2 ** OSSP ex - Exception Handling (modified to fit into SimGrid)
3 ** Copyright (c) 2005 Martin Quinson.
4 ** Copyright (c) 2002-2004 Ralf S. Engelschall <rse@engelschall.com>
5 ** Copyright (c) 2002-2004 The OSSP Project <http://www.ossp.org/>
6 ** Copyright (c) 2002-2004 Cable & Wireless <http://www.cw.com/>
8 ** This file is part of OSSP ex, an exception handling library
9 ** which can be found at http://www.ossp.org/pkg/lib/ex/.
11 ** Permission to use, copy, modify, and distribute this software for
12 ** any purpose with or without fee is hereby granted, provided that
13 ** the above copyright notice and this permission notice appear in all
16 ** THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
17 ** WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
18 ** MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19 ** IN NO EVENT SHALL THE AUTHORS AND COPYRIGHT HOLDERS AND THEIR
20 ** CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21 ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22 ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
23 ** USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
24 ** ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
25 ** OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
26 ** OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 ** ex.h: exception handling (pre-processor part)
36 #include <xbt/sysdep.h>
38 /* required ISO-C standard facilities */
41 /* the machine context */
42 #if defined(__EX_MCTX_MCSC__)
43 #include <ucontext.h> /* POSIX.1 ucontext(3) */
44 #define __ex_mctx_struct ucontext_t uc;
45 #define __ex_mctx_save(mctx) (getcontext(&(mctx)->uc) == 0)
46 #define __ex_mctx_restored(mctx) /* noop */
47 #define __ex_mctx_restore(mctx) (void)setcontext(&(mctx)->uc)
49 #elif defined(__EX_MCTX_SSJLJ__)
50 #include <setjmp.h> /* POSIX.1 sigjmp_buf(3) */
51 #define __ex_mctx_struct sigjmp_buf jb;
52 #define __ex_mctx_save(mctx) (sigsetjmp((mctx)->jb, 1) == 0)
53 #define __ex_mctx_restored(mctx) /* noop */
54 #define __ex_mctx_restore(mctx) (void)siglongjmp((mctx)->jb, 1)
56 #elif defined(__EX_MCTX_SJLJ__) || !defined(__EX_MCTX_CUSTOM__)
57 #include <setjmp.h> /* ISO-C jmp_buf(3) */
58 #define __ex_mctx_struct jmp_buf jb;
59 #define __ex_mctx_save(mctx) (setjmp((mctx)->jb) == 0)
60 #define __ex_mctx_restored(mctx) /* noop */
61 #define __ex_mctx_restore(mctx) (void)longjmp((mctx)->jb, 1)
64 /* declare the machine context type */
65 typedef struct { __ex_mctx_struct } __ex_mctx_t;
66 /** @addtogroup XBT_ex
68 * This module is a small ISO-C++ style exception handling library
69 * for use in the ISO-C language. It allows you to use the paradigm
70 * of throwing and catching exceptions in order to reduce the amount
71 * of error handling code without hindering program robustness.
73 * This is achieved by directly transferring exceptional return codes
74 * (and the program control flow) from the location where the exception
75 * is raised (throw point) to the location where it is handled (catch
76 * point) -- usually from a deeply nested sub-routine to a parent
77 * routine. All intermediate routines no longer have to make sure that
78 * the exceptional return codes from sub-routines are correctly passed
81 * These features are brought to you by a modified version of the libex
82 * library, one of the numerous masterpiece of Ralf S. Engelschall.
84 * @section XBT_ex_intro DESCRIPTION
86 * In SimGrid, exceptions is a triple <\a msg , \a category , \a value>
87 * where \a msg is a human-readable text describing the exceptional
88 * condition, \a code an integer describing what went wrong and \a value
89 * providing a sort of sub-category. (this is different in the original libex).
