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;
69 * This module is a small ISO-C++ style exception handling library
70 * for use in the ISO-C language. It allows you to use the paradigm
71 * of throwing and catching exceptions in order to reduce the amount
72 * of error handling code without hindering program robustness.
74 * This is achieved by directly transferring exceptional return codes
75 * (and the program control flow) from the location where the exception
76 * is raised (throw point) to the location where it is handled (catch
77 * point) -- usually from a deeply nested sub-routine to a parent
78 * routine. All intermediate routines no longer have to make sure that
79 * the exceptional return codes from sub-routines are correctly passed
82 * These features are brought to you by a modified version of the libex
83 * library, one of the numerous masterpiece of Ralf S. Engelschall.
85 * @section Introduction
87 * In SimGrid, exceptions is a triple <\a msg , \a category , \a value>
88 * where \a msg is a human-readable text describing the exceptional
89 * condition, \a code an integer describing what went wrong and \a value
90 * providing a sort of sub-category. (this is different in the original libex).
92 * @section Basic usage
94 * \em xbt_try \b TRIED_BLOCK [\em xbt_cleanup \b CLEANUP_BLOCK] \em xbt_catch (variable) \b CATCH_BLOCK
96 * This is the primary syntactical construct provided. It is modeled after the
97 * ISO-C++ try-catch clause and should sound familiar to most of you.
99 * Any exception thrown directly from the TRIED_BLOCK block or from called
100 * subroutines is caught. Cleanups which must be done after this block
101 * (whenever an exception arised or not) should be placed into the optionnal
102 * CLEANUP_BLOCK. The code dealing with the exceptions when they arise should
103 * be placed into the (mandatory) CATCH_BLOCK.
106 * In absence of exception, the control flow goes into the blocks TRIED_BLOCK
107 * and CLEANUP_BLOCK (if present); The CATCH_BLOCK block is then ignored.
109 * When an exception is thrown, the control flow goes through the following
110 * blocks: TRIED_BLOCK (up to the statement throwing the exception),
111 * CLEANUP_BLOCK (if any) and CATCH_BLOCK. The exception is stored in a
112 * variable for inspection inside the CATCH_BLOCK. This variable must be
113 * declared in the outter scope, but its value is only valid within the
117 * - xbt_try, xbt_cleanup and xbt_catch cannot be used separately, they work
118 * only in combination and form a language clause as a whole.
119 * - In contrast to the syntax of other languages (such as C++ or Jave) there
120 * is only one xbt_catch block and not multiple ones (all exceptions are
121 * of the same C type xbt_t).
122 * - the variable of xbt_catch can naturally be reused in subsequent
124 * - it is possible to nest xbt_try clauses.
126 * The xbt_try block is a regular ISO-C language statement block, but it is not
127 * allowed to jump into it via "goto" or longjmp(3) or out of it via "break",
128 * "return", "goto" or longjmp(3) because there is some hidden setup and
129 * cleanup that needs to be done regardless of whether an exception is
130 * caught. Bypassing these steps will break the exception handling facility.
132 * The xbt_cleanup and xbt_catch blocks are regular ISO-C language statement
133 * blocks without any restrictions. You are even allowed to throw (and in the
134 * xbt_catch block to re-throw) exceptions.
136 * There is one subtle detail you should remember about xbt_try blocks:
137 * Variables used in the xbt_cleanup or xbt_catch clauses must be declared with
138 * the storage class "volatile", otherwise they might contain outdated
139 * information if an exception it thrown.
142 * This is because you usually do not know which commands in the xbt_try
143 * were already successful before the exception was thrown (logically speaking)
144 * and because the underlying ISO-C setjmp(3) facility applies those
145 * restrictions (technically speaking). As a matter of fact, value changes
146 * between the xbt_try and the xbt_throw may be discarded if you forget the
147 * "volatile" keyword.
149 * @section Advanced usage
151 * @subsection xbt_defer DEFERING_BLOCK
153 * This directive executes DEFERING_BLOCK while deferring the throwing of
154 * exceptions, i.e., exceptions thrown within this block are remembered, but
155 * the control flow still continues until the end of the block. At its end, the
156 * first exception which occured within the block (if any) is rethrown (any
157 * subsequent exceptions are ignored).
