From: Eric Botcazou <ebotcazou@adacore.com>
Date: Tue, 19 Nov 2024 18:14:53 +0000 (+0100)
Subject: ada: Fix internal error on packed record with 0-size component
X-Git-Tag: basepoints/gcc-16~3346
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=a72d2abbfc10e4d9620b17ffc41bdbcb98bff100;p=thirdparty%2Fgcc.git

ada: Fix internal error on packed record with 0-size component

The problem is that the order of components listed in a constant CONSTRUCTOR
does not match that of the associated record type.

gcc/ada/ChangeLog:

	* gcc-interface/utils2.cc (compare_elmt_bitpos): Deal specially with
	0-sized components when the bit position is the same.
---

diff --git a/gcc/ada/gcc-interface/utils2.cc b/gcc/ada/gcc-interface/utils2.cc
index 8eebf5935960..e91f67d7e452 100644
--- a/gcc/ada/gcc-interface/utils2.cc
+++ b/gcc/ada/gcc-interface/utils2.cc
@@ -2113,7 +2113,23 @@ compare_elmt_bitpos (const void *rt1, const void *rt2)
   const int ret
     = tree_int_cst_compare (bit_position (field1), bit_position (field2));
 
-  return ret ? ret : (int) (DECL_UID (field1) - DECL_UID (field2));
+  if (ret)
+    return ret;
+
+  /* The bit position can be the same if one of the fields has zero size.
+     In this case, if the other has nonzero size, put the former first to
+     match the layout done by components_to_record.  Otherwise, preserve
+     the order of the source code.  */
+
+  const bool field1_zero_size = integer_zerop (DECL_SIZE (field1));
+  const bool field2_zero_size = integer_zerop (DECL_SIZE (field2));
+
+  if (field1_zero_size && !field2_zero_size)
+    return -1;
+  else if (!field1_zero_size && field2_zero_size)
+    return 1;
+  else
+    return (int) (DECL_UID (field1) - DECL_UID (field2));
 }
 
 /* Return a CONSTRUCTOR of TYPE whose elements are V.  */