Re: [RFA/DWARF] Set enum type "flag_enum" and "unsigned" flags at type creation.

[Joel Brobecker <brobecker@adacore.com>]

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> I'll add a comment in the code...

Attached is the patch adding the comment...

gdb/ChangeLog:

        * dwarf2read.c (read_subrange_type): Add comment.

Thanks,
-- 
Joel

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From dbb9c2b1f231262ece36790241fe1fc3902cf03d Mon Sep 17 00:00:00 2001
From: Joel Brobecker <brobecker@adacore.com>
Date: Wed, 26 Feb 2014 10:53:05 -0800
Subject: [PATCH] Add comment in dwarf2read.c::read_subrange_type

This comment explains why we sometimes sign-extend the range type
bounds when we normally shouldn't have to.

gdb/ChangeLog:

        * dwarf2read.c (read_subrange_type): Add comment.
---
 gdb/ChangeLog    | 4 ++++
 gdb/dwarf2read.c | 7 +++++++
 2 files changed, 11 insertions(+)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 8f2f0dc..49d8113 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,9 @@
 2014-02-27  Joel Brobecker  <brobecker@adacore.com>
 
+	* dwarf2read.c (read_subrange_type): Add comment.
+
+2014-02-27  Joel Brobecker  <brobecker@adacore.com>
+
 	* dwarf2read.c (update_enumeration_type_from_children): New
 	function, mostly extracted from process_structure_scope.
 	(read_enumeration_type): Call update_enumeration_type_from_children.
diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
index 00bba47..52208d6 100644
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -14522,6 +14522,13 @@ read_subrange_type (struct die_info *die, struct dwarf2_cu *cu)
 	}
     }
 
+  /* Normally, the DWARF producers are expected to use a signed
+     constant form (Eg. DW_FORM_sdata) to express negative bounds.
+     But this is unfortunately not always the case, as witnessed
+     with GCC, for instance, where the ambiguous DW_FORM_dataN form
+     is used instead.  To work around that ambiguity, we treat
+     the bounds as signed, and thus sign-extend their values, when
+     the base type is signed.  */
   negative_mask =
     (LONGEST) -1 << (TYPE_LENGTH (base_type) * TARGET_CHAR_BIT - 1);
   if (!TYPE_UNSIGNED (base_type) && (low & negative_mask))
-- 
1.8.3.2