C++ pointers

[AJ]

//C++

char* p;

while (*p)
{}

/* Access violation. How can I check to see if p is valid? Thanks.*/

[Victor Bazarov]

AJ wrote:

//C++

char* p;

while (*p)
{}

/* Access violation. How can I check to see if p is valid? Thanks.*/

There is no compiler- or platform-independent way to check that
a pointer is "valid". Besides, what's your definition of pointer
validity? And what it is you're trying to do in that code?

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

[Default User]

AJ wrote:

//C++

char* p;

while (*p)
{}

/* Access violation. How can I check to see if p is valid? Thanks.*/

You can check to see if it's a null pointer, but beyond that there's
nothing standard you can do for an uninitialized or deleted pointer.

Brian

[Frederick Gotham]

AJ posted:

//C++

char* p;

while (*p)
{}

/* Access violation. How can I check to see if p is valid? Thanks.*/

You check to see if it's valid by opening up your favourite text editor
and going through your code to see when and where you gave it a value (if
you did).

In C++, you can give a pointer a particular value to indicate that it
doesn't really point to anything. This is called the null pointer value.
Here's a taste of it:

char *p = 0;

if (p) DoSomethingWithAddress(p);
If you define a variable within a function without initialising it (and
without subsequently setting its value), then it contains white noise --
and therefore you can't rely on it having the "null pointer value"... it
may in fact point to a boolean value stored in memory which decides if
your hard disk should be formatted.

[Vaclav Haisman]

AJ wrote, On 21.6.2006 21:10:

//C++

char* p;

while (*p)
{}

/* Access violation. How can I check to see if p is valid? Thanks.*/

Use valgrind or some other platform specific tool.

--
VH

[Jerry Coffin]

In article <1150917030.618581.196250
@m73g2000cwd.googlegroups.com>, aj********@yahoo.com
says...

//C++

char* p;

while (*p)
{}

/* Access violation. How can I check to see if p is valid? Thanks.*/

There is no portable way to check whether a pointer is
valid. For that matter, there's no portable definition of
what constitutes a valid pointer in the first place.

One obvious alterative is to use smart pointer class of
some sort instead of using a raw pointer to start with.
The smart pointer class can include code to check whether
its pointer has been initialized or (more common)
initialize its pointer so it's always been assigned a
value. Of course, this still isn't a panacea -- if you do
something equivalent to:

char *p = (char *)1;

chances are you'll end up with a pointer that's still
invalid -- but for that to happen, you have to do it
explicitly, rather than it happening by default.

--
Later,
Jerry.

The universe is a figment of its own imagination.

[Jim Langston]

"AJ" <aj********@yahoo.com> wrote in message
news:11**********************@m73g2000cwd.googlegr oups.com...

//C++

char* p;

while (*p)
{}

/* Access violation. How can I check to see if p is valid? Thanks.*/

char* p = NULL;

while ( p != NULL && *p )
{
}