From 2dcdd15d0bafb9b45a8d7ff580217bd6ac1f0975 Mon Sep 17 00:00:00 2001 From: Jakub Jelinek Date: Thu, 11 Feb 2021 17:24:17 +0100 Subject: [PATCH] c++: Fix zero initialization of flexible array members [PR99033] array_type_nelts returns error_mark_node for type of flexible array members and build_zero_init_1 was placing an error_mark_node into the CONSTRUCTOR, on which e.g. varasm ICEs. I think there is nothing erroneous on zero initialization of flexible array members though, such arrays should simply get no elements, like they do if such classes are constructed (everything except when some larger initializer comes from an explicit initializer). So, this patch handles [] arrays in zero initialization like [0] arrays and fixes handling of the [0] arrays - the tree_int_cst_equal (max_index, integer_minus_one_node) check didn't do what it thought it would do, max_index is typically unsigned integer (sizetype) and so it is never equal to a -1. What the patch doesn't do and maybe would be desirable is if it returns error_mark_node for other reasons let the recursive callers not stick that into CONSTRUCTOR but return error_mark_node instead. But I don't have a testcase where that would be needed right now. 2021-02-11 Jakub Jelinek PR c++/99033 * init.c (build_zero_init_1): Handle zero initialiation of flexible array members like initialization of [0] arrays. Use integer_minus_onep instead of comparison to integer_minus_one_node and integer_zerop instead of comparison against size_zero_node. Formatting fixes. * g++.dg/ext/flexary38.C: New test. --- gcc/cp/init.c | 20 +++++++++++--------- gcc/testsuite/g++.dg/ext/flexary38.C | 18 ++++++++++++++++++ 2 files changed, 29 insertions(+), 9 deletions(-) create mode 100644 gcc/testsuite/g++.dg/ext/flexary38.C diff --git a/gcc/cp/init.c b/gcc/cp/init.c index 131da1a4ae4..1381a23449e 100644 --- a/gcc/cp/init.c +++ b/gcc/cp/init.c @@ -247,9 +247,12 @@ build_zero_init_1 (tree type, tree nelts, bool static_storage_p, /* Iterate over the array elements, building initializations. */ if (nelts) - max_index = fold_build2_loc (input_location, - MINUS_EXPR, TREE_TYPE (nelts), - nelts, integer_one_node); + max_index = fold_build2_loc (input_location, MINUS_EXPR, + TREE_TYPE (nelts), nelts, + build_one_cst (TREE_TYPE (nelts))); + /* Treat flexible array members like [0] arrays. */ + else if (TYPE_DOMAIN (type) == NULL_TREE) + max_index = build_minus_one_cst (sizetype); else max_index = array_type_nelts (type); @@ -261,20 +264,19 @@ build_zero_init_1 (tree type, tree nelts, bool static_storage_p, /* A zero-sized array, which is accepted as an extension, will have an upper bound of -1. */ - if (!tree_int_cst_equal (max_index, integer_minus_one_node)) + if (!integer_minus_onep (max_index)) { constructor_elt ce; /* If this is a one element array, we just use a regular init. */ - if (tree_int_cst_equal (size_zero_node, max_index)) + if (integer_zerop (max_index)) ce.index = size_zero_node; else ce.index = build2 (RANGE_EXPR, sizetype, size_zero_node, - max_index); + max_index); - ce.value = build_zero_init_1 (TREE_TYPE (type), - /*nelts=*/NULL_TREE, - static_storage_p, NULL_TREE); + ce.value = build_zero_init_1 (TREE_TYPE (type), /*nelts=*/NULL_TREE, + static_storage_p, NULL_TREE); if (ce.value) { vec_alloc (v, 1); diff --git a/gcc/testsuite/g++.dg/ext/flexary38.C b/gcc/testsuite/g++.dg/ext/flexary38.C new file mode 100644 index 00000000000..4fa987bcb41 --- /dev/null +++ b/gcc/testsuite/g++.dg/ext/flexary38.C @@ -0,0 +1,18 @@ +// PR c++/99033 +// { dg-do compile } +// { dg-options "" } + +struct T { int t; }; +struct S { char c; int T::*b[]; } a; +struct U { char c; int T::*b[0]; } b; +struct V { char c; int T::*b[1]; } c; +struct W { char c; int T::*b[2]; } d; + +void +foo () +{ + a.c = 1; + b.c = 2; + c.c = 3; + d.c = 4; +} -- 2.30.2