https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69368
--- Comment #13 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Seems get_ref_base_and_extent already has code for some cases of the flexible
array members, but it has apparently some dead code in it that wasn't really
meant to be dead (hint, this check is after a while (1) { switch (TREE_CODE
(exp)) { ... } exp = TREE_OPERAND (exp, 0); } loop, thus break inside of the
switch does not terminate the loop and the only way to get out of the loop is
then goto done;, but that bypasses the stmt):
--- gcc/tree-dfa.c.jj 2016-01-21 08:58:44.000000000 +0100
+++ gcc/tree-dfa.c 2016-02-04 11:18:40.061621702 +0100
@@ -588,6 +588,7 @@ get_ref_base_and_extent (tree exp, HOST_
exp = TREE_OPERAND (exp, 0);
}
+ done:
/* We need to deal with variable arrays ending structures. */
if (seen_variable_array_ref
&& maxsize != -1
@@ -597,7 +598,6 @@ get_ref_base_and_extent (tree exp, HOST_
== wi::to_offset (TYPE_SIZE (TREE_TYPE (exp))))))
maxsize = -1;
- done:
if (!wi::fits_shwi_p (bitsize) || wi::neg_p (bitsize))
{
*poffset = 0;
But I guess even this doesn't help, while it will help poor man's flexible
array members in C/C++, in this Fortran case the problem is that there is
COMMON /FMCOM/ X(1)
in this TU, while
COMMON /FMCOM / X(1000000)
in some other TU, and get_ref_base_and_extent caps maxsize at DECL_SIZE -
bit_offset (which is generally right, but Fortran COMMON is just weird).
So, perhaps we want some flag on the Fortran COMMON decls that would be set on
COMMON that ends with an array and would tell get_ref_base_and_extent (and
other spots?) that accesses can be beyond end of the decl?
