From 8f9dd1b0bdd935592ba151e9d843fddf6193afbc Mon Sep 17 00:00:00 2001 From: Marek Polacek Date: Wed, 19 Feb 2020 16:36:38 -0500 Subject: [PATCH] c++: Fix wrong-code with non-constexpr constructor [PR93169] In order to detect modifying constant objects in constexpr evaluation, which is UB, in r10-2655 I added code that sets TREE_READONLY on CONSTRUCTORs of const-qualified objects after they have been fully constructed. But I never made sure that what we're setting the flag on actually is a CONSTRUCTOR. Consequently, as this test case shows, we could set TREE_READONLY on a VAR_DECL that in fact wasn't constant, causing problems later. Fixed by setting the flag on CONSTRUCTORs only, and only when the evaluation produced something constant. 2020-02-19 Marek Polacek PR c++/93169 - wrong-code with a non-constexpr constructor. * constexpr.c (cxx_eval_call_expression): Only set TREE_READONLY on constant CONSTRUCTORs. * g++.dg/cpp0x/constexpr-93169.C: New test. --- gcc/cp/ChangeLog | 6 ++++++ gcc/cp/constexpr.c | 3 ++- gcc/testsuite/ChangeLog | 5 +++++ gcc/testsuite/g++.dg/cpp0x/constexpr-93169.C | 21 ++++++++++++++++++++ 4 files changed, 34 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/g++.dg/cpp0x/constexpr-93169.C diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog index f6b5517d5e4..e1ac5b0f29e 100644 --- a/gcc/cp/ChangeLog +++ b/gcc/cp/ChangeLog @@ -1,3 +1,9 @@ +2020-02-19 Marek Polacek + + PR c++/93169 - wrong-code with a non-constexpr constructor. + * constexpr.c (cxx_eval_call_expression): Only set TREE_READONLY + on constant CONSTRUCTORs. + 2020-02-15 Marek Polacek PR c++/93710 - poor diagnostic for array initializer. diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c index bf7a2643003..128f760778b 100644 --- a/gcc/cp/constexpr.c +++ b/gcc/cp/constexpr.c @@ -2474,7 +2474,8 @@ cxx_eval_call_expression (const constexpr_ctx *ctx, tree t, /*lval*/false, non_constant_p, overflow_p); - TREE_READONLY (e) = true; + if (TREE_CODE (e) == CONSTRUCTOR && !*non_constant_p) + TREE_READONLY (e) = true; } /* Forget the saved values of the callee's SAVE_EXPRs and diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index 049c343fe43..a54505ed73e 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,8 @@ +2020-02-19 Marek Polacek + + PR c++/93169 - wrong-code with a non-constexpr constructor. + * g++.dg/cpp0x/constexpr-93169.C: New test. + 2020-02-19 Martin Sebor PR tree-optimization/92128 diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-93169.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-93169.C new file mode 100644 index 00000000000..79fd352c0c5 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-93169.C @@ -0,0 +1,21 @@ +// PR c++/93169 - Wrong-code with a non-constexpr constructor. +// { dg-do run { target c++11 } } +// { dg-options "-O2" } + +template class B { + struct C { + T h; + constexpr C() {} + ~C() {} + } c; +}; +struct S { + int g; + S() { g = 2; } +}; + +int +main() +{ + static const B f; +} -- 2.30.2