wiretap: fix some narrowing warnings.

Make the protocol names passed to wtap_buffer_append_epdu_tag() static
arrays, so we can use sizeof to compute the string length; this should
keep at least some compilers from warning about a narrowing, as they can
determine at compile time that the length fits in 16 bits.

To prevent other warnings, make the data argument to
wtap_buffer_append_epdu_tag() const.  It's not modified, and it
*shouldn't* be modified, so make it const so that you can pass pointers
to const values to it (and so that somebody has to un-constify it if
they change wtap_buffer_append_epdu_tag() so as to break the contract).

4 files changed, 22 insertions, 11 deletions

diff --git a/wiretap/busmaster.c b/wiretap/busmaster.c
index e16dffded0..1280b202f2 100644
--- a/wiretap/busmaster.c
+++ b/wiretap/busmaster.c
@@ -62,10 +62,8 @@ busmaster_gen_packet(wtap_rec               *rec, Buffer *buf,
         || (msg->type == MSG_TYPE_EXT_RTR);
     gboolean is_err = (msg->type == MSG_TYPE_ERR);
 
-    static const char *const can_proto_name   = "can-hostendian";
-    static const char *const canfd_proto_name = "canfd";
-
-    const char        *proto_name  = is_fd ? canfd_proto_name : can_proto_name;
+    static const char can_proto_name[]   = "can-hostendian";
+    static const char canfd_proto_name[] = "canfd";
 
     if (!priv_entry)
     {
@@ -76,7 +74,14 @@ busmaster_gen_packet(wtap_rec               *rec, Buffer *buf,
 
     /* Generate Exported PDU tags for the packet info */
     ws_buffer_clean(buf);
-    wtap_buffer_append_epdu_tag(buf, EXP_PDU_TAG_DISSECTOR_NAME, (guint8 *)proto_name, strlen(proto_name));
+    if (is_fd)
+    {
+        wtap_buffer_append_epdu_tag(buf, EXP_PDU_TAG_DISSECTOR_NAME, (const guint8 *)canfd_proto_name, sizeof canfd_proto_name - 1);
+    }
+    else
+    {
+        wtap_buffer_append_epdu_tag(buf, EXP_PDU_TAG_DISSECTOR_NAME, (const guint8 *)can_proto_name, sizeof can_proto_name - 1);
+    }
     wtap_buffer_append_epdu_end(buf);
 
     if (is_fd)
diff --git a/wiretap/candump.c b/wiretap/candump.c
index f9e5242dbf..62f89e7b56 100644
--- a/wiretap/candump.c
+++ b/wiretap/candump.c
@@ -37,13 +37,19 @@ void register_candump(void);
 static void
 candump_write_packet(wtap_rec *rec, Buffer *buf, const msg_t *msg)
 {
-    static const char *can_proto_name    = "can-hostendian";
-    static const char *canfd_proto_name  = "canfd";
-    const char        *proto_name        = msg->is_fd ? canfd_proto_name : can_proto_name;
+    static const char can_proto_name[]   = "can-hostendian";
+    static const char canfd_proto_name[] = "canfd";
 
     /* Generate Exported PDU tags for the packet info */
     ws_buffer_clean(buf);
-    wtap_buffer_append_epdu_tag(buf, EXP_PDU_TAG_DISSECTOR_NAME, (guint8 *)proto_name, strlen(proto_name));
+    if (msg->is_fd)
+    {
+        wtap_buffer_append_epdu_tag(buf, EXP_PDU_TAG_DISSECTOR_NAME, (const guint8 *)canfd_proto_name, sizeof canfd_proto_name - 1);
+    }
+    else
+    {
+        wtap_buffer_append_epdu_tag(buf, EXP_PDU_TAG_DISSECTOR_NAME, (const guint8 *)can_proto_name, sizeof can_proto_name - 1);
+    }
     wtap_buffer_append_epdu_end(buf);
 
     if (msg->is_fd)
diff --git a/wiretap/wtap.c b/wiretap/wtap.c
index 7c6752b6ec..387406189a 100644
--- a/wiretap/wtap.c
+++ b/wiretap/wtap.c
@@ -1934,7 +1934,7 @@ wtap_full_file_seek_read(wtap *wth, gint64 seek_off, wtap_rec *rec, Buffer *buf,
 }
 
 void
-wtap_buffer_append_epdu_tag(Buffer *buf, guint16 epdu_tag, guint8 *data, guint16 data_len)
+wtap_buffer_append_epdu_tag(Buffer *buf, guint16 epdu_tag, const guint8 *data, guint16 data_len)
 {
 	guint8 pad_len = 0;
 	guint space_needed = 4; /* 2 for tag field, 2 for length field */
diff --git a/wiretap/wtap.h b/wiretap/wtap.h
index 90a2aa72e4..804329a7d4 100644
--- a/wiretap/wtap.h
+++ b/wiretap/wtap.h
@@ -2222,7 +2222,7 @@ gboolean wtap_dump_can_write(const GArray *file_encaps, guint32 required_comment
  * @param data_len      length of data
  */
 WS_DLL_PUBLIC
-void wtap_buffer_append_epdu_tag(Buffer *buf, guint16 epdu_tag, guint8 *data, guint16 data_len);
+void wtap_buffer_append_epdu_tag(Buffer *buf, guint16 epdu_tag, const guint8 *data, guint16 data_len);
 
 /**
  * Generates packet data for an unsigned integer in "exported PDU" format.