useful for
69 dealing with errors and interrupts encountered in a low-level subroutine
70 of a program.
71
72 \note setjmp() and longjmp() make programs hard to understand and maintain.
73 If possible, an alternative should be used.
74
75 \note longjmp() can destroy changes made to global register
76 variables (see \ref faq_regbind).
77
78 For a very detailed discussion of setjmp()/longjmp(), see Chapter 7 of
79 <em>Advanced Programming in the UNIX Environment</em>, by W. Richard
80 Stevens.
81
82 Example:
83
84 \code
85 #include <setjmp.h>
86
87 jmp_buf env;
88
89 int main (void)
90 {
91 if (setjmp (env))
92 {
93 ... handle error ...
94 }
95
96 while (1)
97 {
98 ... main processing loop which calls foo() some where ...
99 }
100 }
101
102 ...
103
104 void foo (void)
105 {
106 ... blah, blah, blah ...
107
108 if (err)
109 {
110 longjmp (env, 1);
111 }
112 }
113 \endcode */
114
115 #ifndef __ATTR_NORETURN__
116 #define __ATTR_NORETURN__ __attribute__((__noreturn__))
117 #endif
118
119 /** \ingroup setjmp
120 \brief Save stack context for non-local goto.
121
122 \code #include <setjmp.h>\endcode
123
124 setjmp() saves the stack context/environment in \e __jmpb for later use by
125 longjmp(). The stack context will be invalidated if the function which
126 called setjmp() returns.
127
128 \param __jmpb Variable of type \c jmp_buf which holds the stack
129 information such that the environment can be restored.
130
131 \returns setjmp() returns 0 if returning directly, and
132 non-zero when returning from longjmp() using the saved context. */
133
134 extern int setjmp(jmp_buf __jmpb);
135
136 /** \ingroup setjmp
137 \brief Non-local jump to a saved stack context.
138
139 \code #include <setjmp.h>\endcode
140
141 longjmp() restores the environment saved by the last call of setjmp() with
142 the corresponding \e __jmpb argument. After longjmp() is completed,
143 program execution continues as if the corresponding call of setjmp() had
144 just returned the value \e __ret.
145
146 \note longjmp() cannot cause 0 to be returned. If longjmp() is invoked
147 with a second argument of 0, 1 will be returned instead.
148
149 \param __jmpb Information saved by a previous call to setjmp().
150 \param __ret Value to return to the caller of setjmp().
151
152 \returns This function never returns. */
153
154 extern void longjmp(jmp_buf __jmpb, int __ret) __ATTR_NORETURN__;
155
156 #ifdef __cplusplus
157 }
158 #endif
159
160 #endif /* !__SETJMP_H_ */

Automatically generated by Doxygen 1.8.3.1 on Sat Jun 22 2013.