dfilter: Add location tracking to scanner and use it to report errors

Add location tracking as a column offset and length from offset
to the scanner. Our input is a single line only so we don't need
to track line offset.

Record that information in the syntax tree. Return the error location
in dfilter_compile(). Use it in dftest to mark the location of the
error in the filter string. Later it would be nice to use the location
in the GUI as well.

$ dftest "ip.proto == aaaaaa and tcp.port == 123"
Filter: ip.proto == aaaaaa and tcp.port == 123
dftest: "aaaaaa" cannot be found among the possible values for ip.proto.
	ip.proto == aaaaaa and tcp.port == 123
	            ^~~~~~

1 files changed, 13 insertions, 3 deletions

diff --git a/epan/dfilter/dfilter-int.h b/epan/dfilter/dfilter-int.h
index 346f6f6804..dc50f6a75a 100644
--- a/epan/dfilter/dfilter-int.h
+++ b/epan/dfilter/dfilter-int.h
@@ -44,6 +44,8 @@ typedef struct {
 	GPtrArray	*deprecated;
 	GHashTable	*references; /* hfinfo -> pointer to GSList of fvalues */
 	GHashTable	*loaded_references;
+	char		*expanded_text;
+	stloc_t		err_loc;
 } dfwork_t;
 
 /*
@@ -53,6 +55,8 @@ typedef struct {
 	dfwork_t *dfw;
 	GString* quoted_string;
 	gboolean raw_string;
+	stloc_t string_loc;
+	stloc_t location;
 } df_scanner_state_t;
 
 /* Constructor/Destructor prototypes for Lemon Parser */
@@ -66,14 +70,20 @@ void Dfilter(void*, int, stnode_t*, dfwork_t*);
 #define SCAN_FAILED	-1	/* not 0, as that means end-of-input */
 
 void
-dfilter_vfail(dfwork_t *dfw, const char *format, va_list args);
+dfilter_vfail(dfwork_t *dfw, stloc_t *err_loc,
+			const char *format, va_list args);
 
 void
-dfilter_fail(dfwork_t *dfw, const char *format, ...) G_GNUC_PRINTF(2, 3);
+dfilter_fail(dfwork_t *dfw, stloc_t *err_loc,
+			const char *format, ...) G_GNUC_PRINTF(3, 4);
 
 WS_NORETURN
 void
-dfilter_fail_throw(dfwork_t *dfw, long code, const char *format, ...) G_GNUC_PRINTF(3, 4);
+dfilter_fail_throw(dfwork_t *dfw, stloc_t *err_loc,
+			long code, const char *format, ...) G_GNUC_PRINTF(4, 5);
+
+void
+dfw_set_error_location(dfwork_t *dfw, stloc_t *err_loc);
 
 void
 add_deprecated_token(dfwork_t *dfw, const char *token);