Re: stack sizes, Segments

On Thu, 23 Jan 2025 1:07:02 +0000, Scott Lurndal wrote:

Michael S <already5chosen@yahoo.com> writes:

On Wed, 22 Jan 2025 15:01:34 GMT
scott@slp53.sl.home (Scott Lurndal) wrote:
>

Michael S <already5chosen@yahoo.com> writes:

On Wed, 22 Jan 2025 02:54:33 -0000 (UTC)
John Levine <johnl@taugh.com> wrote:
>

According to George Neuner  <gneuner2@comcast.net>:

Not standard compliant for sure, but you certainly can approximate
stack use in C:  just store (as byte*) the address of a local in
your top level function, and check the (absolute value of) the
difference to the address of a local in the current function.

>
Ugh, but yes that would work with the usual stack structure,
>

The bigger problem is knowing how much stack is available to use -
there may be no way (or no easy way) to find the actual size ...
or the limit if the stack expands ... and circumstances beyond the
program may have limited it to be smaller than the program
requested.

>
There's often no way to tell since it may depend on things like
running out of swap space which depends on how much memory other
programs are using.
>

>
At least you can know the size of reserved VA space which is both an
upper bound of the limit and in 99% of the cases an actual limit.
>
On Windows:
https://learn.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-getcurrentthreadstacklimits
>
I suppose that similar functions are available on other OSes as well.
>

>
https://pubs.opengroup.org/onlinepubs/9799919799/functions/pthread_attr_getstack.html
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There is no equivlent function for the main process stack,

>
>
Do you mean "there is no equivlent *POSIX* function", right?
But I sincerily hope that most Unix-like systems provide such
functionality in system-specific manner. Because it looks usable.

>
What would an application (portable or otherwise) use the process
stack base address for?

As a place to put TLS (or &TLS) on register-starved architectures.