Re: [PATCH] c++: fix ICE with constexpr ARRAY_REF [PR110382]
On 7/21/23 18:38, Marek Polacek wrote: Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/13? -- >8 -- This code in cxx_eval_array_reference has been hard to get right. In r12-2304 I added some code; in r13-5693 I removed some of it. Here the problematic line is "S s = arr[0];" which causes a crash on the assert in verify_ctor_sanity: gcc_assert (!ctx->object || !DECL_P (ctx->object) || ctx->global->get_value (ctx->object) == ctx->ctor); ctx->object is the VAR_DECL 's', which is correct here. The second line points to the problem: we replaced ctx->ctor in cxx_eval_array_reference: new_ctx.ctor = build_constructor (elem_type, NULL); // #1 ...and this code doesn't also clear(/set) new_ctx.object like everywhere else in constexpr.cc that sets new_ctx.ctor. Fixing that should make the testcase work. which I think we shouldn't have; the CONSTRUCTOR we created in cxx_eval_constant_expression/DECL_EXPR new_ctx.ctor = build_constructor (TREE_TYPE (r), NULL); had the right type. Indeed, and using it rather than building a new one seems like a valid optimization for trunk. I also notice that the DECL_EXPR code calls unshare_constructor, which should be unnecessary if init == ctx->ctor? We still need #1 though. E.g., in constexpr-96241.C, we never set ctx.ctor/object before calling cxx_eval_array_reference, so we have to build a CONSTRUCTOR there. And in constexpr-101371-2.C we have a ctx.ctor, but it has the wrong type, so we need a new one. PR c++/110382 gcc/cp/ChangeLog: * constexpr.cc (cxx_eval_array_reference): Create a new constructor only when we don't already have a matching one. gcc/testsuite/ChangeLog: * g++.dg/cpp1y/constexpr-110382.C: New test. --- gcc/cp/constexpr.cc | 5 - gcc/testsuite/g++.dg/cpp1y/constexpr-110382.C | 17 + 2 files changed, 21 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/g++.dg/cpp1y/constexpr-110382.C diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc index fb94f3cefcb..518b7c7a2d5 100644 --- a/gcc/cp/constexpr.cc +++ b/gcc/cp/constexpr.cc @@ -4291,7 +4291,10 @@ cxx_eval_array_reference (const constexpr_ctx *ctx, tree t, else val = build_value_init (elem_type, tf_warning_or_error); - if (!SCALAR_TYPE_P (elem_type)) + if (!SCALAR_TYPE_P (elem_type) + /* Create a new constructor only if we don't already have one that +is suitable. */ + && !(ctx->ctor && same_type_p (elem_type, TREE_TYPE (ctx->ctor We generally use same_type_ignoring_top_level_qualifiers_p in the constexpr code. Jason
[PATCH] c++: fix ICE with constexpr ARRAY_REF [PR110382]
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/13? -- >8 -- This code in cxx_eval_array_reference has been hard to get right. In r12-2304 I added some code; in r13-5693 I removed some of it. Here the problematic line is "S s = arr[0];" which causes a crash on the assert in verify_ctor_sanity: gcc_assert (!ctx->object || !DECL_P (ctx->object) || ctx->global->get_value (ctx->object) == ctx->ctor); ctx->object is the VAR_DECL 's', which is correct here. The second line points to the problem: we replaced ctx->ctor in cxx_eval_array_reference: new_ctx.ctor = build_constructor (elem_type, NULL); // #1 which I think we shouldn't have; the CONSTRUCTOR we created in cxx_eval_constant_expression/DECL_EXPR new_ctx.ctor = build_constructor (TREE_TYPE (r), NULL); had the right type. We still need #1 though. E.g., in constexpr-96241.C, we never set ctx.ctor/object before calling cxx_eval_array_reference, so we have to build a CONSTRUCTOR there. And in constexpr-101371-2.C we have a ctx.ctor, but it has the wrong type, so we need a new one. PR c++/110382 gcc/cp/ChangeLog: * constexpr.cc (cxx_eval_array_reference): Create a new constructor only when we don't already have a matching one. gcc/testsuite/ChangeLog: * g++.dg/cpp1y/constexpr-110382.C: New test. --- gcc/cp/constexpr.cc | 5 - gcc/testsuite/g++.dg/cpp1y/constexpr-110382.C | 17 + 2 files changed, 21 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/g++.dg/cpp1y/constexpr-110382.C diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc index fb94f3cefcb..518b7c7a2d5 100644 --- a/gcc/cp/constexpr.cc +++ b/gcc/cp/constexpr.cc @@ -4291,7 +4291,10 @@ cxx_eval_array_reference (const constexpr_ctx *ctx, tree t, else val = build_value_init (elem_type, tf_warning_or_error); - if (!SCALAR_TYPE_P (elem_type)) + if (!SCALAR_TYPE_P (elem_type) + /* Create a new constructor only if we don't already have one that +is suitable. */ + && !(ctx->ctor && same_type_p (elem_type, TREE_TYPE (ctx->ctor { new_ctx = *ctx; new_ctx.ctor = build_constructor (elem_type, NULL); diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-110382.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-110382.C new file mode 100644 index 000..317c5ecfcd5 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-110382.C @@ -0,0 +1,17 @@ +// PR c++/110382 +// { dg-do compile { target c++14 } } + +struct S { + double a = 0; +}; + +constexpr double +g () +{ + S arr[1]; + S s = arr[0]; + (void) arr[0]; + return s.a; +} + +int main() { return g (); } base-commit: 87516efcbe28884c39a8c68e600d11cc91ed96c7 -- 2.41.0