159 * DEFERING_BLOCK is a regular ISO-C language statement block, but it is not
160 * allowed to jump into it via "goto" or longjmp(3) or out of it via "break",
161 * "return", "goto" or longjmp(3). It is however allowed to nest xbt_defer
164 * @subsection xbt_shield SHIELDED_BLOCK
166 * This directive executes SHIELDED_BLOCK while shielding it against the
167 * throwing of exceptions, i.e., any exception thrown from this block or its
168 * subroutines are silently ignored.
170 * SHIELDED_BLOCK is a regular ISO-C language statement block, but it is not
171 * allowed to jump into it via "goto" or longjmp(3) or out of it via "break",
172 * "return", "goto" or longjmp(3). It is however allowed to nest xbt_shield
175 * @subsection Retrieving the current execution condition
177 * \a xbt_catching, \a xbt_deferred and \a xbt_shielding return a boolean
178 * indicating whether the current scope is within a TRYIED_BLOCK,
179 * DEFERING_BLOCK and SHIELDED_BLOCK (respectively)
181 * \section PROGRAMMING PITFALLS
183 * Exception handling is a very elegant and efficient way of dealing with
184 * exceptional situation. Nevertheless it requires additional discipline in
185 * programming and there are a few pitfalls one must be aware of. Look the
186 * following code which shows some pitfalls and contains many errors (assuming
187 * a mallocex() function which throws an exception if malloc(3) fails):
192 char *cp1, *cp2, cp3;
194 cp1 = mallocex(SMALLAMOUNT);
195 globalcontext->first = cp1;
196 cp2 = mallocex(TOOBIG);
197 cp3 = mallocex(SMALLAMOUNT);
201 if (cp3 != NULL) free(cp3);
202 if (cp2 != NULL) free(cp2);
203 if (cp1 != NULL) free(cp1);
205 printf("cp3=%s", cp3);
209 * This example raises a few issues:
210 * -# \b variable scope\n
211 * Variables which are used in the xbt_cleanup or xbt_catch clauses must be
212 * declared before the xbt_try clause, otherwise they only exist inside the
213 * xbt_try block. In the example above, cp1, cp2 and cp3 only exist in the
214 * xbt_try block and are invisible from the xbt_cleanup and xbt_catch
216 * -# \b variable initialization \n
217 * Variables which are used in the xbt_cleanup or xbt_catch clauses must
218 * be initialized before the point of the first possible xbt_throw is
219 * reached. In the example above, xbt_cleanup would have trouble using cp3
220 * if mallocex() throws a exception when allocating a TOOBIG buffer.
221 * -# \b volatile variable \n
222 * Variables which are used in the xbt_cleanup or xbt_catch clauses MUST BE
223 * DECLARED AS "volatile", otherwise they might contain outdated
224 * information when an exception is thrown.
225 * -# \b clean before catch \n
226 * The xbt_cleanup clause is not only place before the xbt_catch clause in
227 * the source code, it also occures before in the control flow. So,
228 * resources being cleaned up cannot be used in the xbt_catch block. In the
229 * example, c3 gets freed before the printf placed in xbt_catch.
