On Thu, Feb 15, 2024 at 04:36:40PM -0500, Jason Merrill wrote:
> 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.
Done.
> > /* 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.
Oy, that's a bug. Fixed by moving the == sk_try check below.
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 | 24 +++---
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 | 88 +++++++++++++++++++++
6 files changed, 152 insertions(+), 12 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..f5a0a2273be 100644
--- a/gcc/cp/typeck.cc
+++ b/gcc/cp/typeck.cc
@@ -10837,37 +10837,39 @@ 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;
+ /* We don't check for lambda-expression here, because we should not get past
+ the DECL_HAS_VALUE_EXPR_P check above. */
for (cp_binding_level *b = current_binding_level;
- ; b = b->level_chain)
+ b->kind != sk_namespace; 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)
+ if (b->kind == sk_try)
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..09ac5c93ab9
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/implicit-move4.C
@@ -0,0 +1,88 @@
+// 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
+f2b (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
+f3b ()
+try {
+ {
+ X x;
+ throw x; // { dg-error "use of deleted function" }
+ }
+} catch (...) {
+}
+
+void
+f4 (X x)
+try {
+ throw x;
+} catch (...) {
+}
+
+void
+f4b (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; };
+}
base-commit: 7c6071a66f32f43cea7aa4aa32d89b338e768307
--
2.43.2
