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 (file)
--- 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 (file)
--- 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);