coredump

coredump

[Puneet Singhal]

Hi all

I compiled a program on linked lists using gcc


Here is a snapshot of the code...

1.          pBind->pNext = (PLLBIND)( (char *)pBind + usTrueAtomSize );
2.          (pBind->pNext)->pPrev = pBind;
3.          pBind = pBind->pNext;

statement no 2 is giving core.

pBind or pNext is Not NULL.

can anyone tell me why??

Also are there any good containers written in C available on the net.

TIA,
Puneet


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Re: coredump

[Soubhik Bhattacharya]

:
:Here is a snapshot of the code...
:
:1.          pBind->pNext = (PLLBIND)( (char *)pBind + usTrueAtomSize );
:2.          (pBind->pNext)->pPrev = pBind;
:3.          pBind = pBind->pNext;
:
:statement no 2 is giving core.
:
:pBind or pNext is Not NULL.
:

alignment problem?? are you sure that (pBind->pNext) is properly aligned
for PLLBIND, after execution of stmt 1 ?

--soubhik.

Re: Coredump

[Alexandre Oliva]

On Dec 14, 2000, "Puneet Singhal" <puneet@opussoft.com> wrote:

> The same code works fine on NCR UNIX

It works fine on all systems.  It's just a matter of defining `fine'.
The code invokes undefined behavior, so the run-time library is
entitled to do anything at all.  It might have formatted your hard
disk as well :-)

> When we port the same code to Solaris Sparc it gives a core dump why??

Because printf() ends up dereferencing the NULL pointer you passed to
it.  It might have checked whether the given pointer was NULL, but
then every single printf() of a string would incur this cost.  Why
impose this cost upon everybody, given that NULL isn't a valid string
anyway?

Besides, by having the program crash at that point, you can easily
figure out where the problem is from the stack trace you can get from
the core file, and fix it.  If printf just printed some odd string,
you'd have far more trouble figuring out which statement in your
program makes the invalid printf call.

-- 
Alexandre Oliva   Enjoy Guarana', see http://www.ic.unicamp.br/~oliva/
Red Hat GCC Developer                  aoliva@{cygnus.com, redhat.com}
CS PhD student at IC-Unicamp        oliva@{lsd.ic.unicamp.br, gnu.org}
Free Software Evangelist    *Please* write to mailing lists, not to me

RE: Coredump

[Puneet Singhal]

The same code works fine on NCR UNIX
When we port the same code to Solaris Sparc it gives a core dump why??


-----Original Message-----
From: gcc-help-owner@gcc.gnu.org [ mailto:gcc-help-owner@gcc.gnu.org]On
Behalf Of Alexandre Oliva
Sent: Wednesday, December 13, 2000 12:40 PM
To: Puneet Singhal
Cc: Gcchelp
Subject: Re: Coredump


On Dec 13, 2000, "Puneet Singhal" <puneet@opussoft.com> wrote:

> 	char *p=NULL;
> 	printf("%s", p);

> I get a coredump at runtime.

What did you expect?  You tell it to print a NUL-terminated string,
and don't give it a string at all.

-- 
Alexandre Oliva   Enjoy Guarana', see http://www.ic.unicamp.br/~oliva/
Red Hat GCC Developer                  aoliva@{cygnus.com, redhat.com}
CS PhD student at IC-Unicamp        oliva@{lsd.ic.unicamp.br, gnu.org}
Free Software Evangelist    *Please* write to mailing lists, not to me

Re: Coredump

[Alexandre Oliva]

On Dec 13, 2000, "Puneet Singhal" <puneet@opussoft.com> wrote:

> 	char *p=NULL;
> 	printf("%s", p);

> I get a coredump at runtime.

What did you expect?  You tell it to print a NUL-terminated string,
and don't give it a string at all.

-- 
Alexandre Oliva   Enjoy Guarana', see http://www.ic.unicamp.br/~oliva/
Red Hat GCC Developer                  aoliva@{cygnus.com, redhat.com}
CS PhD student at IC-Unicamp        oliva@{lsd.ic.unicamp.br, gnu.org}
Free Software Evangelist    *Please* write to mailing lists, not to me

Coredump

[Puneet Singhal]

Hi
I am compiling and linking the foll code with gcc-2.95.2 on Solaris 7 on
sparc.

int main()
{
	char *p=NULL;
	printf("%s", p);
	return 0;
}

I get a coredump at runtime. Please help..

I tried using the flag -fno-delete-null-pointer-checks for optimization but
gcc does not recognize this flag and gives an error.

Please Help!!

thanx
Puneet