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From: comeau@ditka.Chicago.COM (Greg Comeau)
Newsgroups: comp.sys.amiga.programmer
Subject: Re: Debugging C++
Message-ID: <38579@ditka.Chicago.COM>
Date: 10 May 91 14:30:19 GMT
References: <1991May5.222328.16225@csis.dit.csiro.au> <616@lysator.liu.se> <38542@ditka.Chicago.COM>
Sender: comeau@ditka.Chicago.COM (Greg Comeau)
Reply-To: comeau@csanta.attmail.com (Greg Comeau)
Organization: Comeau Computing
Lines: 80

Previous "debugging C++" thread have been expired from this machine
(which is unfortunate since I wanted to address some specific points
some of you made/asked about).  Nevertheless, it's created enough
interest that I've felt y'all need an answer.

So.  Given:
#include <stdio.h>
int a = -3;
main()
{ 
    printf("hello, world\n");
    printf("a=%d\n", a);
}

we generate output like:

#line 1 "c.c"
/* <<Comeau C++ Translator 2.1.0 05/16/90>> */
/* < c.c > */
#line 1 "c.c"
char *__vec_new ();
#line 1 "c.c"
char __vec_delete ();
typedef int (*__vptp)();
struct __mptr {short d; short i; __vptp f; };
#line 1 "c.c"
#line 6 "work:aztec/include/stdarg.h"
typedef char *va_list ;
#line 10 "work:aztec/include/stdio.h"
typedef unsigned long size_t ;
#line 34 "work:aztec/include/stdio.h"
typedef long fpos_t ;
#line 45 "work:aztec/include/stdio.h"
typedef struct __stdio FILE ;
#line 36 "work:aztec/include/stdio.h"
struct __stdio {	/* sizeof __stdio == 24 */
unsigned char *_bp__7__stdio ;
unsigned char *_bend__7__stdio ;
unsigned char *_buff__7__stdio ;
unsigned short _flags__7__stdio ;
char _unit__7__stdio ;
unsigned char _bytbuf__7__stdio ;
size_t _buflen__7__stdio ;
unsigned short _tmpnum__7__stdio ;
};
extern struct __stdio _iob [];
#line 3 "c.c"
int a = -3;
extern struct __mptr* __ptbl_vec__c_c_a_[];
#line 76 "work:aztec/include/stdio.h"
extern int printf ();
#line 5 "c.c"
int main (){ _ConStrucT(); 
#line 6 "c.c"
{ 
#line 7 "c.c"
printf ( (char *)"hello, world\n") ;
printf ( (char *)"a=%d\n", a ) ;
}
} 
#line 9 "c.c"
/* the end */

With the prodding that's been visible here, I went and did a quicky
compile of c.c with como (our command line driver) both with a SAS C
back-end and with as still in-house not released Manx C back-end (surprise!)
with debugging turned on.  In the Manx sdb case, it worked like a champ.
In the SAS CPR case it displayed the proper file but appears the the
debugging information contained line number relative to the top of
the generated C file and did not pick up the #line line numbers.
Most likely I did not use the right SAS C debugging switch as I've
yet to see this technique fail yet (and I'm convinced that I did this
before we released the SAS back end one).

- Greg
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