On September 3, 2016 5:23:35 PM GMT+02:00, Tom de Vries
<tom_devr...@mentor.com> wrote:
>Hi,
>
>this patch fixes a c++ ICE, a p1 6/7 regression.
>
>
>Consider test.C:
>...
>void bar (__builtin_va_list &);
>
>struct c
>{
> operator const __builtin_va_list &();
> operator __builtin_va_list &();
>};
>
>void
>foo (void) {
> struct c c1;
>
> bar (c1);
>}
>...
>
>The compiler ICEs as follows:
>...
>test.C: In function ‘void foo()’:
>test.C:13:10: internal compiler error: canonical types differ for
>identical types __va_list_tag [1] and __va_list_tag [1]
> bar (c1);
> ^
>comptypes(tree_node*, tree_node*, int)
> src/gcc/cp/typeck.c:1430
>reference_related_p(tree_node*, tree_node*)
> src/gcc/cp/call.c:1415
>reference_binding
> src/gcc/cp/call.c:1559
>implicit_conversion
> src/gcc/cp/call.c:1805
>build_user_type_conversion_1
> src/gcc/cp/call.c:3776
>reference_binding
> src/gcc/cp/call.c:1664
>implicit_conversion
> src/gcc/cp/call.c:1805
>add_function_candidate
> src/gcc/cp/call.c:2141
>add_candidates
> src/gcc/cp/call.c:5394
>perform_overload_resolution
> src/gcc/cp/call.c:4066
>build_new_function_call(tree_node*, vec<tree_node*, va_gc, vl_embed>**,
> bool, int)
> src/gcc/cp/call.c:4143
>finish_call_expr(tree_node*, vec<tree_node*, va_gc, vl_embed>**, bool,
> bool, int)
> src/gcc/cp/semantics.c:2440
>...
>
>The regression is caused by the commit for PR70955, that adds a
>"sysv_abi va_list" attribute to the struct in the va_list type (which
>is
>an array of one of struct).
>
>The ICE in comptypes happens as follows: we're comparing two versions
>of
>va_list type (with identical array element type), each with the
>canonical type set to themselves. Since the types are considered
>identical, they're supposed to have identical canonical types, which is
Did you figure out why they are not assigned the same canonical type?
Richard.
>not the case, and we run into the ICE.
>
>The patch fixes the ICE by setting the canonical type of the va_list
>struct and array to NULL, forcing structural comparison.
>
>
>This fix causes a regression for test2.C:
>...
>template <typename T>
>int
>fn7 (T ap)
>{
> return __builtin_va_arg(ap, int);
>}
>
>int
>fn8 (__builtin_va_list ap)
>{
> return fn7<__builtin_va_list> (ap);
>}
>...
>
>It causes this warning to appear:
>...
>test2.C: In function ‘int fn8(__va_list_tag*)’:
>test2.C:11:36: warning: ignoring attributes applied to ‘__va_list_tag’
>after definition [-Wattributes]
> return fn7<__builtin_va_list> (ap);
>...
>
>The patch removes the warning by considering the attribute on the
>va_list struct type as engrained in apply_identity_attributes.
>
>
>Bootstrapped and reg-tested on x86_64.
>
>OK for trunk, 6 branch?
>
>Thanks,
>- Tom
