On Friday, October 22, 2010 02:10:16 Joakim Tjernlund wrote:
Mike Frysinger wrote on 2010/10/21 21:51:53:
it is useful for malloc(0) == NULL. the glibc behavior is downright obnoxious. we disable this for uClibc and dont see problems. if anything, we catch accidental programming mistakes which then get fixed.
There is a value in having the possibility to express a 0 bytes data set. Consider this simple example: An app read lines from a file and mallocs each line read and builds an array with malloced pointers. The last entry is a NULL ptr to signal EOF. This breaks down for empty lines if malloc(0) returns NULL.
i dont think so ... C strings are always at least one byte, so an empty line would be malloc(1)
Not to mention error handling, as I recall, a malloc(0) that returns NULL does not set errno which screws error handling. One have to bend over just to cope with this.
that depends on your implementation. in u-boot, there really is no "errno" concept. but i dont see how this matters as i dont see any example in u-boot context where malloc(0) is a problem.
why exactly do you want malloc(0) to return valid memory ? i would rather have u-boot return an error.
Ideally it should return a ptr to invalid memory so you get a SEGV if you try to defer the ptr but I take anything over a NULL ptr.
the concept of an invalid pointer is pretty arch-specific. and it changes the semantics of what the vast majority of coders (and their code) out there expect -- NULL means error while non-NULL means success.
a better question might be "why isnt a NULL pointer on your platform an invalid pointer" ? ive added a simple CONFIG define for Blackfin users to do just that -- make access to the low 1KiB of memory generate an exception. it does so with pretty much 0 runtime overhead. -mike