230 * -# \b variable uninitialization \n
231 * If resources are passed out of the scope of the
232 * xbt_try/xbt_cleanup/xbt_catch construct, they naturally shouldn't get
233 * cleaned up. The example above does free(3) cp1 in xbt_cleanup although
234 * its value was affected to globalcontext->first, invalidating this
237 * The following is fixed version of the code (annotated with the pitfall items
242 char * volatile / *03* / cp1 = NULL / *02* /;
243 char * volatile / *03* / cp2 = NULL / *02* /;
244 char * volatile / *03* / cp3 = NULL / *02* /;
246 cp1 = mallocex(SMALLAMOUNT);
247 globalcontext->first = cp1;
248 cp1 = NULL / *05 give away* /;
249 cp2 = mallocex(TOOBIG);
250 cp3 = mallocex(SMALLAMOUNT);
255 printf("cp3=%s", cp3 == NULL / *02* / ? "" : cp3);
260 / *05 cp1 was given away * /
263 / *05 global context untouched * /
272 /** @brief Structure describing an exception */
274 char *msg; /**< human readable message; to be freed */
275 int category; /**< category like HTTP (what went wrong) */
276 int value; /**< like errno (why did it went wrong) */
278 char *host; /* NULL for localhost; hostname:port if remote */
280 char *file; /**< to be freed only for remote exceptions */
282 char *func; /**< to be freed only for remote exceptions */
285 /* declare the context type (private) */
287 __ex_mctx_t *ctx_mctx; /* permanent machine context of enclosing try/catch */
288 int ctx_deferred; /* permanent flag whether exception is deferred */
289 int ctx_deferring;/* permanent counter of exception deferring level */
290 int ctx_defer; /* temporary flag for exception deferring macro */
291 int ctx_shielding;/* permanent counter of exception shielding level */
292 int ctx_shield; /* temporary flag for exception shielding macro */
293 int ctx_caught; /* temporary flag whether exception was caught */
294 volatile ex_t ctx_ex; /* temporary exception storage */
297 /* the static and dynamic initializers for a context structure */
298 #define XBT_CTX_INITIALIZER \
299 { NULL, 0, 0, 0, 0, 0, 0, { /* content */ NULL, 0, 0, \
300 /*throw point*/ NULL, NULL, NULL, 0, NULL } }
301 #define XBT_CTX_INITIALIZE(ctx) \
303 (ctx)->ctx_mctx = NULL; \
304 (ctx)->ctx_deferred = 0; \
305 (ctx)->ctx_deferring = 0; \
306 (ctx)->ctx_defer = 0; \
307 (ctx)->ctx_shielding = 0; \
308 (ctx)->ctx_shield = 0; \
309 (ctx)->ctx_caught = 0; \
310 (ctx)->ctx_ex.msg = NULL; \
311 (ctx)->ctx_ex.category = 0; \
312 (ctx)->ctx_ex.value = 0; \
313 (ctx)->ctx_ex.host = NULL; \
314 (ctx)->ctx_ex.procname = NULL; \
315 (ctx)->ctx_ex.file = NULL; \
316 (ctx)->ctx_ex.line = 0; \
317 (ctx)->ctx_ex.func = NULL; \
320 /* the exception context */
321 typedef ex_ctx_t *(*ex_ctx_cb_t)(void);
322 extern ex_ctx_cb_t __xbt_ex_ctx;
323 extern ex_ctx_t *__xbt_ex_ctx_default(void);
325 /* the termination handler */
326 typedef void (*ex_term_cb_t)(ex_t *);
327 extern ex_term_cb_t __xbt_ex_terminate;
328 extern void __xbt_ex_terminate_default(ex_t *e);
330 /** @brief Introduce a block where exception may be dealed with
335 ex_ctx_t *__xbt_ex_ctx_ptr = __xbt_ex_ctx(); \
336 int __ex_cleanup = 0; \
337 __ex_mctx_t *__ex_mctx_en; \
338 __ex_mctx_t __ex_mctx_me; \
339 __ex_mctx_en = __xbt_ex_ctx_ptr->ctx_mctx; \
340 __xbt_ex_ctx_ptr->ctx_mctx = &__ex_mctx_me; \
341 if (__ex_mctx_save(&__ex_mctx_me)) { \
344 /** @brief optional(!) block for cleanup
347 #define xbt_cleanup \
350 __xbt_ex_ctx_ptr->ctx_caught = 0; \
353 __ex_mctx_restored(&__ex_mctx_me); \
354 __xbt_ex_ctx_ptr->ctx_caught = 1; \
356 __xbt_ex_ctx_ptr->ctx_mctx = __ex_mctx_en; \
361 /** @brief the block for catching (ie, deal with) an exception
364 #define xbt_catch(e) \
367 if (!(__ex_cleanup)) \
368 __xbt_ex_ctx_ptr->ctx_caught = 0; \
371 if (!(__ex_cleanup)) { \
372 __ex_mctx_restored(&__ex_mctx_me); \
373 __xbt_ex_ctx_ptr->ctx_caught = 1; \
376 __xbt_ex_ctx_ptr->ctx_mctx = __ex_mctx_en; \
378 if ( !(__xbt_ex_ctx()->ctx_caught) \
379 || ((e) = __xbt_ex_ctx()->ctx_ex, 0)) { \
383 /** @brief Build an exception from the supplied arguments and throws it
386 * If called from within a sg_try/sg_catch construct, this exception
387 * is copied into the sg_catch relevant variable program control flow
388 * is derouted to the sg_catch (after the optional sg_cleanup).
