[simgrid.git] / include / xbt / ex.h

/* $Id$ */

/* ex - Exception Handling (modified to fit into SimGrid from OSSP version) */

/*  Copyright (c) 2005-2006 Martin Quinson                                  */
/*  Copyright (c) 2002-2004 Ralf S. Engelschall <rse@engelschall.com>       */
/*  Copyright (c) 2002-2004 The OSSP Project <http://www.ossp.org/>         */
/*  Copyright (c) 2002-2004 Cable & Wireless <http://www.cw.com/>           */
/*  All rights reserved.                                                    */

/* This program is free software; you can redistribute it and/or modify it
  * under the terms of the license (GNU LGPL) which comes with this package. */

#ifndef __XBT_EX_H__
#define __XBT_EX_H__

#include <xbt/sysdep.h>
#include <xbt/misc.h>

/* do not include execinfo.h directly since it's not always available. 
   Instead, copy the parts we need (and fake when it's not there) */
extern int backtrace (void **__array, int __size);

/* required ISO-C standard facilities */
#include <errno.h>
#include <stdio.h>


/*-*-* Emergency debuging: define this when the exceptions get crazy *-*-*/
#undef __EX_MAYDAY

#ifdef __EX_MAYDAY
int gras_os_getpid(void);
#  define MAYDAY_SAVE(m)    printf("%d %s:%d save %p\n",                \
                                   gras_os_getpid(),__FILE__,__LINE__,  \
                                   (m)->jb                              \
                                  ),
#  define MAYDAY_RESTORE(m) printf("%d %s:%d restore %p\n",             \
                                   gras_os_getpid(),__FILE__,__LINE__,  \
                                   (m)->jb                              \
                                  ),
#  define MAYDAY_CATCH(e)   printf("%d %s:%d Catched '%s'\n",           \
                                   gras_os_getpid(),__FILE__,__LINE__,  \
                                   e.msg                                \
                                  ),
#else
#  define MAYDAY_SAVE(m)
#  define MAYDAY_RESTORE(m)
#  define MAYDAY_CATCH(e)
#endif

/*-*-* end of debugging stuff *-*-*/


/* the machine context */
#if defined(__EX_MCTX_MCSC__)
#include <ucontext.h>            /* POSIX.1 ucontext(3) */
#define __ex_mctx_struct         ucontext_t uc;
#define __ex_mctx_save(mctx)     (getcontext(&(mctx)->uc) == 0)
#define __ex_mctx_restored(mctx) /* noop */
#define __ex_mctx_restore(mctx)  (void)setcontext(&(mctx)->uc)

#elif defined(__EX_MCTX_SSJLJ__)
#include <setjmp.h>              /* POSIX.1 sigjmp_buf(3) */
#define __ex_mctx_struct         sigjmp_buf jb;
#define __ex_mctx_save(mctx)     (sigsetjmp((mctx)->jb, 1) == 0)
#define __ex_mctx_restored(mctx) /* noop */
#define __ex_mctx_restore(mctx)  (void)siglongjmp((mctx)->jb, 1)

#elif defined(__EX_MCTX_SJLJ__) || !defined(__EX_MCTX_CUSTOM__) || defined(__EX_MAYDAY)
#include <setjmp.h>              /* ISO-C jmp_buf(3) */
#define __ex_mctx_struct         jmp_buf jb;
#define __ex_mctx_save(mctx)     ( MAYDAY_SAVE(mctx) setjmp((mctx)->jb) == 0)
#define __ex_mctx_restored(mctx) /* noop */
#define __ex_mctx_restore(mctx)  ( MAYDAY_RESTORE(mctx) (void)longjmp((mctx)->jb, 1))
#endif

/* declare the machine context type */
typedef struct { __ex_mctx_struct } __ex_mctx_t;

