gdb: fix pretty printing max depth behaviour

The 'print max-depth' feature incorrectly causes GDB to skip printing
the string representation of pretty printed variables if the variable
is stored at a nested depth corresponding to the set max-depth value.
This change ensures that it is always printed before checking whether
the maximum print depth has been reached.

Regression tested with GCC 7.3.0 on x86_64, ppc64le, aarch64.

gdb/ChangeLog:

	* cp-valprint.c (cp_print_value): Replaced duplicate code.
	* guile/scm-pretty-print.c (ppscm_print_children): Check max_depth
	just before printing child values.
	(gdbscm_apply_val_pretty_printer): Don't check max_depth before
	printing string representation.
	* python/py-prettyprint.c (print_children): Check max_depth just
	before printing child values.
	(gdbpy_apply_val_pretty_printer): Don't check max_depth before
	printing string representation.

gdb/testsuite/ChangeLog:

	* gdb.python/py-format-string.c: Added a variable to test.
	* gdb.python/py-format-string.exp: Check string representation is
	printed at appropriate max_depth settings.
	* gdb.python/py-nested-maps.exp: Likewise.
	* gdb.guile/scm-pretty-print.exp: Add additional tests.

1 files changed, 16 insertions, 14 deletions

diff --git a/gdb/guile/scm-pretty-print.c b/gdb/guile/scm-pretty-print.c
index 605615e..2dd7798 100644
--- a/gdb/guile/scm-pretty-print.c
+++ b/gdb/guile/scm-pretty-print.c
@@ -818,21 +818,29 @@ ppscm_print_children (SCM printer, enum display_hint hint,
       gdb::unique_xmalloc_ptr<char> name
 	= gdbscm_scm_to_c_string (scm_name);
 
-      /* Print initial "{".  For other elements, there are three cases:
+      /* Print initial "=" to separate print_string_repr output and
+	 children.  For other elements, there are three cases:
 	 1. Maps.  Print a "," after each value element.
 	 2. Arrays.  Always print a ",".
 	 3. Other.  Always print a ",".  */
       if (i == 0)
-	{
-	 if (printed_nothing)
-	   fputs_filtered ("{", stream);
-	 else
-	   fputs_filtered (" = {", stream);
-       }
-
+      {
+	if (!printed_nothing)
+	  fputs_filtered (" = ", stream);
+      }
       else if (! is_map || i % 2 == 0)
 	fputs_filtered (pretty ? "," : ", ", stream);
 
+      /* Skip printing children if max_depth has been reached.  This check
+	 is performed after print_string_repr and the "=" separator so that
+	 these steps are not skipped if the variable is located within the
+	 permitted depth.  */
+      if (val_print_check_max_depth (stream, recurse, options, language))
+	goto done;
+      else if (i == 0)
+	/* Print initial "{" to bookend children.  */
+	fputs_filtered ("{", stream);
+
       /* In summary mode, we just want to print "= {...}" if there is
 	 a value.  */
       if (options->summary)
@@ -991,12 +999,6 @@ gdbscm_apply_val_pretty_printer (const struct extension_language_defn *extlang,
     }
   gdb_assert (ppscm_is_pretty_printer_worker (printer));
 
-  if (val_print_check_max_depth (stream, recurse, options, language))
-    {
-      result = EXT_LANG_RC_OK;
-      goto done;
-    }
-
   /* If we are printing a map, we want some special formatting.  */
   hint = ppscm_get_display_hint_enum (printer);
   if (hint == HINT_ERROR)