diagnostics: show locations in full when debugging

This is meant for developers, not end users, that's why I attached it
to --trace.

* src/getargs.h, src/getargs.c (trace_locations): New.
* src/location.c (location_print): Use it.

src/getargs.c

@@ -185,6 +185,7 @@ ARGMATCH_VERIFY (report_args, report_types);
 static const char * const trace_args[] =
 {
   "none       - no traces",
+  "locations  - full display of the locations",
   "scan       - grammar scanner traces",
   "parse      - grammar parser traces",
   "automaton  - construction of the automaton",
@@ -206,6 +207,7 @@ static const char * const trace_args[] =
 static const int trace_types[] =
 {
   trace_none,
+  trace_locations,
   trace_scan,
   trace_parse,
   trace_automaton,

src/getargs.h

@@ -104,6 +104,7 @@ enum trace
     trace_muscles   = 1 << 11, /**< M4 definitions of the muscles. */
     trace_ielr      = 1 << 12, /**< IELR conversion. */
     trace_closure   = 1 << 13, /**< Input/output of closure(). */
+    trace_locations = 1 << 14, /**< Full display of locations. */
     trace_all       = ~0       /**< All of the above.  */
   };
 /** What debug items bison displays during its run.  */

src/location.c

@@ -27,6 +27,7 @@
 #include <sys/stat.h> /* fstat */
 
 #include "complain.h"
+#include "getargs.h"
 #include "location.h"
 
 location const empty_location = EMPTY_LOCATION_INIT;
@@ -96,11 +97,26 @@ location_compute (location *loc, boundary *cur, char const *token, size_t size)
     complain (loc, Wother, _("byte number overflow"));
 }
 
+static unsigned
+boundary_print (boundary const *b, FILE *out)
+{
+  return fprintf (out, "%s:%d.%d@%d",
+                  quotearg_n_style (3, escape_quoting_style, b->file),
+                  b->line, b->column, b->byte);
+}
 
 unsigned
 location_print (location loc, FILE *out)
 {
   unsigned res = 0;
+  if (trace_flag & trace_locations)
+    {
+      res += boundary_print (&loc.start, out);
+      res += fprintf (out, "-");
+      res += boundary_print (&loc.end, out);
+    }
+  else
+    {
       int end_col = 0 != loc.end.column ? loc.end.column - 1 : 0;
       res += fprintf (out, "%s",
                       quotearg_n_style (3, escape_quoting_style, loc.start.file));
@@ -133,6 +149,7 @@ location_print (location loc, FILE *out)
           else if (0 <= end_col && loc.start.column < end_col)
             res += fprintf (out, "-%d", end_col);
         }
+    }
 
   return res;
 }