malloc question

[Andy Lieberman]

I want to write a function that will return the size of a memory
block that was allocated with malloc.  How can I determine this
knowing only the pointer to the start of the block? (I know I
could keep track myself, but I don't see why I should have to.)
I'm using SUNOS 3.5.  

Please reply by e-mail and I will post a summary.

Thanks,
Andy Lieberman
andy at library.Berkeley.EDU