91 * @section XBT_ex_base BASIC USAGE
93 * \em xbt_try \b TRIED_BLOCK [\em xbt_cleanup \b CLEANUP_BLOCK] \em xbt_catch (variable) \b CATCH_BLOCK
95 * This is the primary syntactical construct provided. It is modeled after the
96 * ISO-C++ try-catch clause and should sound familiar to most of you.
98 * Any exception thrown directly from the TRIED_BLOCK block or from called
99 * subroutines is caught. Cleanups which must be done after this block
100 * (whenever an exception arised or not) should be placed into the optionnal
101 * CLEANUP_BLOCK. The code dealing with the exceptions when they arise should
102 * be placed into the (mandatory) CATCH_BLOCK.
105 * In absence of exception, the control flow goes into the blocks TRIED_BLOCK
106 * and CLEANUP_BLOCK (if present); The CATCH_BLOCK block is then ignored.
108 * When an exception is thrown, the control flow goes through the following
109 * blocks: TRIED_BLOCK (up to the statement throwing the exception),
110 * CLEANUP_BLOCK (if any) and CATCH_BLOCK. The exception is stored in a
111 * variable for inspection inside the CATCH_BLOCK. This variable must be
112 * declared in the outter scope, but its value is only valid within the
116 * - xbt_try, xbt_cleanup and xbt_catch cannot be used separately, they work
117 * only in combination and form a language clause as a whole.
118 * - In contrast to the syntax of other languages (such as C++ or Jave) there
119 * is only one xbt_catch block and not multiple ones (all exceptions are
120 * of the same C type xbt_t).
121 * - the variable of xbt_catch can naturally be reused in subsequent
123 * - it is possible to nest xbt_try clauses.
125 * The xbt_try block is a regular ISO-C language statement block, but it is not
126 * allowed to jump into it via "goto" or longjmp(3) or out of it via "break",
127 * "return", "goto" or longjmp(3) because there is some hidden setup and
128 * cleanup that needs to be done regardless of whether an exception is
129 * caught. Bypassing these steps will break the exception handling facility.
131 * The xbt_cleanup and xbt_catch blocks are regular ISO-C language statement
132 * blocks without any restrictions. You are even allowed to throw (and in the
133 * xbt_catch block to re-throw) exceptions.
135 * There is one subtle detail you should remember about xbt_try blocks:
136 * Variables used in the xbt_cleanup or xbt_catch clauses must be declared with
137 * the storage class "volatile", otherwise they might contain outdated
138 * information if an exception it thrown.
141 * This is because you usually do not know which commands in the xbt_try
142 * were already successful before the exception was thrown (logically speaking)
143 * and because the underlying ISO-C setjmp(3) facility applies those
144 * restrictions (technically speaking). As a matter of fact, value changes
145 * between the xbt_try and the xbt_throw may be discarded if you forget the
146 * "volatile" keyword.
148 * @section XBT_ex_advanced ADVANCED USAGE
150 * @subsection xbt_defer DEFERING_BLOCK XBT_ex_defer
152 * This directive executes DEFERING_BLOCK while deferring the throwing of
153 * exceptions, i.e., exceptions thrown within this block are remembered, but
154 * the control flow still continues until the end of the block. At its end, the
155 * first exception which occured within the block (if any) is rethrown (any
156 * subsequent exceptions are ignored).
158 * DEFERING_BLOCK is a regular ISO-C language statement block, but it is not
159 * allowed to jump into it via "goto" or longjmp(3) or out of it via "break",
160 * "return", "goto" or longjmp(3). It is however allowed to nest xbt_defer
163 * @subsection XBT_ex_shield xbt_shield SHIELDED_BLOCK
165 * This directive executes SHIELDED_BLOCK while shielding it against the
166 * throwing of exceptions, i.e., any exception thrown from this block or its
167 * subroutines are silently ignored.
