flood of warnings building dlmalloc_ext_2_8_6.c on clang11

[vinniefalco]

From https://travis-ci.com/github/vinniefalco/json/jobs/420747907#L894

In file included from libs/container/src/alloc_lib.c:24:
In file included from libs/container/src/dlmalloc_ext_2_8_6.c:38:
libs/container/src/dlmalloc_2_8_6.c:3228:53: warning: arithmetic on a null pointer treated as a cast from integer to pointer is a GNU extension [-Wnull-pointer-arithmetic]
  assert(sz == ((sp->base + sp->size) - (char*)p) - TOP_FOOT_SIZE);
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~
libs/container/src/dlmalloc_2_8_6.c:2729:17: note: expanded from macro 'TOP_FOOT_SIZE'
  (align_offset(chunk2mem(0))+pad_request(sizeof(struct malloc_segment))+MIN_CHUNK_SIZE)
                ^
libs/container/src/dlmalloc_2_8_6.c:2216:55: note: expanded from macro 'chunk2mem'
#define chunk2mem(p)        ((void*)((char*)(p)       + TWO_SIZE_T_SIZES))
                                                      ^
libs/container/src/dlmalloc_2_8_6.c:1620:14: note: expanded from macro 'align_offset'
 ((((size_t)(A) & CHUNK_ALIGN_MASK) == 0)? 0 :\
             ^
libs/container/src/dlmalloc_2_8_6.c:1444:24: note: expanded from macro 'assert'
#define assert(x) if(!(x)) ABORT
                       ^
libs/container/src/dlmalloc_2_8_6.c:3228:53: warning: arithmetic on a null pointer treated as a cast from integer to pointer is a GNU extension [-Wnull-pointer-arithmetic]
  assert(sz == ((sp->base + sp->size) - (char*)p) - TOP_FOOT_SIZE);
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~
libs/container/src/dlmalloc_2_8_6.c:2729:17: note: expanded from macro 'TOP_FOOT_SIZE'
  (align_offset(chunk2mem(0))+pad_request(sizeof(struct malloc_segment))+MIN_CHUNK_SIZE)
                ^
libs/container/src/dlmalloc_2_8_6.c:2216:55: note: expanded from macro 'chunk2mem'
#define chunk2mem(p)        ((void*)((char*)(p)       + TWO_SIZE_T_SIZES))
                                                      ^
libs/container/src/dlmalloc_2_8_6.c:1621:34: note: expanded from macro 'align_offset'
  ((MALLOC_ALIGNMENT - ((size_t)(A) & CHUNK_ALIGN_MASK)) & CHUNK_ALIGN_MASK))
                                 ^
libs/container/src/dlmalloc_2_8_6.c:1444:24: note: expanded from macro 'assert'
#define assert(x) if(!(x)) ABORT
                       ^
libs/container/src/dlmalloc_2_8_6.c:3422:25: warning: arithmetic on a null pointer treated as a cast from integer to pointer is a GNU extension [-Wnull-pointer-arithmetic]
    sum += m->topsize + TOP_FOOT_SIZE;

[igaztanaga]

Thanks for the report. I don't have access to clang 11, please report if the commit does not fix all the warnings.

[vinniefalco]

Looks good now! See: https://travis-ci.com/github/vinniefalco/json/jobs/423314334