malloc(0)
malloc(0)
Posted Jan 31, 2022 1:20 UTC (Mon) by jreiser (subscriber, #11027)In reply to: Handling argc==0 in the kernel by NYKevin
Parent article: Handling argc==0 in the kernel
>It is legal to call malloc(0), and it is legal for malloc(0) to return a value other than NULL. If it does so, then the only thing you're allowed to do with that value is pass it to free()
One of the uses of malloc(0) is to serve as an analogue of the Lisp function (gensym): return a unique value, one that does not point to anything else returned by malloc, both now and for the remaining life of the process. (Yes, the standard requires this.) An implementation for which malloc(0) always returns NULL is not acceptable. So in practice, many implementations begin with something like size += (0==size), i.e. malloc(0) is treated as malloc(1).
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