/** @addtogroup XBT_ex
 *  @brief A set of macros providing exception a la C++ in ANSI C (grounding feature)
 *
 * This module is a small ISO-C++ style exception handling library
 * for use in the ISO-C language. It allows you to use the paradigm 
 * of throwing and catching exceptions in order to reduce the amount
 * of error handling code without hindering program robustness.
 *               
 * This is achieved by directly transferring exceptional return codes
 * (and the program control flow) from the location where the exception
 * is raised (throw point) to the location where it is handled (catch
 * point) -- usually from a deeply nested sub-routine to a parent 
 * routine. All intermediate routines no longer have to make sure that 
 * the exceptional return codes from sub-routines are correctly passed 
 * back to the parent.
 *
 * These features are brought to you by a modified version of the libex 
 * library, one of the numerous masterpiece of Ralf S. Engelschall.
 *
 * \htmlonly <div class="toc">\endhtmlonly
 *
 * @section XBT_ex_toc TABLE OF CONTENTS
 *
 *  - \ref XBT_ex_intro
 *  - \ref XBT_ex_base
 *  - \ref XBT_ex_pitfalls
 *
 * \htmlonly </div> \endhtmlonly
 *
 * @section XBT_ex_intro DESCRIPTION
 * 
 * In SimGrid, an exception is a triple <\a msg , \a category , \a value> 
 * where \a msg is a human-readable text describing the exceptional 
 * condition, \a code an integer describing what went wrong and \a value
 * providing a sort of sub-category. (this is different in the original libex).
 *
 * @section XBT_ex_base BASIC USAGE
 *
 * \em TRY \b TRIED_BLOCK [\em CLEANUP \b CLEANUP_BLOCK] \em CATCH (variable) \b CATCH_BLOCK
 *
 * This is the primary syntactical construct provided. It is modeled after the
 * ISO-C++ try-catch clause and should sound familiar to most of you.
 *
 * Any exception thrown directly from the TRIED_BLOCK block or from called
 * subroutines is caught. Cleanups which must be done after this block
 * (whenever an exception arised or not) should be placed into the optionnal
 * CLEANUP_BLOCK. The code dealing with the exceptions when they arise should
 * be placed into the (mandatory) CATCH_BLOCK.
 *
 * 
 * In absence of exception, the control flow goes into the blocks TRIED_BLOCK
 * and CLEANUP_BLOCK (if present); The CATCH_BLOCK block is then ignored. 
 *
 * When an exception is thrown, the control flow goes through the following
 * blocks: TRIED_BLOCK (up to the statement throwing the exception),
 * CLEANUP_BLOCK (if any) and CATCH_BLOCK. The exception is stored in a
 * variable for inspection inside the CATCH_BLOCK. This variable must be
 * declared in the outter scope, but its value is only valid within the
 * CATCH_BLOCK block. 
 *
 * Some notes:
 *  - TRY, CLEANUP and CATCH cannot be used separately, they work
 *    only in combination and form a language clause as a whole.
 *  - In contrast to the syntax of other languages (such as C++ or Jave) there
 *    is only one CATCH block and not multiple ones (all exceptions are
 *    of the same \em xbt_ex_t C type). 
 *  - the variable of CATCH can naturally be reused in subsequent 
 *    CATCH clauses.
 *  - it is possible to nest TRY clauses.
 *
 * The TRY block is a regular ISO-C language statement block, but
 * 
 * <center><b>it is not
 * allowed to jump into it via "goto" or longjmp(3) or out of it via "break",
 * "return", "goto" or longjmp(3)</b>.</center>
 *
 * This is because there is some hidden setup and
 * cleanup that needs to be done regardless of whether an exception is
 * caught. Bypassing these steps will break the exception handling facility.
 *     
 * The CLEANUP and CATCH blocks are regular ISO-C language statement
 * blocks without any restrictions. You are even allowed to throw (and, in the
 * CATCH block, to re-throw) exceptions.
 *
 * There is one subtle detail you should remember about TRY blocks:
 * Variables used in the CLEANUP or CATCH clauses must be declared with
 * the storage class "volatile", otherwise they might contain outdated
 * information if an exception it thrown.
 *
 *
 * This is because you usually do not know which commands in the TRY
 * were already successful before the exception was thrown (logically speaking)
 * and because the underlying ISO-C setjmp(3) facility applies those
 * restrictions (technically speaking). As a matter of fact, value changes
 * between the TRY and the THROW may be discarded if you forget the
 * "volatile" keyword. 
 * 
 * \section XBT_ex_pitfalls PROGRAMMING PITFALLS 
 *
 * Exception handling is a very elegant and efficient way of dealing with
 * exceptional situation. Nevertheless it requires additional discipline in
 * programming and there are a few pitfalls one must be aware of. Look the
 * following code which shows some pitfalls and contains many errors (assuming
 * a mallocex() function which throws an exception if malloc(3) fails):
 *
 * \dontinclude ex.c
 * \skip BAD_EXAMPLE
 * \until end_of_bad_example
 *
 * This example raises a few issues:
 *  -# \b variable \b scope \n
 *     Variables which are used in the CLEANUP or CATCH clauses must be
 *     declared before the TRY clause, otherwise they only exist inside the
 *     TRY block. In the example above, cp1, cp2 and cp3 only exist in the
 *     TRY block and are invisible from the CLEANUP and CATCH
 *     blocks.
 *  -# \b variable \b initialization \n
 *     Variables which are used in the CLEANUP or CATCH clauses must
 *     be initialized before the point of the first possible THROW is
 *     reached. In the example above, CLEANUP would have trouble using cp3
 *     if mallocex() throws a exception when allocating a TOOBIG buffer.
 *  -# \b volatile \b variable \n
 *     Variables which are used in the CLEANUP or CATCH clauses MUST BE
 *     DECLARED AS "volatile", otherwise they might contain outdated
 *     information when an exception is thrown. 
 *  -# \b clean \b before \b catch \n
 *     The CLEANUP clause is not only place before the CATCH clause in
 *     the source code, it also occures before in the control flow. So,
 *     resources being cleaned up cannot be used in the CATCH block. In the
 *     example, c3 gets freed before the printf placed in CATCH.
 *  -# \b variable \b uninitialization \n
 *     If resources are passed out of the scope of the
 *     TRY/CLEANUP/CATCH construct, they naturally shouldn't get
 *     cleaned up. The example above does free(3) cp1 in CLEANUP although
 *     its value was affected to globalcontext->first, invalidating this
 *     pointer.