390 * If no sg_try/sg_catch conctruct embeeds this call, the program calls
393 * The sg_throw can be performed everywhere, including inside sg_try,
394 * sg_cleanup and sg_catch blocks.
396 #define xbt_throw(c,v,m) \
397 (( __xbt_ex_ctx()->ctx_shielding > 0 \
398 || (__xbt_ex_ctx()->ctx_deferring > 0 && __xbt_ex_ctx()->ctx_deferred == 1)) ? 0 : \
399 (__xbt_ex_ctx()->ctx_ex.msg = bprintf(m), \
400 __xbt_ex_ctx()->ctx_ex.category = (c), \
401 __xbt_ex_ctx()->ctx_ex.value = (v), \
402 __xbt_ex_ctx()->ctx_ex.host = (char*)NULL, \
403 __xbt_ex_ctx()->ctx_ex.procname = strdup(xbt_procname()), \
404 __xbt_ex_ctx()->ctx_ex.file = (char*)__FILE__, \
405 __xbt_ex_ctx()->ctx_ex.line = __LINE__, \
406 __xbt_ex_ctx()->ctx_ex.func = (char*)_XBT_FUNCTION, \
407 __xbt_ex_ctx()->ctx_deferred = 1, \
408 (__xbt_ex_ctx()->ctx_deferring > 0 ? 0 : \
409 (__xbt_ex_ctx()->ctx_mctx == NULL \
410 ? (__xbt_ex_terminate((ex_t *)&(__xbt_ex_ctx()->ctx_ex)), -1) \
411 : (__ex_mctx_restore(__xbt_ex_ctx()->ctx_mctx), 1) ))))
413 /** @brief re-throwing of an already caught exception (ie, pass it to the upper catch block)
416 #define xbt_rethrow \
417 (( __xbt_ex_ctx()->ctx_shielding > 0 \
418 || __xbt_ex_ctx()->ctx_deferring > 0) ? 0 : \
419 ( __xbt_ex_ctx()->ctx_mctx == NULL \
420 ? (__xbt_ex_terminate((ex_t *)&(__xbt_ex_ctx()->ctx_ex)), -1) \
421 : (__ex_mctx_restore(__xbt_ex_ctx()->ctx_mctx), 1) ))
423 /** @brief shield an operation from exception handling
427 for (__xbt_ex_ctx()->ctx_shielding++, \
428 __xbt_ex_ctx()->ctx_shield = 1; \
429 __xbt_ex_ctx()->ctx_shield == 1; \
430 __xbt_ex_ctx()->ctx_shield = 0, \
431 __xbt_ex_ctx()->ctx_shielding--)
433 /** @brief defer immediate exception handling
437 for (((__xbt_ex_ctx()->ctx_deferring)++ == 0 ? __xbt_ex_ctx()->ctx_deferred = 0 : 0), \
438 __xbt_ex_ctx()->ctx_defer = 1; \
439 __xbt_ex_ctx()->ctx_defer == 1; \
440 __xbt_ex_ctx()->ctx_defer = 0, \
441 ((--(__xbt_ex_ctx()->ctx_deferring) == 0 && __xbt_ex_ctx()->ctx_deferred == 1) ? xbt_rethrow : 0))
443 /** @brief exception handling tests
446 #define xbt_catching \
447 (__xbt_ex_ctx()->ctx_mctx != NULL)
448 /** @brief exception handling tests
451 #define xbt_shielding \
452 (__xbt_ex_ctx()->ctx_shielding > 0)
453 /** @brief exception handling tests
456 #define xbt_deferring \
457 (__xbt_ex_ctx()->ctx_deferring > 0)
459 /* optional namespace mapping */
460 #if defined(__EX_NS_UCCXX__)
462 #define Cleanup xbt_cleanup
463 #define Catch xbt_catch
464 #define Throw xbt_throw
465 #define Rethrow xbt_rethrow
466 #define Shield xbt_shield
467 #define Defer xbt_defer
468 #elif defined(__EX_NS_CXX__) || (!defined(__cplusplus) && !defined(__EX_NS_CUSTOM__))
470 #define cleanup xbt_cleanup
471 #define catch xbt_catch
472 #define throw xbt_throw
473 #define rethrow xbt_rethrow
474 #define shield xbt_shield
475 #define defer xbt_defer
479 #endif /* __XBT_EX_H__ */