error/exc.h

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/* Author: Andrew Schein   -*- c++ -*- */
/* C-based Exception library builds upon the MSG macros. */
/* Features:
 * 1. Finally-style functionality built in.
 * 2. Ability to throw with a message
 * 3. Backtrace on uncaught exceptions (turn on with compiler time flags)
*/

/* Tips for using C exceptions:
 *  1. Variables changed within a try statement must be volatile to prevent
 *  potential for sneaky errors
 *  2. Returns within TRY statement should use RETURN macro; RETURN pops the
 *  exception stack.
 *  3. Do not use your own longjmp within a CATCH context; the exception stack
 *   may become corrupt, and/or a memory leak may result.
 */

#ifndef NPS_EXC_H
#define NPS_EXC_H
#include <setjmp.h>
#include "../msg.h"

typedef struct Nps_exc_t {
  char *name;
} Nps_exc_t;

struct Nps_exc_frame_t {
  struct Nps_exc_frame_t *prev;
  jmp_buf target;
  const char *file;
  long line;
  char *msg;
  const Nps_exc_t *exc;
};

typedef struct Nps_exc_frame_t Nps_exc_frame_t;

enum { Nps_exc_entered=0, Nps_exc_thrown, Nps_exc_handled};

extern Nps_exc_frame_t *Nps_exc_stack; /* thread-local exception stack */

void nps_throw(const Nps_exc_t *e,const char *file, long line,const char*,...);

#define THROW(e,...) nps_throw(&(e),__FILE__,__LINE__,"" __VA_ARGS__)
#define RETHROW      nps_throw(_exc_top.exc,_exc_top.file,  \
                               _exc_top.line, _exc_top.msg)

#define TRY do {                                                        \
  volatile int Nps_exc_flag;                                            \
  Nps_exc_frame_t  _exc_top;                                            \
  _exc_top.msg   = NULL; /* non-null is a signal */                     \
  _exc_top.prev  = Nps_exc_stack;                                       \
  Nps_exc_stack    = &_exc_top;                                         \
  Nps_exc_flag     = setjmp(Nps_exc_stack->target);                     \
  if (Nps_exc_flag == Nps_exc_entered) {

#define CATCH                                                           \
  } /* Exiting TRY block */                                             \
    if (Nps_exc_stack != &_exc_top) {                                   \
      fprintf(stderr,"Exception stack is corrupted!\n");  exit(1);      \
    }                                                                   \
    Nps_exc_stack=Nps_exc_stack->prev;                                  \
    for (long nps_exc_catch_block=0; !nps_exc_catch_block && (Nps_exc_flag == Nps_exc_thrown); \
         nps_exc_catch_block=(Nps_exc_flag == Nps_exc_thrown ? RETHROW , 1 : \
                              free(_exc_top.msg),_exc_top.msg=NULL,1 ))   


#define ON(e)                                                           \
  for (long _nps_exc_on_block=0; (!_nps_exc_on_block && &(e) == _exc_top.exc); \
       ++_nps_exc_on_block,Nps_exc_flag=Nps_exc_handled)                \
    
#define END_TRY                                                         \
  if (_exc_top.msg) fprintf(stderr,"Corrupted exception stack\n"),exit(1); \
  } while (0); /* TRY do { */

#define RETURN switch (Nps_exc_stack = Nps_exc_stack->prev,0) default: return 

#endif

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