169 * SHIELDED_BLOCK is a regular ISO-C language statement block, but it is not
170 * allowed to jump into it via "goto" or longjmp(3) or out of it via "break",
171 * "return", "goto" or longjmp(3). It is however allowed to nest xbt_shield
174 * @subsection XBT_ex_conditions Retrieving the current execution condition
176 * \a xbt_catching, \a xbt_deferred and \a xbt_shielding return a boolean
177 * indicating whether the current scope is within a TRYIED_BLOCK,
178 * DEFERING_BLOCK and SHIELDED_BLOCK (respectively)
180 * \section XBT_ex_pitfalls PROGRAMMING PITFALLS
182 * Exception handling is a very elegant and efficient way of dealing with
183 * exceptional situation. Nevertheless it requires additional discipline in
184 * programming and there are a few pitfalls one must be aware of. Look the
185 * following code which shows some pitfalls and contains many errors (assuming
186 * a mallocex() function which throws an exception if malloc(3) fails):
188 * \dontinclude ex_test.c
190 * \until end_of_bad_example
192 * This example raises a few issues:
193 * -# \b variable \b scope \n
194 * Variables which are used in the xbt_cleanup or xbt_catch clauses must be
195 * declared before the xbt_try clause, otherwise they only exist inside the
196 * xbt_try block. In the example above, cp1, cp2 and cp3 only exist in the
197 * xbt_try block and are invisible from the xbt_cleanup and xbt_catch
199 * -# \b variable \b initialization \n
200 * Variables which are used in the xbt_cleanup or xbt_catch clauses must
201 * be initialized before the point of the first possible xbt_throw is
202 * reached. In the example above, xbt_cleanup would have trouble using cp3
203 * if mallocex() throws a exception when allocating a TOOBIG buffer.
204 * -# \b volatile \b variable \n
205 * Variables which are used in the xbt_cleanup or xbt_catch clauses MUST BE
206 * DECLARED AS "volatile", otherwise they might contain outdated
207 * information when an exception is thrown.
208 * -# \b clean \b before \b catch \n
209 * The xbt_cleanup clause is not only place before the xbt_catch clause in
210 * the source code, it also occures before in the control flow. So,
211 * resources being cleaned up cannot be used in the xbt_catch block. In the
212 * example, c3 gets freed before the printf placed in xbt_catch.
213 * -# \b variable \b uninitialization \n
214 * If resources are passed out of the scope of the
215 * xbt_try/xbt_cleanup/xbt_catch construct, they naturally shouldn't get
216 * cleaned up. The example above does free(3) cp1 in xbt_cleanup although
217 * its value was affected to globalcontext->first, invalidating this
220 * The following is fixed version of the code (annotated with the pitfall items
224 * \until end_of_good_example
229 /** @brief Structure describing an exception */
231 char *msg; /**< human readable message; to be freed */
232 int category; /**< category like HTTP (what went wrong) */
233 int value; /**< like errno (why did it went wrong) */
235 char *host; /* NULL for localhost; hostname:port if remote */
237 char *file; /**< to be freed only for remote exceptions */
239 char *func; /**< to be freed only for remote exceptions */
242 /* declare the context type (private) */
