Description of problem:


Version-Release number of selected component (if applicable):
rpm -qf /usr/include/samba-4.0/ndr.h 
samba-devel-4.10.0-0.0.rc1.fc30.x86_64

How reproducible:
Deterministic

Steps to Reproduce:
1. dnf install -y gcc samba-devel pkgconf-pkg-config
2. cat >test.c <<EOF
#include <ndr.h>

#define ZERO_STRUCT(x) cool_function((char *)&(x), sizeof(x), 0, sizeof(x))

int main(void) {
    return 0;
}
EOF
3. gcc `pkg-config --cflags ndr` pok.c

Actual results:
pok.c:3: warning: "ZERO_STRUCT" redefined
    3 | #define ZERO_STRUCT(x) memset((char *)&(x), sizeof(x), 0, sizeof(x))
      | 
In file included from /usr/include/samba-4.0/ndr.h:29,
                 from pok.c:1:
/usr/include/samba-4.0/util/memory.h:54: note: this is the location of the previous definition
   54 | #define ZERO_STRUCT(x) memset_s((char *)&(x), sizeof(x), 0, sizeof(x))
      |

Expected results:
No warnings are generated.

Additional info:

I assume that the header file /usr/include/samba-4.0/util/memory.h is public because the macro discard_const (defined in util/memory.h) is used in another macro in ndr.h

sh$ grep -n -C5 discard_const /usr/include/samba-4.0/ndr.h 
373-#define NDR_PULL_SET_MEM_CTX(ndr, mem_ctx, flgs) do {\
374-    if ( !(flgs) || (ndr->flags & flgs) ) {\
375-            if (!(mem_ctx)) {\
376-                    return ndr_pull_error(ndr, NDR_ERR_ALLOC, "NDR_PULL_SET_MEM_CTX(NULL): %s\n", __location__); \
377-            }\
378:            ndr->current_mem_ctx = discard_const(mem_ctx);\
379-    }\
380-} while(0)
381-
382-#define _NDR_PULL_FIX_CURRENT_MEM_CTX(ndr) do {\
383-    if (!ndr->current_mem_ctx) {\


Making macros without any prefix is not idea way. People will need to undefine then and then define with different content.