Clean up ftype-conversion and dfilter error message string handling.

Have dfilter_compile() take an additional gchar ** argument, pointing to
a gchar * item that, on error, gets set to point to a g_malloc()ed error
string.  That removes one bit of global state from the display filter
parser, and doesn't impose a fixed limit on the error message strings.

Have fvalue_from_string() and fvalue_from_unparsed() take a gchar **
argument, pointer to a gchar * item, rather than an error-reporting
function, and set the gchar * item to point to a g_malloc()ed error
string on an error.

Allow either gchar ** argument to be null; if the argument is null, no
error message is allocated or provided.

Change-Id: Ibd36b8aaa9bf4234aa6efa1e7fb95f7037493b4c
Reviewed-on: https://code.wireshark.org/review/6608
Reviewed-by: Guy Harris <guy@alum.mit.edu>

2 files changed, 8 insertions, 5 deletions

diff --git a/epan/wslua/wslua_field.c b/epan/wslua/wslua_field.c
index 5fe0715bba..5e96f25c83 100644
--- a/epan/wslua/wslua_field.c
+++ b/epan/wslua/wslua_field.c
@@ -475,6 +475,7 @@ void lua_prime_all_fields(proto_tree* tree _U_) {
     GString* fake_tap_filter = g_string_new("frame");
     guint i;
     static gboolean fake_tap = FALSE;
+    gchar *err_msg;
 
     for(i=0; i < wanted_fields->len; i++) {
         Field f = (Field)g_ptr_array_index(wanted_fields,i);
@@ -514,8 +515,9 @@ void lua_prime_all_fields(proto_tree* tree _U_) {
                 dfilter_free(wslua_dfilter);
                 wslua_dfilter = NULL;
             }
-            if (!dfilter_compile(fake_tap_filter->str, &wslua_dfilter)) {
-                report_failure("while compiling dfilter for wslua: '%s'", fake_tap_filter->str);
+            if (!dfilter_compile(fake_tap_filter->str, &wslua_dfilter, &err_msg)) {
+                report_failure("while compiling dfilter \"%s\" for wslua: %s", fake_tap_filter->str, err_msg);
+                g_free(err_msg);
             }
         }
     }
diff --git a/epan/wslua/wslua_gui.c b/epan/wslua/wslua_gui.c
index b73564eff9..34623dfd71 100644
--- a/epan/wslua/wslua_gui.c
+++ b/epan/wslua/wslua_gui.c
@@ -730,7 +730,7 @@ WSLUA_FUNCTION wslua_open_capture_file(lua_State* L) { /* Open and display a cap
 
     const char* fname = luaL_checkstring(L,WSLUA_ARG_open_capture_file_FILENAME);
     const char* filter = luaL_optstring(L,WSLUA_ARG_open_capture_file_FILTER,NULL);
-    const char* error = NULL;
+    char* error = NULL;
 
     if (!ops->open_file) {
         WSLUA_ERROR(open_capture_file, "GUI not available");
@@ -740,9 +740,10 @@ WSLUA_FUNCTION wslua_open_capture_file(lua_State* L) { /* Open and display a cap
     if (! ops->open_file(fname,filter,&error) ) {
         lua_pushboolean(L,FALSE);
 
-        if (error)
+        if (error) {
             lua_pushstring(L,error);
-        else
+            g_free(error);
+        } else
             lua_pushnil(L);
 
         return 2;