 * The following is fixed version of the code (annotated with the pitfall items
 * for reference): 
 *
 * \skip GOOD_EXAMPLE
 * \until end_of_good_example
 *
 * @{
 */

/* we need this symbol here, even if it breaks a bit the module separation */
long int gras_os_getpid(void);

/** @brief different kind of errors */
typedef enum {
  unknown_error=0,  /**< unknown error */
  arg_error,        /**< Invalid argument */
  mismatch_error,   /**< The provided ID does not match */
  not_found_error,  /**< The searched element was not found */
  
  system_error,   /**< a syscall did fail */
  network_error,  /**< error while sending/receiving data */
  timeout_error,  /**< not quick enough, dude */
  thread_error    /**< error while [un]locking */
} xbt_errcat_t;

const char * xbt_ex_catname(xbt_errcat_t cat);

/** @brief Structure describing an exception */
typedef struct {
  char        *msg;      /**< human readable message; to be freed */
  xbt_errcat_t category; /**< category like HTTP (what went wrong) */
  int          value;    /**< like errno (why did it went wrong) */
  /* throw point */
  short int remote; /* whether it was raised remotely */
  char *host;     /* NULL for localhost; hostname if remote */
  /* FIXME: host should be hostname:port[#thread] */
  char *procname; 
  long int pid;
  char *file;     /**< to be freed only for remote exceptions */
  int   line;     
  char *func;     /**< to be freed only for remote exceptions */
  /* Backtrace */
  int   used;
  char **bt_strings; /* only filed on display (or before the network propagation) */
  void *bt[XBT_BACKTRACE_SIZE];
} xbt_ex_t;