244 __ex_mctx_t *ctx_mctx; /* permanent machine context of enclosing try/catch */
245 int ctx_deferred; /* permanent flag whether exception is deferred */
246 int ctx_deferring;/* permanent counter of exception deferring level */
247 int ctx_defer; /* temporary flag for exception deferring macro */
248 int ctx_shielding;/* permanent counter of exception shielding level */
249 int ctx_shield; /* temporary flag for exception shielding macro */
250 int ctx_caught; /* temporary flag whether exception was caught */
251 volatile ex_t ctx_ex; /* temporary exception storage */
254 /* the static and dynamic initializers for a context structure */
255 #define XBT_CTX_INITIALIZER \
256 { NULL, 0, 0, 0, 0, 0, 0, { /* content */ NULL, 0, 0, \
257 /*throw point*/ NULL, NULL, NULL, 0, NULL } }
258 #define XBT_CTX_INITIALIZE(ctx) \
260 (ctx)->ctx_mctx = NULL; \
261 (ctx)->ctx_deferred = 0; \
262 (ctx)->ctx_deferring = 0; \
263 (ctx)->ctx_defer = 0; \
264 (ctx)->ctx_shielding = 0; \
265 (ctx)->ctx_shield = 0; \
266 (ctx)->ctx_caught = 0; \
267 (ctx)->ctx_ex.msg = NULL; \
268 (ctx)->ctx_ex.category = 0; \
269 (ctx)->ctx_ex.value = 0; \
270 (ctx)->ctx_ex.host = NULL; \
271 (ctx)->ctx_ex.procname = NULL; \
272 (ctx)->ctx_ex.file = NULL; \
273 (ctx)->ctx_ex.line = 0; \
274 (ctx)->ctx_ex.func = NULL; \
277 /* the exception context */
278 typedef ex_ctx_t *(*ex_ctx_cb_t)(void);
279 extern ex_ctx_cb_t __xbt_ex_ctx;
280 extern ex_ctx_t *__xbt_ex_ctx_default(void);
282 /* the termination handler */
283 typedef void (*ex_term_cb_t)(ex_t *);
284 extern ex_term_cb_t __xbt_ex_terminate;
285 extern void __xbt_ex_terminate_default(ex_t *e);
287 /** @brief Introduce a block where exception may be dealed with
292 ex_ctx_t *__xbt_ex_ctx_ptr = __xbt_ex_ctx(); \
293 int __ex_cleanup = 0; \
294 __ex_mctx_t *__ex_mctx_en; \
295 __ex_mctx_t __ex_mctx_me; \
296 __ex_mctx_en = __xbt_ex_ctx_ptr->ctx_mctx; \
297 __xbt_ex_ctx_ptr->ctx_mctx = &__ex_mctx_me; \
298 if (__ex_mctx_save(&__ex_mctx_me)) { \
301 /** @brief optional(!) block for cleanup
304 #define xbt_cleanup \
307 __xbt_ex_ctx_ptr->ctx_caught = 0; \
310 __ex_mctx_restored(&__ex_mctx_me); \
311 __xbt_ex_ctx_ptr->ctx_caught = 1; \
313 __xbt_ex_ctx_ptr->ctx_mctx = __ex_mctx_en; \
318 /** @brief the block for catching (ie, deal with) an exception
321 #define xbt_catch(e) \
324 if (!(__ex_cleanup)) \
325 __xbt_ex_ctx_ptr->ctx_caught = 0; \
328 if (!(__ex_cleanup)) { \
329 __ex_mctx_restored(&__ex_mctx_me); \
330 __xbt_ex_ctx_ptr->ctx_caught = 1; \
333 __xbt_ex_ctx_ptr->ctx_mctx = __ex_mctx_en; \
335 if ( !(__xbt_ex_ctx()->ctx_caught) \
336 || ((e) = __xbt_ex_ctx()->ctx_ex, 0)) { \
340 /** @brief Build an exception from the supplied arguments and throws it
343 * @param c: category code (integer)
344 * @param v: value (integer)
345 * @param m: message text
347 * If called from within a sg_try/sg_catch construct, this exception
348 * is copied into the sg_catch relevant variable program control flow
349 * is derouted to the sg_catch (after the optional sg_cleanup).
351 * If no sg_try/sg_catch conctruct embeeds this call, the program calls
354 * The sg_throw can be performed everywhere, including inside sg_try,
355 * sg_cleanup and sg_catch blocks.
