alt Hacker News> Noncompliant, since `malloc(0)` is specified to return a unique pointer if it's not `NULL`.
I know I've seen that somewhere, but may I ask what standard you're referring to?
If I recall correctly, this was an archaic stackless microcontroller. The heap support was mostly a marketing claim.
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(you duped your comment under the other subthread)
From C89, §7.10.3 "Memory management functions":
> If the size of the space requested is > zero, the behavior is implementation-defined; the value returned shall be either a null pointer or a > unique pointer.
The wording is different for C99 and POSIX, but I went back as far as possible (despite the poor source material; unlike later standards C89 is only accessible in scans and bad OCR, and also has catastrophic numbering differences). K&R C specifies nothing (it's often quite useless; people didn't actually write against K&R C but against the common subset of extensions of platforms they cared about), but its example implementation adds a block header without checking for 0 so it ends up doing the "unique non-NULL pointer" thing.
Presumably the ANSI C standard or one of the later editions? They also cover the standard library as well as the language. (Presumably the bit about "Each such allocation shall yield a pointer to an object disjoint from any other object." if the random C99 draft I found via google is accurate to the final standard - I suppose you might question if this special use is technically an allocation of course).
Of course, microcontrollers and the like can have somewhat eccentric implementations of languages of thing and perhaps aren't strictly compliant, and frankly even standard compliant stuff like "int can be 16 bits" might surprise some code that doesn't expect it.
C89: https://port70.net/%7Ensz/c/c89/c89-draft.html
If the size of the space requested is zero, the behavior is implementation-defined; the value returned shall be either a null pointer or a unique pointer.