Message ID | 20200219221249.101318-1-polacek@redhat.com |
---|---|
State | New |
Headers | show |
Series | c++: Fix wrong-code with non-constexpr constructor [PR93169] | expand |
On 2/19/20 11:12 PM, Marek Polacek wrote: > 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. > > Bootstrapped/regtested on x86_64-linux, ok for trunk? OK. > 2020-02-19 Marek Polacek <polacek@redhat.com> > > PR c++/93169 - wrong-code with a non-constexpr constructor. > * constexpr.c (cxx_eval_call_expression): Only set TREE_READONLY > on constant CONSTRUCTORs.
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/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 <typename T> class B { + struct C { + T h; + constexpr C() {} + ~C() {} + } c; +}; +struct S { + int g; + S() { g = 2; } +}; + +int +main() +{ + static const B<S> f; +}