Question

malloc defined like below:

void *malloc(size_t size);

http://pubs.opengroup.org/onlinepubs/009695399/functions/malloc.html

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size_t definition (stddef.h):

size_t: Unsigned integer type of the result of the sizeof operator.
http://pubs.opengroup.org/onlinepubs/009604499/basedefs/stddef.h.html

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But according this page, max limitation of size_t is 65535.
(Section Limits of Other Integer Types):

Limit of size_t: SIZE_MAX 65535
http://pubs.opengroup.org/onlinepubs/007904975/basedefs/stdint.h.html

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Does it mean I can not allocate more than 65535 bytes when I want to respect C standard?

Answer 1

SIZE_MAX must be at least 65535. If you’re running something like MS-DOS, chances are it’ll actually even be that small. On a typical, reasonably current desktop computer (say, anything less than 10 years old) you can expect it to be larger, typically at least around 4 billion (2³²-1, to be more exact).

Whether you need to (try to) deal with a more limited system will depend on the range of targets to which you might care about porting your code. If you really might need to deal with a 16-bit compiler on a system with less than, say, 1 megabyte of addressable memory, then you’ll have to write your code with that in mind. In all honesty, however, for most people that’s simply irrelevant — even relatively small portable systems (e.g., an iPod) can address far more memory than that any more. OTOH, if you’re writing code for a singing greeting card, then yes, such limitations probably come with the territory (but in such cases, the standard is often something to treat more as a general guideline than an absolute law).