Help with malloc

[Matthew Woehlke]

Vardhan, Sundara (GE Infra, Energy) wrote:
> 	Desperate: Do not know if this is the right forum for this
> question. Using gcc 4.1.1 on Red Hat Linux, I keep getting negative
> pointer value when I try to allocate more than 128000 bytest using
> malloc(). Works fine if the value is less than 128000. Any ideas why
> this happens. I would very much appreciate your help and input.

It sounds like a: a misconception on your part (what is a "negative 
pointer" and why do you think this is a problem?), and b: a boundary 
across which malloc() uses the heap vs. doing a mmap().

Probably you are confusing "negative" for the address space 0x80000000 - 
0xFFFFFFFF, the heap lives below this, and 128000 (probably the actual 
value is closer to 131072 == 128 KiB, perhaps a bit less for 
heap-related structures hanging off one of the ends of the block) is the 
threshold for mmap() vs. heap allocation. So smaller requests come from 
the heap, and larger ones are mmap()d (incidentally from the 0x80000000 
- 0xFFFFFFFF range on your OS).

...and a glibc (or newlib, or whoever provides your libc) forum/list is 
probably more appropriate :-).

-- 
Matthew
Please do not quote my e-mail address unobfuscated in message bodies.
-- 
C++ is for people who want to be able to not just shoot themselves in 
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