Report syntax errors in UAT prefs parsing

Add the cause for a syntax error while parsing UATs. Example output:

    $ tshark -ouat:ssl_keys:,
    tshark: Invalid -o flag "uat:ssl_keys:,": ssl_keys:1: No IP address given.
    $ tshark -ouat:unknown:,
    tshark: Invalid -o flag "uat:unknown:,": Unknown preference

Change-Id: I549406c4e31a81d29f487ef47bdb3c22da084947
Reviewed-on: https://code.wireshark.org/review/21748
Petri-Dish: Peter Wu <peter@lekensteyn.nl>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Jakub Zawadzki <darkjames-ws@darkjames.pl>
Reviewed-by: Michael Mann <mmann78@netscape.net>

2 files changed, 19 insertions, 15 deletions

diff --git a/epan/prefs.c b/epan/prefs.c
index 18fdc15c31..35ff3fa2a2 100644
--- a/epan/prefs.c
+++ b/epan/prefs.c
@@ -4510,10 +4510,9 @@ read_prefs_file(const char *pf_path, FILE *pf,
  * a valid uat entry.
  */
 static gboolean
-prefs_set_uat_pref(char *uat_entry) {
+prefs_set_uat_pref(char *uat_entry, char **errmsg) {
     gchar *p, *colonp;
     uat_t *uat;
-    gchar *err = NULL;
     gboolean ret;
 
     colonp = strchr(uat_entry, ':');
@@ -4543,11 +4542,11 @@ prefs_set_uat_pref(char *uat_entry) {
     uat = uat_find(uat_entry);
     *colonp = ':';
     if (uat == NULL) {
+        *errmsg = g_strdup("Unknown preference");
         return FALSE;
     }
 
-    ret = uat_load_str(uat, p, &err);
-    g_free(err);
+    ret = uat_load_str(uat, p, errmsg);
     return ret;
 }
 
@@ -4558,7 +4557,7 @@ prefs_set_uat_pref(char *uat_entry) {
  * in some fashion.
  */
 prefs_set_pref_e
-prefs_set_pref(char *prefarg)
+prefs_set_pref(char *prefarg, char **errmsg)
 {
     gchar *p, *colonp;
     prefs_set_pref_e ret;
@@ -4573,6 +4572,8 @@ prefs_set_pref(char *prefarg)
     mgcp_tcp_port_count = -1;
     mgcp_udp_port_count = -1;
 
+    *errmsg = NULL;
+
     colonp = strchr(prefarg, ':');
     if (colonp == NULL)
         return PREFS_SET_SYNTAX_ERR;
@@ -4599,7 +4600,7 @@ prefs_set_pref(char *prefarg)
     if (strcmp(prefarg, "uat")) {
         ret = set_pref(prefarg, p, NULL, TRUE);
     } else {
-        ret = prefs_set_uat_pref(p) ? PREFS_SET_OK : PREFS_SET_SYNTAX_ERR;
+        ret = prefs_set_uat_pref(p, errmsg) ? PREFS_SET_OK : PREFS_SET_SYNTAX_ERR;
     }
     *colonp = ':';    /* put the colon back */
     return ret;
diff --git a/epan/prefs.h b/epan/prefs.h
index 85d66b6cf6..e757a25533 100644
--- a/epan/prefs.h
+++ b/epan/prefs.h
@@ -575,14 +575,8 @@ extern e_prefs *read_prefs(void);
    into "*pf_path_return", and return the errno. */
 WS_DLL_PUBLIC int write_prefs(char **);
 
-/*
- * Given a string of the form "<pref name>:<pref value>", as might appear
- * as an argument to a "-o" option, parse it and set the preference in
- * question.  Return an indication of whether it succeeded or failed
- * in some fashion.
- *
- * XXX - should supply, for syntax errors, a detailed explanation of
- * the syntax error.
+/**
+ * Result of setting a preference.
  */
 typedef enum {
     PREFS_SET_OK,               /* succeeded */
@@ -591,7 +585,16 @@ typedef enum {
     PREFS_SET_OBSOLETE          /* preference used to exist but no longer does */
 } prefs_set_pref_e;
 
-WS_DLL_PUBLIC prefs_set_pref_e prefs_set_pref(char *prefarg);
+/*
+ * Given a string of the form "<pref name>:<pref value>", as might appear
+ * as an argument to a "-o" option, parse it and set the preference in
+ * question.  Return an indication of whether it succeeded or failed
+ * in some fashion.
+ *
+ * For syntax errors (return value PREFS_SET_SYNTAX_ERR), details (when
+ * available) are written into "errmsg" which must be freed with g_free.
+ */
+WS_DLL_PUBLIC prefs_set_pref_e prefs_set_pref(char *prefarg, char **errmsg);
 
 /*
  * Get or set a preference's obsolete status. These can be used to make a