/* declare the context type (private) */
typedef struct {
    __ex_mctx_t  *ctx_mctx;     /* permanent machine context of enclosing try/catch */
    volatile int ctx_caught;    /* temporary flag whether exception was caught */
    volatile xbt_ex_t ctx_ex;   /* temporary exception storage */
} ex_ctx_t;

/* the static and dynamic initializers for a context structure */
#define XBT_CTX_INITIALIZER \
    { NULL, 0, { /* content */ NULL, unknown_error, 0, \
                 /* throw point*/ 0,NULL, NULL,0, NULL, 0, NULL,\
                 /* backtrace */ 0,NULL,{NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL} } }
#define XBT_CTX_INITIALIZE(ctx) \
    do { \
        (ctx)->ctx_mctx          = NULL; \
        (ctx)->ctx_caught        = 0;    \
        (ctx)->ctx_ex.msg        = NULL; \
        (ctx)->ctx_ex.category   = 0;    \
        (ctx)->ctx_ex.value      = 0;    \
        (ctx)->ctx_ex.remote     = 0;    \
        (ctx)->ctx_ex.host       = NULL; \
        (ctx)->ctx_ex.procname   = NULL; \
        (ctx)->ctx_ex.pid        = 0;    \
        (ctx)->ctx_ex.file       = NULL; \
        (ctx)->ctx_ex.line       = 0;    \
        (ctx)->ctx_ex.func       = NULL; \
        (ctx)->ctx_ex.bt[0]      = NULL; \
        (ctx)->ctx_ex.bt[1]      = NULL; \
        (ctx)->ctx_ex.bt[2]      = NULL; \
        (ctx)->ctx_ex.bt[3]      = NULL; \
        (ctx)->ctx_ex.bt[4]      = NULL; \
        (ctx)->ctx_ex.bt[5]      = NULL; \
        (ctx)->ctx_ex.bt[6]      = NULL; \
        (ctx)->ctx_ex.bt[7]      = NULL; \
        (ctx)->ctx_ex.bt[8]      = NULL; \
        (ctx)->ctx_ex.bt[9]      = NULL; \
        (ctx)->ctx_ex.used       = 0; \
        (ctx)->ctx_ex.bt_strings = NULL; \
    } while (0)

/* the exception context */
typedef ex_ctx_t *(*ex_ctx_cb_t)(void);
extern ex_ctx_cb_t __xbt_ex_ctx;
extern ex_ctx_t *__xbt_ex_ctx_default(void);

/* the termination handler */
typedef void (*ex_term_cb_t)(xbt_ex_t *);
extern ex_term_cb_t __xbt_ex_terminate;
extern void __xbt_ex_terminate_default(xbt_ex_t *e);

/** @brief Introduce a block where exception may be dealed with 
 *  @hideinitializer
 */
#define TRY \
    { \
        ex_ctx_t *__xbt_ex_ctx_ptr = __xbt_ex_ctx(); \
        int __ex_cleanup = 0; \
        __ex_mctx_t *__ex_mctx_en; \
        __ex_mctx_t __ex_mctx_me; \
        __ex_mctx_en = __xbt_ex_ctx_ptr->ctx_mctx; \
        __xbt_ex_ctx_ptr->ctx_mctx = &__ex_mctx_me; \
        if (__ex_mctx_save(&__ex_mctx_me)) { \
            if (1)

/** @brief optional(!) block for cleanup 
 *  @hideinitializer
 */
#define CLEANUP \
            else { \
            } \
            __xbt_ex_ctx_ptr->ctx_caught = 0; \
        } else { \
            __ex_mctx_restored(&__ex_mctx_me); \
            __xbt_ex_ctx_ptr->ctx_caught = 1; \
        } \
        __xbt_ex_ctx_ptr->ctx_mctx = __ex_mctx_en; \
        __ex_cleanup = 1; \
        if (1) { \
            if (1)

#ifndef DOXYGEN_SKIP
#  ifdef __cplusplus
#    define XBT_EX_T_CPLUSPLUSCAST (xbt_ex_t&)
#  else
#    define XBT_EX_T_CPLUSPLUSCAST 
#  endif
#endif

