Message ID | 20240215151947.38390-1-polacek@redhat.com |
---|---|
State | New |
Headers | show |
Series | c++: implicit move with throw [PR113853] | expand |
On 2/15/24 10:19, Marek Polacek wrote: > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? > > -- >8 -- > Here we have > > template<class T> > auto is_throwable(T t) -> decltype(throw t, true) { ... } > > where we didn't properly mark 't' as IMPLICIT_RVALUE_P, which caused > the wrong overload to have been chosen. Jason figured out it's because > we don't correctly implement [expr.prim.id.unqual]#4.2, which post-P2266 > says that an id-expression is move-eligible if > > "the id-expression (possibly parenthesized) is the operand of > a throw-expression, and names an implicitly movable entity that belongs > to a scope that does not contain the compound-statement of the innermost > lambda-expression, try-block, or function-try-block (if any) whose > compound-statement or ctor-initializer contains the throw-expression." > > I worked out that it's trying to say that given > > struct X { > X(); > X(const X&); > X(X&&) = delete; > }; > > the following should fail: the scope of the throw is an sk_try, and it's > also x's scope S, and S "does not contain the compound-statement of the > *try-block" so x is move-eligible, so we move, so we fail. > > void f () > try { > X x; > throw x; // use of deleted function > } catch (...) { > } > > Whereas here: > > void g (X x) > try { > throw x; > } catch (...) { > } > > the throw is again in an sk_try, but x's scope is an sk_function_parms > which *does* contain the {} of the *try-block, so x is not move-eligible, > so we don't move, so we use X(const X&), and the code is fine. > > The current code also doesn't seem to handle > > void h (X x) { > void z (decltype(throw x, true)); > } > > where there's no enclosing lambda or sk_try so we should move. > > I'm not doing anything about lambdas because we shouldn't reach the > code at the end of the function: the DECL_HAS_VALUE_EXPR_P check > shouldn't let us go further. > > PR c++/113789 > PR c++/113853 > > gcc/cp/ChangeLog: > > * typeck.cc (treat_lvalue_as_rvalue_p): Update code to better > reflect [expr.prim.id.unqual]#4.2. > > gcc/testsuite/ChangeLog: > > * g++.dg/cpp0x/sfinae69.C: Remove dg-bogus. > * g++.dg/cpp0x/sfinae70.C: New test. > * g++.dg/cpp0x/sfinae71.C: New test. > * g++.dg/cpp0x/sfinae72.C: New test. > * g++.dg/cpp2a/implicit-move4.C: New test. > --- > gcc/cp/typeck.cc | 32 +++++------ > gcc/testsuite/g++.dg/cpp0x/sfinae69.C | 2 +- > gcc/testsuite/g++.dg/cpp0x/sfinae70.C | 16 ++++++ > gcc/testsuite/g++.dg/cpp0x/sfinae71.C | 17 ++++++ > gcc/testsuite/g++.dg/cpp0x/sfinae72.C | 17 ++++++ > gcc/testsuite/g++.dg/cpp2a/implicit-move4.C | 59 +++++++++++++++++++++ > 6 files changed, 126 insertions(+), 17 deletions(-) > create mode 100644 gcc/testsuite/g++.dg/cpp0x/sfinae70.C > create mode 100644 gcc/testsuite/g++.dg/cpp0x/sfinae71.C > create mode 100644 gcc/testsuite/g++.dg/cpp0x/sfinae72.C > create mode 100644 gcc/testsuite/g++.dg/cpp2a/implicit-move4.C > > diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc > index 132c55cfc6d..0dc44cd87ca 100644 > --- a/gcc/cp/typeck.cc > +++ b/gcc/cp/typeck.cc > @@ -10837,37 +10837,37 @@ treat_lvalue_as_rvalue_p (tree expr, bool return_p) > parenthesized) id-expression that names an implicitly movable entity > declared in the body or parameter-declaration-clause of the innermost > enclosing function or lambda-expression, */ > - if (DECL_CONTEXT (retval) != current_function_decl) > - return NULL_TREE; > if (return_p) > { > + if (DECL_CONTEXT (retval) != current_function_decl) > + return