dfilter: Handle missing error location more gracefully

If we don't have an offset, don't print anything with underline.

Also it can underline filters using macros correctly now.

$ tshark -Y 'ip and ${private_ipv4:ip.sr}' -r /dev/null
tshark: Left side of "==" expression must be a field or function, not "ip.sr".
    ip and ip.sr == 192.168.0.0/16 or ip.sr == 172.16.0.0/12 or ip.sr == 10.0.0.0/8
           ^~~~~

dftest.c

@@ -167,9 +167,11 @@ main(int argc, char **argv)
     if (!dfilter_compile_real(expanded_text, &df, &err_msg, &err_loc,
                                                 "dftest", TRUE, FALSE)) {
         fprintf(stderr, "dftest: %s\n", err_msg);
-        fprintf(stderr, "\t%s\n", expanded_text);
-        fputc('\t', stderr);
-        putloc(stderr, err_loc.col_start, err_loc.col_len);
+        if (err_loc.col_start >= 0) {
+            fprintf(stderr, "\t%s\n", expanded_text);
+            fputc('\t', stderr);
+            putloc(stderr, err_loc.col_start, err_loc.col_len);
+        }
         g_free(err_msg);
         g_free(expanded_text);
         epan_cleanup();

epan/dfilter/dfilter.c

@@ -58,6 +58,10 @@ dfilter_vfail(dfwork_t *dfw, stloc_t *loc,
 	if (loc) {
 		dfw->err_loc = *loc;
 	}
+	else {
+		dfw->err_loc.col_start = -1;
+		dfw->err_loc.col_len = 0;
+	}
 }
 
 void

epan/dfilter/syntax-tree.c

@@ -304,6 +304,8 @@ sprint_node(stnode_t *node)
 	wmem_strbuf_append_printf(buf, "magic=0x%"PRIx32", ", node->magic);
 	wmem_strbuf_append_printf(buf, "type=%s, ", stnode_type_name(node));
 	wmem_strbuf_append_printf(buf, "data=<%s>, ", stnode_todebug(node));
+	wmem_strbuf_append_printf(buf, "location=%d:%zu",
+			node->location.col_start, node->location.col_len);
 	return wmem_strbuf_finalize(buf);
 }
 

tshark.c

@@ -606,6 +606,40 @@ gather_tshark_runtime_info(feature_list l)
     epan_gather_runtime_info(l);
 }
 
+static gboolean
+_compile_dfilter(const char *text, dfilter_t **dfp, const char *caller)
+{
+    gboolean ok;
+    dfilter_loc_t err_loc;
+    char *err_msg = NULL;
+    char *err_off;
+    char *expanded;
+
+    expanded = dfilter_expand(text, &err_msg);
+    if (expanded == NULL) {
+        cmdarg_err("%s", err_msg);
+        g_free(err_msg);
+        return FALSE;
+    }
+
+    ok = dfilter_compile_real(expanded, dfp, &err_msg, &err_loc, caller, FALSE, FALSE);
+    if (!ok ) {
+        cmdarg_err("%s", err_msg);
+        g_free(err_msg);
+        if (err_loc.col_start >= 0) {
+            err_off = ws_strdup_error_offset(NULL, err_loc.col_start, err_loc.col_len);
+            cmdarg_err_cont("    %s", expanded);
+            cmdarg_err_cont("    %s", err_off);
+            g_free(err_off);
+        }
+    }
+
+    g_free(expanded);
+    return ok;
+}
+
+#define compile_dfilter(text, dfp)      _compile_dfilter(text, dfp, __func__)
+
 static void
 about_folders(void)
 {
@@ -722,7 +756,7 @@ must_do_dissection(dfilter_t *rfcode, dfilter_t *dfcode,
 int
 main(int argc, char *argv[])
 {
-    char                *err_msg, *err_msg_cont;
+    char                *err_msg;
     static const struct report_message_routines tshark_report_routines = {
         failure_message,
         failure_message,
@@ -777,7 +811,6 @@ main(int argc, char *argv[])
     gchar               *volatile dfilter = NULL;
     dfilter_t           *rfcode = NULL;
     dfilter_t           *dfcode = NULL;
-    dfilter_loc_t       df_loc;
     e_prefs             *prefs_p;
     gchar               *output_only = NULL;
     gchar               *volatile pdu_export_arg = NULL;
@@ -2014,12 +2047,7 @@ main(int argc, char *argv[])
 
     if (rfilter != NULL) {
         ws_debug("Compiling read filter: '%s'", rfilter);
-        if (!dfilter_compile2(rfilter, &rfcode, &err_msg, &df_loc)) {
-            cmdarg_err("%s", err_msg);
-            err_msg_cont = ws_strdup_error_offset(NULL, df_loc.col_start, df_loc.col_len);
-            cmdarg_err_cont("    %s\n    %s\n", rfilter, err_msg_cont);
-            g_free(err_msg);
-            g_free(err_msg_cont);
+        if (!compile_dfilter(rfilter, &rfcode)) {
             epan_cleanup();
             extcap_cleanup();
 
@@ -2044,12 +2072,7 @@ main(int argc, char *argv[])
 
     if (dfilter != NULL) {
         ws_debug("Compiling display filter: '%s'", dfilter);
-        if (!dfilter_compile2(dfilter, &dfcode, &err_msg, &df_loc)) {
-            cmdarg_err("%s", err_msg);
-            err_msg_cont = ws_strdup_error_offset(NULL, df_loc.col_start, df_loc.col_len);
-            cmdarg_err_cont("    %s\n    %s\n", dfilter, err_msg_cont);
-            g_free(err_msg);
-            g_free(err_msg_cont);
+        if (!compile_dfilter(dfilter, &dfcode)) {
             epan_cleanup();
             extcap_cleanup();