From: Andrew Burgess <andrew.burgess@embecosm.com>
Date: Fri, 2 Mar 2018 15:48:23 +0000 (+0000)
Subject: gdb/amd64: Ignore zero sized fields when calling functions
X-Git-Tag: binutils-2_31~1127
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=5dc4391345f6e86906a57af1434025cfb47b4100;p=platform%2Fupstream%2Fbinutils.git

gdb/amd64: Ignore zero sized fields when calling functions

In some cases passing an argument to a function on amd64, or attempting
to fetch the return value, can trigger an assertion failure within GDB.
An example of a type that would trigger such an error is:

  struct foo_t
  {
    long double a;
    struct {
      struct {
        /* Empty.  */
      } es1;
    } s1;
  };

GCC does permit empty structures, so we should probably support this.

The test that exposes this bug is in the next commit along with the
RiscV support.

gdb/ChangeLog:

	* amd64-tdep.c (amd64_classify_aggregate): Ignore zero sized
	fields within aggregates.
---

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 4a44af4..28e5e89 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,8 @@
+2018-03-06  Andrew Burgess  <andrew.burgess@embecosm.com>
+
+	* amd64-tdep.c (amd64_classify_aggregate): Ignore zero sized
+	fields within aggregates.
+
 2018-03-04  Simon Marchi  <simon.marchi@polymtl.ca>
 
 	* record-btrace.c (btrace_print_lines): Change type of flags to
diff --git a/gdb/amd64-tdep.c b/gdb/amd64-tdep.c
index 6b92c92..07eef5e 100644
--- a/gdb/amd64-tdep.c
+++ b/gdb/amd64-tdep.c
@@ -601,8 +601,9 @@ amd64_classify_aggregate (struct type *type, enum amd64_reg_class theclass[2])
 	    bitsize = TYPE_LENGTH (subtype) * 8;
 	  endpos = (TYPE_FIELD_BITPOS (type, i) + bitsize - 1) / 64;
 
-	  /* Ignore static fields.  */
-	  if (field_is_static (&TYPE_FIELD (type, i)))
+	  /* Ignore static fields, or empty fields, for example nested
+	     empty structures.*/
+	  if (field_is_static (&TYPE_FIELD (type, i)) || bitsize == 0)
 	    continue;
 
 	  gdb_assert (pos == 0 || pos == 1);