357 #define xbt_throw(c,v,m) \
358 (( __xbt_ex_ctx()->ctx_shielding > 0 \
359 || (__xbt_ex_ctx()->ctx_deferring > 0 && __xbt_ex_ctx()->ctx_deferred == 1)) ? 0 : \
360 (__xbt_ex_ctx()->ctx_ex.msg = bprintf(m), \
361 __xbt_ex_ctx()->ctx_ex.category = (c), \
362 __xbt_ex_ctx()->ctx_ex.value = (v), \
363 __xbt_ex_ctx()->ctx_ex.host = (char*)NULL, \
364 __xbt_ex_ctx()->ctx_ex.procname = strdup(xbt_procname()), \
365 __xbt_ex_ctx()->ctx_ex.file = (char*)__FILE__, \
366 __xbt_ex_ctx()->ctx_ex.line = __LINE__, \
367 __xbt_ex_ctx()->ctx_ex.func = (char*)_XBT_FUNCTION, \
368 __xbt_ex_ctx()->ctx_deferred = 1, \
369 (__xbt_ex_ctx()->ctx_deferring > 0 ? 0 : \
370 (__xbt_ex_ctx()->ctx_mctx == NULL \
371 ? (__xbt_ex_terminate((ex_t *)&(__xbt_ex_ctx()->ctx_ex)), -1) \
372 : (__ex_mctx_restore(__xbt_ex_ctx()->ctx_mctx), 1) ))))
374 /** @brief re-throwing of an already caught exception (ie, pass it to the upper catch block)
377 #define xbt_rethrow \
378 (( __xbt_ex_ctx()->ctx_shielding > 0 \
379 || __xbt_ex_ctx()->ctx_deferring > 0) ? 0 : \
380 ( __xbt_ex_ctx()->ctx_mctx == NULL \
381 ? (__xbt_ex_terminate((ex_t *)&(__xbt_ex_ctx()->ctx_ex)), -1) \
382 : (__ex_mctx_restore(__xbt_ex_ctx()->ctx_mctx), 1) ))
384 /** @brief shield an operation from exception handling
388 for (__xbt_ex_ctx()->ctx_shielding++, \
389 __xbt_ex_ctx()->ctx_shield = 1; \
390 __xbt_ex_ctx()->ctx_shield == 1; \
391 __xbt_ex_ctx()->ctx_shield = 0, \
392 __xbt_ex_ctx()->ctx_shielding--)
394 /** @brief defer immediate exception handling
398 for (((__xbt_ex_ctx()->ctx_deferring)++ == 0 ? __xbt_ex_ctx()->ctx_deferred = 0 : 0), \
399 __xbt_ex_ctx()->ctx_defer = 1; \
400 __xbt_ex_ctx()->ctx_defer == 1; \
401 __xbt_ex_ctx()->ctx_defer = 0, \
402 ((--(__xbt_ex_ctx()->ctx_deferring) == 0 && __xbt_ex_ctx()->ctx_deferred == 1) ? xbt_rethrow : 0))
404 /** @brief exception handling tests
407 #define xbt_catching \
408 (__xbt_ex_ctx()->ctx_mctx != NULL)
409 /** @brief exception handling tests
412 #define xbt_shielding \
413 (__xbt_ex_ctx()->ctx_shielding > 0)
414 /** @brief exception handling tests
417 #define xbt_deferring \
418 (__xbt_ex_ctx()->ctx_deferring > 0)
420 /* optional namespace mapping */
421 #if defined(__EX_NS_UCCXX__)
423 #define Cleanup xbt_cleanup
424 #define Catch xbt_catch
425 #define Throw xbt_throw
426 #define Rethrow xbt_rethrow
427 #define Shield xbt_shield
428 #define Defer xbt_defer
429 #elif defined(__EX_NS_CXX__) || (!defined(__cplusplus) && !defined(__EX_NS_CUSTOM__))
431 #define cleanup xbt_cleanup
432 #define catch xbt_catch
433 #define throw xbt_throw
434 #define rethrow xbt_rethrow
435 #define shield xbt_shield
436 #define defer xbt_defer
440 #endif /* __XBT_EX_H__ */