From 3a2257e6b3fa288d6c50831987949b9ff7dfb865 Mon Sep 17 00:00:00 2001 From: Marek Polacek Date: Sat, 4 Dec 2021 12:07:41 -0500 Subject: [PATCH] c++: Fix for decltype and bit-fields [PR95009] Here, decltype deduces the wrong type for certain expressions involving bit-fields. Unlike in C, in C++ bit-field width is explicitly not part of the type, so I think decltype should never deduce to 'int:N'. The problem isn't that we're not calling unlowered_expr_type--we are--it's that is_bitfield_expr_with_lowered_type only handles certain codes, but not others. For example, += works fine but ++ does not. This also fixes decltype-bitfield2.C where we were crashing (!), but unfortunately it does not fix 84516 or 70733 where the problem is likely a missing call to unlowered_expr_type. It occurs to me now that typeof likely has had the same issue, but this patch should fix that too. PR c++/95009 gcc/cp/ChangeLog: * typeck.c (is_bitfield_expr_with_lowered_type) : Handle UNARY_PLUS_EXPR, NEGATE_EXPR, NON_LVALUE_EXPR, BIT_NOT_EXPR, P*CREMENT_EXPR too. gcc/testsuite/ChangeLog: * g++.dg/cpp0x/decltype-bitfield1.C: New test. * g++.dg/cpp0x/decltype-bitfield2.C: New test. --- gcc/cp/typeck.c | 14 ++++-- gcc/testsuite/g++.dg/cpp0x/decltype-bitfield1.C | 65 +++++++++++++++++++++++++ gcc/testsuite/g++.dg/cpp0x/decltype-bitfield2.C | 18 +++++++ 3 files changed, 94 insertions(+), 3 deletions(-) create mode 100644 gcc/testsuite/g++.dg/cpp0x/decltype-bitfield1.C create mode 100644 gcc/testsuite/g++.dg/cpp0x/decltype-bitfield2.C diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c index 5ed9a5a..4e60db4 100644 --- a/gcc/cp/typeck.c +++ b/gcc/cp/typeck.c @@ -2209,9 +2209,9 @@ invalid_nonstatic_memfn_p (location_t loc, tree expr, tsubst_flags_t complain) return false; } -/* If EXP is a reference to a bitfield, and the type of EXP does not - match the declared type of the bitfield, return the declared type - of the bitfield. Otherwise, return NULL_TREE. */ +/* If EXP is a reference to a bit-field, and the type of EXP does not + match the declared type of the bit-field, return the declared type + of the bit-field. Otherwise, return NULL_TREE. */ tree is_bitfield_expr_with_lowered_type (const_tree exp) @@ -2230,6 +2230,14 @@ is_bitfield_expr_with_lowered_type (const_tree exp) case MODIFY_EXPR: case SAVE_EXPR: + case UNARY_PLUS_EXPR: + case PREDECREMENT_EXPR: + case PREINCREMENT_EXPR: + case POSTDECREMENT_EXPR: + case POSTINCREMENT_EXPR: + case NEGATE_EXPR: + case NON_LVALUE_EXPR: + case BIT_NOT_EXPR: return is_bitfield_expr_with_lowered_type (TREE_OPERAND (exp, 0)); case COMPONENT_REF: diff --git a/gcc/testsuite/g++.dg/cpp0x/decltype-bitfield1.C b/gcc/testsuite/g++.dg/cpp0x/decltype-bitfield1.C new file mode 100644 index 0000000..2d8d8e8 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp0x/decltype-bitfield1.C @@ -0,0 +1,65 @@ +// PR c++/95009 +// { dg-do compile { target c++11 } } + +struct false_type { static constexpr bool value = false; }; +struct true_type { static constexpr bool value = true; }; +template +struct is_same : false_type {}; +template +struct is_same : true_type {}; + +struct A { + int i : 31; + unsigned long l : 37; +} a; + +void +g () +{ + // Careful: pre{in,de}crements are lvalues -> deduce T&. */ + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); + static_assert (is_same::value, ""); +} diff --git a/gcc/testsuite/g++.dg/cpp0x/decltype-bitfield2.C b/gcc/testsuite/g++.dg/cpp0x/decltype-bitfield2.C new file mode 100644 index 0000000..4bf9c76 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp0x/decltype-bitfield2.C @@ -0,0 +1,18 @@ +// PR c++/95009 +// { dg-do compile { target c++11 } } + +struct A { + int i:31; +}; + +template +void f () +{ +} + +int main () +{ + A a; + f(); + f(); +} -- 2.7.4