RE: Function to see if a pointer is on the stack

You should be able to easily wrap the thread creation functions
to initialize thread-local data for the "isonstack" call. You
could also add a grep for thread creation to your checkin tests
to make sure nobody breaks the rule (make sure to exempt the
actual wrapper implementation, though :-)

Sadly, the Platform SDK doesn't have a function to test whether
something is on a stack or not -- in fact, there isn't even a
function to query the stack extent of a specific thread, only
the current stack pointer! (By getting the CONTEXT structure)
This has annoyed me in the past, but if you're Windows specific,
the creation wrapping and Tls / Fls stack base works pretty
well.

Cheers,

			/ h+


-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of
Jacob Turner (Core Design Ltd)
Sent: Friday, August 20, 2004 4:29 AM
To: [email protected]
Subject: RE: [GD-Windows] Function to see if a pointer is on the stack


Unfortunately can't do the reliable method.  My example for copying strings
is just an example so can't use std::string<> or bare pointer technique.

Bit scared about the other option because we are in a multi-threaded app and
this function would be common to all threads and we don't have explicit
creation of common library stuff when a new thread is made.

Isn't there a really PC specific code e.g. getting the stack ptr etc.  This
is how I am doing the function on consoles.

Mind you not a big hassle because on the PC we have so much memory that
don't care if just always copy strings or whatever data i.e. can make is
variable on stack function return TRUE all the time.

Thanks

Jake

> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]]On Behalf Of
> Jon Watte
> Sent: 19 August 2004 18:19
> To: [email protected]
> Subject: RE: [GD-Windows] Function to see if a pointer is on the stack
>
>
> The most reliable way of doing this is to use a class for
> your argument rather than bare pointers, and have a
> constructor from bare pointers, and use reference counting
> in the class implementation -- this is almost exactly what
> std::string<> already does for you!
>
> Else, you can register the stack pointer in main() (or the
> entry function for each thread/fiber), and get the stack
> pointer in the called function, and compare -- this is not
> entirely portable, because the stack may grow up on some
> architectures.
>
> // non-threaded version -- if you use threads or fibers,
> // you need one gBase per thread/fiber
>
> char * gBase;
>
> void register_main( char * base ) {
>   gBase = base;
> }
>
> bool is_stack_pointer( char const * ptr ) {
>   char top[10];
>   assert( top < gBase ); // else stack grows up
>   return (ptr < gBase) && (ptr > top);
> }
>
> int main() {
>   ...
>   char junk[ 10 ];
>   register_main( junk );
>   ...
> }
>
> void some_func( char * anArg ) {
>   if( is_stack_pointer( anArg ) ) {
>     ...
>   }
> }
>
>
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]]On Behalf Of
> Jacob Turner (Core Design Ltd)
> Sent: Thursday, August 19, 2004 9:30 AM
> To: [email protected]
> Subject: [GD-Windows] Function to see if a pointer is on the stack
>
>
> Is there some simple and reliable code for a console or
> windows app to test
> if a pointer value is on the stack or not ?
>
> If the pointer is on the stack (e.g. a string) then we want
> to copy the
> string to heap memory for reuse later on.
>
> Cheers
>
> Jake
>
>
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