In file hiredis.c,line 1126,the function sdsempty is called and its return value can be null,so c->obuf can be a null pointer.Then, in
file hiredis.c,line 1132,function sdslen is called and c->obuf is the first parameter.In file sds.h,line 48,function sdslen,s is derefered without check if it is null pointer.step graph is showed bellow.
