Use explicit_bzero where it makes sense

PVS studio new report, warning type V597

Change-Id: Icd85aadf3ffc587806f9a24d224d0a369d4ce0e0
Reviewed-on: https://review.haiku-os.org/c/1594
Reviewed-by: waddlesplash <[email protected]>

src/add-ons/kernel/file_systems/userlandfs/server/beos/Jamfile

@@ -12,6 +12,8 @@ SubDirSysHdrs [ FDirName $(userlandFSIncludes) ] ;
 SubDirHdrs [ FDirName $(userlandFSIncludes) private ] ;
 SubDirHdrs [ FDirName $(userlandFSIncludes) shared ] ;
 
+UseHeaders [ FDirName $(HAIKU_TOP) headers compatibility bsd ] : true ;
+
 SEARCH_SOURCE += [ FDirName $(userlandFSTop) private ] ;
 SEARCH_SOURCE += [ FDirName $(userlandFSTop) shared ] ;
 
@@ -31,5 +33,5 @@ SharedLibrary libuserlandfs_beos_kernel.so
 
 	:
 	<nogrist>userlandfs_server
-	[ TargetLibsupc++ ]
+	[ TargetLibsupc++ ] bsd
 ;

src/add-ons/kernel/file_systems/userlandfs/server/beos/fs_cache.c

@@ -36,6 +36,8 @@
    [email protected]
 */
 
+#define _BSD_SOURCE
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <memory.h>
@@ -1075,7 +1077,7 @@ delete_cache_list(cache_ent_list *cel)
                    "%p != %p\n", ce->block_num, junk, ce);
         }
 
-        memset(ce, 0xfd, sizeof(*ce));
+        explicit_bzero(ce, sizeof(*ce));
         free(ce);
 
         bc.cur_blocks--;

src/system/libnetwork/netresolv/dst/dst_api.c

@@ -909,11 +909,11 @@ dst_s_read_private_key_file(char *name, DST_KEY *pk_key, u_int16_t in_id,
 	}
 	pk_key->dk_id = (u_int16_t) id;
 	pk_key->dk_alg = alg;
-	memset(in_buff, 0, cnt);
+	explicit_bzero(in_buff, cnt);
 	return (1);
 
  fail:
-	memset(in_buff, 0, cnt);
+	explicit_bzero(in_buff, cnt);
 	return (0);
 }
 

src/system/libnetwork/netresolv/dst/dst_internal.h

@@ -72,8 +72,8 @@ typedef struct dst_key {
 
 #ifndef SAFE_FREE
 #define SAFE_FREE(a) \
-do{if(a != NULL){memset(a,0, sizeof(*a)); free(a); a=NULL;}} while (0)
-#define SAFE_FREE2(a,s) if (a != NULL && (long)s > 0){memset(a,0, s);free(a); a=NULL;}
+do{if(a != NULL){explicit_bzero(a, sizeof(*a)); free(a); a=NULL;}} while (0)
+#define SAFE_FREE2(a,s) if (a != NULL && (long)s > 0){explicit_bzero(a, s);free(a); a=NULL;}
 #endif
 
 typedef struct dst_func {