[GitHub] [nuttx] xiaoxiang781216 commented on pull request #9143: mm: malloc return valid pointer when request 0 size

["xiaoxiang781216 (via GitHub)" <gi...@apache.org>]

xiaoxiang781216 commented on PR #9143:
URL: https://github.com/apache/nuttx/pull/9143#issuecomment-1529390428

   Most popular implementation list in https://en.wikipedia.org/wiki/C_standard_library returns non-NULL pointer for malloc(0):
   https://github.com/bminor/glibc/blob/master/malloc/malloc.c#L115-L116
   https://github.com/huangqinjin/ucrt/blob/master/heap/malloc_base.cpp#L29
   https://github.com/bminor/musl/blob/master/src/malloc/lite_malloc.c#L50
   https://github.com/bminor/newlib/blob/master/newlib/libc/stdlib/_mallocr.c#L1420-L1423
   https://github.com/picolibc/picolibc/blob/main/newlib/libc/stdlib/mallocr.c#L109-L110
   https://github.com/jemalloc/jemalloc/blob/dev/src/jemalloc.c#L2305-L2329
   
   Two give user compile time choice:
   https://github.com/ensc/dietlibc/blob/master/lib/alloc.c#L155-L159
   https://git.uclibc.org/uClibc/tree/libc/stdlib/malloc/malloc.c#n211
   
   Only one return NULL:
   https://kernel.googlesource.com/pub/scm/libs/klibc/klibc.git/+/refs/heads/master/usr/klibc/malloc.c
   
   So, many applications may implicitly depend on that malloc(0) return non-NULL pointer without caution. 
   My question is that:
   
   1. The standard explicitly states that it's a legal implementation that malloc(0) return non-NULL pointer
   2. Most popular libc implementation return non-NULL for malloc(0)
   3. There is no bad side effect to return non-NULL pointer for malloc(0)
   4. Many applications depends on this behavior
   
   What's the benefit to return NULL pointer when user call malloc with zero?


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