https://gcc.gnu.org/PR95508 https://bugs.gentoo.org/729434 From 1bab254fd30c2b94a675b9057349fc80946375b1 Mon Sep 17 00:00:00 2001 From: Marek Polacek Date: Wed, 17 Jun 2020 14:38:05 -0400 Subject: [PATCH] c++: ICE with IMPLICIT_CONV_EXPR in array subscript [PR95508] Since r10-7096 convert_like, when called in a template, creates an IMPLICIT_CONV_EXPR when we're converting to/from array type. In this test, we have e[f], and we're converting f (of type class A) to int, so convert_like in build_new_op_1 created the IMPLICIT_CONV_EXPR that got into cp_build_array_ref which calls maybe_constant_value. My patch above failed to adjust this spot to call fold_non_dependent_expr instead, which can handle codes like I_C_E in a template. Fixed by using a new function maybe_fold_non_dependent_expr, which, if the expr can't be evaluated to a constant, returns the original expression. gcc/cp/ChangeLog: PR c++/95508 * constexpr.c (maybe_fold_non_dependent_expr): New. * cp-tree.h (maybe_fold_non_dependent_expr): Declare. * typeck.c (cp_build_array_ref): Call maybe_fold_non_dependent_expr instead of maybe_constant_value. gcc/testsuite/ChangeLog: PR c++/95508 * g++.dg/template/conv16.C: New test. --- gcc/cp/constexpr.c | 13 +++++++++++++ gcc/cp/cp-tree.h | 2 ++ gcc/cp/typeck.c | 2 +- gcc/testsuite/g++.dg/template/conv16.C | 17 +++++++++++++++++ 4 files changed, 33 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/g++.dg/template/conv16.C diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c index 75c4a1f6197..bda8d6a8bef 100644 --- a/gcc/cp/constexpr.c +++ b/gcc/cp/constexpr.c @@ -7043,6 +7043,19 @@ fold_non_dependent_expr (tree t, return maybe_constant_value (t, object, manifestly_const_eval); } +/* Like fold_non_dependent_expr, but if EXPR couldn't be folded to a constant, + return the original expression. */ + +tree +maybe_fold_non_dependent_expr (tree expr, + tsubst_flags_t complain/*=tf_warning_or_error*/) +{ + tree t = fold_non_dependent_expr (expr, complain); + if (t && TREE_CONSTANT (t)) + return t; + + return expr; +} /* Like maybe_constant_init but first fully instantiate the argument. */ diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h index eab9c29af0a..f220ed9f52a 100644 --- a/gcc/cp/cp-tree.h +++ b/gcc/cp/cp-tree.h @@ -7955,6 +7955,8 @@ extern tree maybe_constant_init (tree, tree = NULL_TREE, bool = false); extern tree fold_non_dependent_expr (tree, tsubst_flags_t = tf_warning_or_error, bool = false, tree = NULL_TREE); +extern tree maybe_fold_non_dependent_expr (tree, + tsubst_flags_t = tf_warning_or_error); extern tree fold_non_dependent_init (tree, tsubst_flags_t = tf_warning_or_error, bool = false); diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c index 2fd6dbee468..5f8f8290f0f 100644 --- a/gcc/cp/typeck.c +++ b/gcc/cp/typeck.c @@ -3553,7 +3553,7 @@ cp_build_array_ref (location_t loc, tree array, tree idx, pointer arithmetic.) */ idx = cp_perform_integral_promotions (idx, complain); - idx = maybe_constant_value (idx); + idx = maybe_fold_non_dependent_expr (idx, complain); /* An array that is indexed by a non-constant cannot be stored in a register; we must be able to do diff --git a/gcc/testsuite/g++.dg/template/conv16.C b/gcc/testsuite/g++.dg/template/conv16.C new file mode 100644 index 00000000000..c0843efdf9d --- /dev/null +++ b/gcc/testsuite/g++.dg/template/conv16.C @@ -0,0 +1,17 @@ +// PR c++/95508 +// { dg-do compile } + +template +struct A; +template +struct B { + operator int () { return 0; } +}; +template <> +struct A : B {}; +struct D { + template + int foo () { return e[f]; } + int e[6]; + A f; +}; -- 2.27.0