Hi!
The C and C++ FEs handle zero sized arrays differently, C uses
NULL TYPE_MAX_VALUE on non-NULL TYPE_DOMAIN on complete ARRAY_TYPEs
with bitsize_zero_node TYPE_SIZE, while C++ FE likes to set
TYPE_MAX_VALUE to the largest value (and min to the lowest).
Martin has used array_type_nelts in get_parm_array_spec where the
function on the C form of [0] arrays returns error_mark_node and the code
crashes soon afterwards. The following patch teaches array_type_nelts about
this (e.g. dwarf2out already handles that as [0]). While it will change
what is_empty_type returns for certain types (e.g. struct S { int a[0]; };),
as those types occupy zero bits in C, it should make an ABI difference.
So, the tree.c change makes the c-decl.c code handle the [0] arrays
like any other constant extents, and the c-decl.c change just makes sure
that if we'd run into error_mark_node e.g. from the VLA expressions, we
don't crash on those.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2020-11-18 Jakub Jelinek <ja...@redhat.com>
PR c/97860
* tree.c (array_type_nelts): For complete arrays with zero min
and NULL max and zero size return -1.
* c-decl.c (get_parm_array_spec): Bail out of nelts is
error_operand_p.
* gcc.dg/pr97860.c: New test.
--- gcc/tree.c.jj 2020-11-18 09:40:09.798660999 +0100
+++ gcc/tree.c 2020-11-18 20:02:41.655398514 +0100
@@ -3483,7 +3483,17 @@ array_type_nelts (const_tree type)
/* TYPE_MAX_VALUE may not be set if the array has unknown length. */
if (!max)
- return error_mark_node;
+ {
+ /* zero sized arrays are represented from C FE as complete types with
+ NULL TYPE_MAX_VALUE and zero TYPE_SIZE, while C++ FE represents
+ them as min 0, max -1. */
+ if (COMPLETE_TYPE_P (type)
+ && integer_zerop (TYPE_SIZE (type))
+ && integer_zerop (min))
+ return build_int_cst (TREE_TYPE (min), -1);
+
+ return error_mark_node;
+ }
return (integer_zerop (min)
? max
--- gcc/c/c-decl.c.jj 2020-11-11 01:46:03.245697697 +0100
+++ gcc/c/c-decl.c 2020-11-18 20:03:53.053602265 +0100
@@ -5775,6 +5775,8 @@ get_parm_array_spec (const struct c_parm
type = TREE_TYPE (type))
{
tree nelts = array_type_nelts (type);
+ if (error_operand_p (nelts))
+ return attrs;
if (TREE_CODE (nelts) != INTEGER_CST)
{
/* Each variable VLA bound is represented by the dollar
--- gcc/testsuite/gcc.dg/pr97860.c.jj 2020-11-18 15:15:08.858931877 +0100
+++ gcc/testsuite/gcc.dg/pr97860.c 2020-11-18 15:14:50.751135430 +0100
@@ -0,0 +1,11 @@
+/* PR c/97860 */
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+void
+foo (int n)
+{
+ typedef int T[0];
+ typedef T V[n];
+ void bar (V);
+}
Jakub