/** @brief the block for catching (ie, deal with) an exception 
 *  @hideinitializer
 */
#define CATCH(e) \
            else { \
            } \
            if (!(__ex_cleanup)) \
                __xbt_ex_ctx_ptr->ctx_caught = 0; \
        } else { \
            if (!(__ex_cleanup)) { \
                __ex_mctx_restored(&__ex_mctx_me); \
                __xbt_ex_ctx_ptr->ctx_caught = 1; \
            } \
        } \
        __xbt_ex_ctx_ptr->ctx_mctx = __ex_mctx_en; \
    } \
    if (   !(__xbt_ex_ctx()->ctx_caught) \
        || ((e) = XBT_EX_T_CPLUSPLUSCAST __xbt_ex_ctx()->ctx_ex, MAYDAY_CATCH(e) 0)) { \
    } \
    else

#define DO_THROW(e) \
     /* deal with the exception */                                             \
     if (__xbt_ex_ctx()->ctx_mctx == NULL)                                     \
       __xbt_ex_terminate((xbt_ex_t *)&(e)); /* not catched */\
     else                                                                      \
       __ex_mctx_restore(__xbt_ex_ctx()->ctx_mctx); /* catched somewhere */    \
     abort()/* nope, stupid GCC, we won't survive a THROW (this won't be reached) */

/** @brief Helper macro for THROWS0-6
 *  @hideinitializer
 *
 *  @param c: category code (integer)
 *  @param v: value (integer)
 *  @param m: message text
 *
 * If called from within a TRY/CATCH construct, this exception 
 * is copied into the CATCH relevant variable program control flow 
 * is derouted to the CATCH (after the optional sg_cleanup). 
 *
 * If no TRY/CATCH construct embeeds this call, the program calls
 * abort(3). 
 *
 * The THROW can be performed everywhere, including inside TRY, 
 * CLEANUP and CATCH blocks.
 */

#define _THROW(c,v,m) \
  do { /* change this sequence into one block */                              \
     /* build the exception */                                                \
     __xbt_ex_ctx()->ctx_ex.msg      = (m);                                   \
     __xbt_ex_ctx()->ctx_ex.category = (xbt_errcat_t)(c);                     \
     __xbt_ex_ctx()->ctx_ex.value    = (v);                                   \
     __xbt_ex_ctx()->ctx_ex.remote   = 0;                                     \
     __xbt_ex_ctx()->ctx_ex.host     = (char*)NULL;                           \
     __xbt_ex_ctx()->ctx_ex.procname = (char*)xbt_procname();                 \
     __xbt_ex_ctx()->ctx_ex.pid      = gras_os_getpid();                      \
     __xbt_ex_ctx()->ctx_ex.file     = (char*)__FILE__;                       \
     __xbt_ex_ctx()->ctx_ex.line     = __LINE__;                              \
     __xbt_ex_ctx()->ctx_ex.func     = (char*)_XBT_FUNCTION;                  \
     __xbt_ex_ctx()->ctx_ex.used     = backtrace((void**)__xbt_ex_ctx()->ctx_ex.bt,XBT_BACKTRACE_SIZE);\
     __xbt_ex_ctx()->ctx_ex.bt_strings = NULL; \
     DO_THROW(__xbt_ex_ctx()->ctx_ex);\
  } while (0)

