> so accessing the With_Flags array (which is not empty) yields a SEGV
> because the base pointer is equal to Last_Unit (i.e. 2). In other words,
> the GIMPLE code looks legitimate and the bug is very likely in the stack
> slot allocation code (maybe triggered by the newly created zero-sized
> arrays).
And this is the real fix. Richard, do you want me to apply (part of it)?
* cfgexpand.c (add_stack_var): Assert that the alignment is not zero.
* tree-ssa-ccp.c (fold_builtin_alloca_for_var): Force BITS_PER_UNIT
alignment at least on the new variable.
--
Eric Botcazou
Index: cfgexpand.c
===================================================================
--- cfgexpand.c (revision 178422)
+++ cfgexpand.c (working copy)
@@ -271,6 +271,8 @@ add_stack_var (tree decl)
if (v->size == 0)
v->size = 1;
v->alignb = align_local_variable (SSAVAR (decl));
+ /* An alignment of zero can mightily confuse us later. */
+ gcc_assert (v->alignb != 0);
/* All variables are initially in their own partition. */
v->representative = stack_vars_num;
Index: tree-ssa-ccp.c
===================================================================
--- tree-ssa-ccp.c (revision 178422)
+++ tree-ssa-ccp.c (working copy)
@@ -1722,6 +1722,8 @@ fold_builtin_alloca_for_var (gimple stmt
elem_type = build_nonstandard_integer_type (BITS_PER_UNIT, 1);
n_elem = size * 8 / BITS_PER_UNIT;
align = MIN (size * 8, BIGGEST_ALIGNMENT);
+ if (align < BITS_PER_UNIT)
+ align = BITS_PER_UNIT;
array_type = build_array_type_nelts (elem_type, n_elem);
var = create_tmp_var (array_type, NULL);
DECL_ALIGN (var) = align;
