From: kagel AT quasar DOT bloomberg DOT com Date: Wed, 10 Jan 1996 17:44:13 -0500 To: dunder AT nyongwa DOT montreal DOT qc DOT ca Cc: djgpp AT delorie DOT com Subject: Re: (none) Reply-To: kagel AT quasar DOT bloomberg DOT com Date: Wed, 10 Jan 1996 14:53:28 -0500 (EST) From: dunder > >Segment violation in pointer 0x00000000 at d8:de81 > > > >It works fine compiled with TC... Is this error sent by a particular bug > >en DJGPP or by some 'TC supported' functions or syntax that GCC handles > >badly? Thanx > > You're looking for a bug in the wrong place. The bug isn't in djgpp, > the bug is in your program. At some point in your program you are > dereferencing a NULL pointer. Turbo C didn't catch the bug because > there is no memory protection in real mode. Turbo C will let you smash > the interrupt table with reckless abandon. > > The easiest way to find the bug is to use the debugger. It should be > able to tell you where the error happened. > > Eric Well actually I doubt i'd trash the interrupt table since we don't assing anything to it at the beginning, therefor, I guess, it points to *nowhere* or *anywhere*. The problem we found (after hours of debugging!) is that TC handles NULL pointers by returning a NULL value when comparing pointers (ie if(my_pointer) my_pointer[x] = z;) that is, if my pointer is initialised, give it a value. Else initialize it. Anyway we remade all the program remodeling the pointer uses and now it works fine with TC and GCC! (actually much better in GCC ;) ) Thanx all! Hmm btw, how can we test if a pointer is NULL?! Just as you did, ie: if (!my_pointer) my_pointer = (my_struct_t *)malloc( sizeof (my_struct_t) ); Or BETTER CODE but equivalent: if (my_pointer == (my_struct_t *)NULL) ... -- Art S. Kagel, kagel AT quasar DOT bloomberg DOT com A proverb is no proverb to you 'till life has illustrated it. -- John Keats