/** @brief Builds and throws an exception with a string taking no arguments
    @hideinitializer */
#define THROW0(c,v,m)                   _THROW(c,v,(m?bprintf(m):NULL))
/** @brief Builds and throws an exception with a string taking one argument
    @hideinitializer */
#define THROW1(c,v,m,a1)                _THROW(c,v,bprintf(m,a1))
/** @brief Builds and throws an exception with a string taking two arguments
    @hideinitializer */
#define THROW2(c,v,m,a1,a2)             _THROW(c,v,bprintf(m,a1,a2))
/** @brief Builds and throws an exception with a string taking three arguments
    @hideinitializer */
#define THROW3(c,v,m,a1,a2,a3)          _THROW(c,v,bprintf(m,a1,a2,a3))
/** @brief Builds and throws an exception with a string taking four arguments
    @hideinitializer */
#define THROW4(c,v,m,a1,a2,a3,a4)       _THROW(c,v,bprintf(m,a1,a2,a3,a4))
/** @brief Builds and throws an exception with a string taking five arguments
    @hideinitializer */
#define THROW5(c,v,m,a1,a2,a3,a4,a5)    _THROW(c,v,bprintf(m,a1,a2,a3,a4,a5))
/** @brief Builds and throws an exception with a string taking six arguments
    @hideinitializer */
#define THROW6(c,v,m,a1,a2,a3,a4,a5,a6) _THROW(c,v,bprintf(m,a1,a2,a3,a4,a5,a6))

#define THROW_IMPOSSIBLE     THROW0(unknown_error,0,"The Impossible Did Happen (yet again)")
#define THROW_UNIMPLEMENTED  THROW1(unknown_error,0,"Function %s unimplemented",__FUNCTION__)

#ifndef NDEBUG
#  define DIE_IMPOSSIBLE       xbt_assert0(0,"The Impossible Did Happen (yet again)")
#else
#  define DIE_IMPOSSIBLE       exit(1);
#endif

/** @brief re-throwing of an already caught exception (ie, pass it to the upper catch block) 
 *  @hideinitializer
 */
#define RETHROW \
  do { \
   if (__xbt_ex_ctx()->ctx_mctx == NULL) \
     __xbt_ex_terminate((xbt_ex_t *)&(__xbt_ex_ctx()->ctx_ex)); \
   else \
     __ex_mctx_restore(__xbt_ex_ctx()->ctx_mctx); \
   abort();\
  } while(0)


#ifndef DOXYGEN_SKIP
#define _XBT_PRE_RETHROW \
  do {                                                               \
    char *_xbt_ex_internal_msg = __xbt_ex_ctx()->ctx_ex.msg;         \
    __xbt_ex_ctx()->ctx_ex.msg = bprintf(
#define _XBT_POST_RETHROW \
 _xbt_ex_internal_msg); \
    free(_xbt_ex_internal_msg);                                      \
    RETHROW;                                                         \
  } while (0)
#endif

/** @brief like THROW0, but adding some details to the message of an existing exception
 *  @hideinitializer
 */
#define RETHROW0(msg)           _XBT_PRE_RETHROW msg,          _XBT_POST_RETHROW
/** @brief like THROW1, but adding some details to the message of an existing exception
 *  @hideinitializer
 */
#define RETHROW1(msg,a)         _XBT_PRE_RETHROW msg,a,        _XBT_POST_RETHROW
/** @brief like THROW2, but adding some details to the message of an existing exception
 *  @hideinitializer
 */
#define RETHROW2(msg,a,b)       _XBT_PRE_RETHROW msg,a,b,      _XBT_POST_RETHROW
/** @brief like THROW3, but adding some details to the message of an existing exception
 *  @hideinitializer
 */
#define RETHROW3(msg,a,b,c)     _XBT_PRE_RETHROW msg,a,b,c,    _XBT_POST_RETHROW
/** @brief like THROW4, but adding some details to the message of an existing exception
 *  @hideinitializer
 */
#define RETHROW4(msg,a,b,c,d)   _XBT_PRE_RETHROW msg,a,b,c,    _XBT_POST_RETHROW
/** @brief like THROW5, but adding some details to the message of an existing exception
 *  @hideinitializer
 */
#define RETHROW5(msg,a,b,c,d,e) _XBT_PRE_RETHROW msg,a,b,c,d,e _XBT_POST_RETHROW

/** @brief Exception destructor */
void xbt_ex_free(xbt_ex_t e);

void xbt_ex_display(xbt_ex_t *e);
void xbt_backtrace_display(void);

/** @} */
#endif /* __XBT_EX_H__ */