NULL_TREE; > expr = move (expr); > if (expr == error_mark_node) > return NULL_TREE; > return set_implicit_rvalue_p (expr); > } > > - /* if the operand of a throw-expression is a (possibly parenthesized) > - id-expression that names an implicitly movable entity whose scope does not > - extend beyond the compound-statement of the innermost try-block or > - function-try-block (if any) whose compound-statement or ctor-initializer > - encloses the throw-expression, */ > + /* if the id-expression (possibly parenthesized) is the operand of > + a throw-expression, and names an implicitly movable entity that belongs > + to a scope that does not contain the compound-statement of the innermost > + lambda-expression, try-block, or function-try-block (if any) whose > + compound-statement or ctor-initializer contains the throw-expression. */ Please also mention here why you aren't checking for lambdas. > /* C++20 added move on throw of parms. */ > if (TREE_CODE (retval) == PARM_DECL && cxx_dialect < cxx20) > return NULL_TREE; > > for (cp_binding_level *b = current_binding_level; > - ; b = b->level_chain) > - { > - for (tree decl = b->names; decl; decl = TREE_CHAIN (decl)) > - if (decl == retval) > - return set_implicit_rvalue_p (move (expr)); > - if (b->kind == sk_function_parms > - || b->kind == sk_try > - || b->kind == sk_namespace) > + b->kind != sk_namespace; b = b->level_chain) > + if (b->kind == sk_try) > + { > + for (tree decl = b->names; decl; decl = TREE_CHAIN (decl)) > + if (decl == retval) > + return set_implicit_rvalue_p (move (expr)); > return NULL_TREE; > - } What if the variable is in a block nested within the try-block? I think we still want to walk b->names for every inner binding level. Jason
diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc index 132c55cfc6d..0dc44cd87ca 100644 --- a/gcc/cp/typeck.cc +++ b/gcc/cp/typeck.cc @@ -10837,37 +10837,37 @@ treat_lvalue_as_rvalue_p (tree expr, bool return_p) parenthesized) id-expression that names an implicitly movable entity declared in the body or parameter-declaration-clause of the innermost enclosing function or lambda-expression, */ - if (DECL_CONTEXT (retval) != current_function_decl) - return NULL_TREE; if (return_p) { + if (DECL_CONTEXT (retval) != current_function_decl) + return NULL_TREE; expr = move (expr); if (expr == error_mark_node) return NULL_TREE; return set_implicit_rvalue_p (expr); } - /* if the operand of a throw-expression is a (possibly parenthesized) - id-expression that names an implicitly movable entity whose scope does not - extend beyond the compound-statement of the innermost try-block or - function-try-block (if any) whose compound-statement or ctor-initializer - encloses the throw-expression, */ + /* if the id-expression (possibly parenthesized) is the operand of + a throw-expression, and names an implicitly movable entity that belongs + to a scope that does not contain the compound-statement of the innermost + lambda-expression, try-block, or function-try-block (if any) whose + compound-statement or ctor-initializer contains the throw-expression. */ /* C++20 added move on throw of parms. */ if (TREE_CODE (retval) == PARM_DECL && cxx_dialect < cxx20) return NULL_TREE; for (cp_binding_level *b = current_binding_level; - ; b = b->level_chain) - { - for (tree decl = b->names; decl; decl = TREE_CHAIN (decl)) - if (decl == retval) - return set_implicit_rvalue_p (move (expr)); - if (b->kind == sk_function_parms - || b->kind == sk_try - || b->kind == sk_namespace) + b->kind != sk_namespace; b = b->level_chain) + if (b->kind == sk_try) + { + for (tree decl = b->names; decl; decl = TREE_CHAIN (decl)) + if (decl == retval) + return set_implicit_rvalue_p (move (expr)); return NULL_TREE; - } + } + + return set_implicit_rvalue_p (move (expr)); } /* Warn about dubious usage of std::move (in a return statement, if RETURN_P diff --git a/gcc/testsuite/g++.dg/cpp0x/sfinae69.C b/gcc/testsuite/g++.dg/cpp0x/sfinae69.C index 361e0b79ba2..60eba61165d 100644 --- a/gcc/testsuite/g++.dg/cpp0x/sfinae69.C +++ b/gcc/testsuite/g++.dg/cpp0x/sfinae69.C @@ -15,7 +15,7 @@ constexpr bool is_throwable(...) { return false; } constexpr bool b = is_throwable<moveonly>(moveonly{}); #if __cplusplus >= 202002L -static_assert (b, "move from the function parameter"); // { dg-bogus "" "PR113853" { xfail c++20 } } +static_assert (b, "move from the function parameter"); #else static_assert (!b, "no move from the function parameter"); #endif diff --git a/gcc/testsuite/g++.dg/cpp0x/sfinae70.C b/gcc/testsuite/g++.dg/cpp0x/sfinae70.C new file mode 100644 index 00000000000..48ea70a61a4 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp0x/sfinae70.C @@ -0,0 +1,16 @@ +// PR c++/113789 +// { dg-do compile { target c++11 } } + +struct AutoPtr { + AutoPtr() = default; + AutoPtr(AutoPtr&) {} +}; + +template<class T> auto f(T p, int) -> decltype(throw p, 1) = delete; +template<class T> void f(T p, long); + +void +g () +{ + f (AutoPtr (), 42); // { dg-error "use of deleted function" "" { target c++20_down } } +} diff --git a/gcc/testsuite/g++.dg/cpp0x/sfinae71.C b/gcc/testsuite/g++.dg/cpp0x/sfinae71.C new file mode 100644 index 00000000000..2fefe5f70e0 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp0x/sfinae71.C @@ -0,0 +1,17 @@ +// PR c++/113789 +// { dg-do compile { target c++11 } } +// Like sfinae70.C but T&&. + +struct AutoPtr { + AutoPtr() = default; + AutoPtr(AutoPtr&) {} +}; + +template<class T> auto f(T&& p, int) -> decltype(throw p, 1) = delete; +template<class T> void f(T p, long); + +void +g () +{ + f (AutoPtr (), 42); // { dg-error "use of deleted function" "" { target c++20_down } } +} diff --git a/gcc/testsuite/g++.dg/cpp0x/sfinae72.C b/gcc/testsuite/g++.dg/cpp0x/sfinae72.C new file mode 100644 index 00000000000..397cdbd8c23 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp0x/sfinae72.C @@ -0,0 +1,17 @@ +// PR c++/113789 +// { dg-do compile { target c++11 } } +// Like sfinae70.C but (). + +struct AutoPtr { + AutoPtr() = default; + AutoPtr(AutoPtr&) {} +}; + +template<class T> auto f(T p, int) -> decltype(throw (p), 1) = delete; +template<class T> void f(T p, long); + +void +g () +{ + f (AutoPtr (), 42); // { dg-error "use of deleted function" "" { target c++20_down } } +} diff --git a/gcc/testsuite/g++.dg/cpp2a/implicit-move4.C b/gcc/testsuite/g++.dg/cpp2a/implicit-move4.C new file mode 100644 index 00000000000..af4f62e5c7f --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/implicit-move4.C @@ -0,0 +1,59 @@ +// PR c++/113853 +// { dg-do compile { target c++20 } } + +struct X { + X(); + X(const X&); + X(X&&) = delete; +}; + +void +f1 () +{ + try { + ; + } catch (X x) { + throw x; // { dg-error "use of deleted function" } + } +} + +void +f2 (X x) +try { + ; +} catch (...) { + throw x; // { dg-error "use of deleted function" } +} + +void +f3 () +try { + X x; + throw x; // { dg-error "use of deleted function" } +} catch (...) { +} + +void +f4 (X x) +try { + throw x; +} catch (...) { +} + +void +f5 (X x) +{ + void g (decltype(throw x, true)); // { dg-error "use of deleted function|expected" } +} + +// The "expected" shouldn't be here, c++/113924. +void +f6 (X x, int = decltype(throw x, true){}) // { dg-error "use of deleted function|expected" } +{ +} + +void +f7 (X x) +{ + [&] { throw x; }; +}