smap output - unnamed entries and heap

Hi All,

My apologies if this is not the right place for these type of
questions - I do not know of a better place to ask this.

I am trying to take out some memory figures from the /proc/<pid>/smaps
interface (linux v2.6.35). However, I could not find what do the
entries that have no name associated to them (no library path or
binary path with these entries) mean. So, I wrote a test C program
that allocates 100MB of memory (using malloc) and then writes to it in
chunks of 10MB. I could see that the 'Size' and 'RSS' of one of the
unnamed entries was increasing in accordance with the code, but there
were several other such unnamed sections too - is there a way to know
what and where do they come from.

Also, I could see that for some process the smap interface was showing
a '[heap]' entry but not for all - e.g. for my above test case, there
was no '[heap]' entry, although I assumed the malloc should have
reflected in the [heap]. Can someone please tell me (or point me in
the right direction) why is heap entry there only for some processes ?

Thanks in advance for any help..

Regards,
Aneesh Bhasin