procyberian/gcc
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

c++: don't do constexpr folding in unevaluated context

Browse source 
The implicit constexpr patch revealed that we were doing constant evaluation
of arbitrary expressions in unevaluated contexts, leading to failure when we
tried to evaluate e.g. a call to declval.  This is wrong more generally;
only manifestly-constant-evaluated expressions should be evaluated within
an unevaluated operand.

Making this change revealed a case we were failing to mark as manifestly
constant-evaluated.

gcc/cp/ChangeLog:

	* constexpr.c (maybe_constant_value): Don't evaluate
	in an unevaluated operand unless manifestly const-evaluated.
	(fold_non_dependent_expr_template): Likewise.
	* decl.c (compute_array_index_type_loc): This context is
	manifestly constant-evaluated.
This commit is contained in:
Jason Merrill 2021-11-05 00:08:53 -04:00
parent 267318a285
commit 4df7f8c798
2 changed files with 8 additions and 1 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

7
gcc/cp/constexpr.c
View file

@ -7696,6 +7696,10 @@ maybe_constant_value (tree t, tree decl, bool manifestly_const_eval)
return r;
}
/* Don't evaluate an unevaluated operand. */
if (cp_unevaluated_operand)
return t;
uid_sensitive_constexpr_evaluation_checker c;
r = cxx_eval_outermost_constant_expr (t, true, true, false, false, decl);
gcc_checking_assert (r == t
@ -7759,6 +7763,9 @@ fold_non_dependent_expr_template (tree t, tsubst_flags_t complain,
return t;
}
if (cp_unevaluated_operand && !manifestly_const_eval)
return t;
tree r = cxx_eval_outermost_constant_expr (t, true, true,
manifestly_const_eval,
false, object);

2
gcc/cp/decl.c
View file

@ -11000,7 +11000,7 @@ compute_array_index_type_loc (location_t name_loc, tree name, tree size,
cp_convert (ssizetype, integer_one_node,
complain),
complain);
itype = maybe_constant_value (itype);
itype = maybe_constant_value (itype, NULL_TREE, true);
}
if (!TREE_CONSTANT (itype))