On Tue, 15 Feb 2022, Patrick Palka wrote: > Here we're crashing from potential_constant_expression because it tries > to perform trial evaluation of the first operand '(bool)__r' of the > conjunction (which is overall wrapped in a NON_DEPENDENT_EXPR), but > cxx_eval_constant_expression ICEs on unhandled trees (of which CAST_EXPR > is one). > > Since cxx_eval_constant_expression always treats NON_DEPENDENT_EXPR > as non-constant, and since NON_DEPENDENT_EXPR is also opaque to > instantiate_non_dependent_expr, it seems futile to have p_c_e_1 ever > return true for NON_DEPENDENT_EXPR, so let's just instead return false > and avoid recursing. > > Alternatively p_c_e_1 could continue to recurse into NON_DEPENDENT_EXPR, > but with trial evaluation disabled by setting processing_template_decl, > but as mentioned it seems pointless for p_c_e_1 to ever return true for > NON_DEPENDENT_EXPR. > > Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for > trunk and perhaps 10/11? > > PR c++/104507 > > gcc/cp/ChangeLog: > > * constexpr.cc (potential_constant_expression_1) > <case NON_DEPENDENT_EXPR>: Return false rather than recursing. > > gcc/testsuite/ChangeLog: > > * g++.dg/template/non-dependent21.C: New test. > --- > gcc/cp/constexpr.cc | 4 +++- > gcc/testsuite/g++.dg/template/non-dependent21.C | 9 +++++++++ > 2 files changed, 12 insertions(+), 1 deletion(-) > create mode 100644 gcc/testsuite/g++.dg/template/non-dependent21.C > > diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc > index 7274c3b760e..c0523551f7b 100644 > --- a/gcc/cp/constexpr.cc > +++ b/gcc/cp/constexpr.cc > @@ -9065,6 +9065,9 @@ potential_constant_expression_1 (tree t, bool > want_rval, bool strict, bool now, > case BIND_EXPR: > return RECUR (BIND_EXPR_BODY (t), want_rval); > > + case NON_DEPENDENT_EXPR: > + return false;
Since we're not issuing a diagnostic in this case, I suppose we should also assert that tf_error isn't set. Bootstrapped and regtested on x86_64-pc-linux-gnu. -- >8 -- PR c++/104507 gcc/cp/ChangeLog: * constexpr.cc (potential_constant_expression_1) <case NON_DEPENDENT_EXPR>: Return false instead of recursing. Assert tf_error isn't set. gcc/testsuite/ChangeLog: * g++.dg/template/non-dependent21.C: New test. --- gcc/cp/constexpr.cc | 5 ++++- gcc/testsuite/g++.dg/template/non-dependent21.C | 9 +++++++++ 2 files changed, 13 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/g++.dg/template/non-dependent21.C diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc index 7274c3b760e..b363ef08411 100644 --- a/gcc/cp/constexpr.cc +++ b/gcc/cp/constexpr.cc @@ -9065,6 +9065,10 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, case BIND_EXPR: return RECUR (BIND_EXPR_BODY (t), want_rval); + case NON_DEPENDENT_EXPR: + gcc_checking_assert (!(flags & tf_error)); + return false; + case CLEANUP_POINT_EXPR: case MUST_NOT_THROW_EXPR: case TRY_CATCH_EXPR: @@ -9072,7 +9076,6 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now, case EH_SPEC_BLOCK: case EXPR_STMT: case PAREN_EXPR: - case NON_DEPENDENT_EXPR: /* For convenience. */ case LOOP_EXPR: case EXIT_EXPR: diff --git a/gcc/testsuite/g++.dg/template/non-dependent21.C b/gcc/testsuite/g++.dg/template/non-dependent21.C new file mode 100644 index 00000000000..89900837b8b --- /dev/null +++ b/gcc/testsuite/g++.dg/template/non-dependent21.C @@ -0,0 +1,9 @@ +// PR c++/104507 + +extern const char *_k_errmsg[]; + +template<class> +const char* DoFoo(int __r, int __s) { + const char* n = _k_errmsg[(bool)__r && __s ? 1 : 2]; + return n; +} -- 2.35.1.129.gb80121027d