validate pointer that was returned from malloc

[Bryan Bullard]

Hi,

Is there a standard way to validate if a pointer points to memory that was
allocated by malloc?
TIA

[Andrey Tarasevich]

Bryan Bullard wrote:

Is there a standard way to validate if a pointer points to memory that was
allocated by malloc?

No.

--
Best regards,
Andrey Tarasevich

[Kristofer Pettijohn]

> Is there a standard way to validate if a pointer points to memory that was

allocated by malloc?

You would have to write your own wrapper for malloc for that one - that
might be fun. :)

Kristofer

[E. Robert Tisdale]

Bryan Bullard wrote:

Is there a standard way
No.
to validate if a pointer points to memory that was allocated by malloc? cat onStack.c

#include <stdio.h>
#include <stdlib.h>

int onStack(void* p) {
return (p > (void*)&p);
}

int main(int argc, char* argv[]) {
char c;
char* p = &c;
//char* p = (char*)malloc(s izeof(char));
if (onStack(p)) {
fprintf(stdout,
"p probably points to a character in automatic storage.\n");
}
else {
fprintf(stdout,
"p probably points to static data or free storage.\n");
}
return 0;
}

[Bryan Bullard]

"E. Robert Tisdale" <E.************ **@jpl.nasa.gov > wrote in message
news:cp******** **@nntp1.jpl.na sa.gov...

Bryan Bullard wrote:

Is there a standard way

No.

to validate if a pointer points to memory that was allocated by malloc?

> cat onStack.c

#include <stdio.h>
#include <stdlib.h>

int onStack(void* p) {
return (p > (void*)&p);
}

int main(int argc, char* argv[]) {
char c;
char* p = &c;
//char* p = (char*)malloc(s izeof(char));
if (onStack(p)) {
fprintf(stdout,
"p probably points to a character in automatic storage.\n");
}
else {
fprintf(stdout,
"p probably points to static data or free storage.\n");
}
return 0;
}

Actually, what I'm looking for is a way to determine if a pointer points to
a block that is "safe" to read.

[Eric Sosman]

Bryan Bullard wrote:

Bryan Bullard wrote:

Is there a standard way

[...]

Actually, what I'm looking for is a way to determine if a pointer points to
a block that is "safe" to read.

And you've been told that there's no standard way, which
is what you asked for. I've got a counter-question: If your
code is handed a junk pointer, what corrective action do you
expect it to take?

--
Er*********@sun .com

[Mark McIntyre]

On Fri, 10 Dec 2004 22:08:57 GMT, in comp.lang.c , "Bryan Bullard"
<re****@to.grou p.com> wrote:

Actually, what I'm looking for is a way to determine if a pointer points to
a block that is "safe" to read.

There is still no standard way to do this. If the block points to memory
you didn't allocate, thats a coding error. If it points to memory you
deallocated, thats also a coding error. If it points to corrupted memory,
your programme is already dead, so its too late to worry...
--
Mark McIntyre
CLC FAQ <http://www.eskimo.com/~scs/C-faq/top.html>
CLC readme: <http://www.ungerhu.com/jxh/clc.welcome.txt >

[Bryan Bullard]

"Eric Sosman" <er*********@su n.com> wrote in message
news:cp******** **@news1brm.Cen tral.Sun.COM...

I've got a counter-question: If your
code is handed a junk pointer, what corrective action do you
expect it to take?

Something more graceful then core dump.

[Bryan Bullard]

Thank you to everyone that posted.

[Mark McIntyre]

On Fri, 10 Dec 2004 22:41:41 GMT, in comp.lang.c , "Bryan Bullard"
<re****@to.grou p.com> wrote:

"Eric Sosman" <er*********@su n.com> wrote in message
news:cp******* ***@news1brm.Ce ntral.Sun.COM.. .

I've got a counter-question: If your
code is handed a junk pointer, what corrective action do you
expect it to take?

Something more graceful then core dump.

Then you're out of luck. There's no standard way to detect memory
corruption.

The question you should probably be asking is "why would I ever get a bad
pointer, if I wrote my code carefully?"
Of course from a system-specific point of view there might be either a
coding hack of some sort or a 3rd party library which trapped bad memory
and handled it. That would be a topic for a unix or windows or whatever
programming group.

--
Mark McIntyre
CLC FAQ <http://www.eskimo.com/~scs/C-faq/top.html>
CLC readme: <http://www.ungerhu.com/jxh/clc.welcome.txt >