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malloc is special in environments that aren't free-standing, the compiler can assume that the pointer that malloc returns doesn't alias any other at that point.

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Though with most compilers, there are ways of making other functions similarly special.

I am not familiar with 'free-standing', though, I think that malloc in most environments never returns the same pointer twice (an alias). Though I may misunderstand your point.

C++11 1.4 [intro.compliance]/p7 "A freestanding implementation is one in which execution may take place without the benefit of an operating system, and has an implementation-deﬁned set of libraries that includes certain language-support libraries" [1]

C11 4 [conformance]/p6 "A conforming freestanding implementation shall accept any strictly conforming program in which the use of the features speciﬁed in the library clause (clause 7) is conﬁned to the contents of the standard headers <float.h>, <iso646.h>, <limits.h>, <stdalign.h>, <stdarg.h>, <stdbool.h>, <stddef.h>, <stdint.h>, and <stdnoreturn.h>." [2]

[1] http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n324... [2] http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf

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