When the return type of the function is int, it's better to return an

in than NULL, especially when an error is signalled with a negative
value.

crypto/dso/dso_lib.c

@@ -472,7 +472,7 @@ int DSO_pathbyaddr(void *addr,char *path,int sz)
 	if (meth->pathbyaddr == NULL)
 		{
 		DSOerr(DSO_F_PATHBYADDR,DSO_R_UNSUPPORTED);
-		return(NULL);
+		return -1;
 		}
 	return (*meth->pathbyaddr)(addr,path,sz);
 	}