On Thu, 12 Sept 2024 at 16:02, Jason Merrill wrote:
>
> On 9/12/24 4:49 AM, Jonathan Wakely wrote:
> > Tested x86_64-linux. OK for trunk?
> >
> > -- >8 --
> >
> > The standard says that std::launder is ill-formed for function pointers
> > and cv void pointers, so there's no reason for __builtin_launder to
> > accept them. This change allows implementations of std::launder to defer
> > to the built-in for error checking, although libstdc++ will continue to
> > diagnose it directly for more user-friendly diagnostics.
> >
> > PR c++/116673
> >
> > gcc/cp/ChangeLog:
> >
> > * semantics.cc (finish_builtin_launder): Diagnose function
> > pointers and cv void pointers.
> >
> > gcc/testsuite/ChangeLog:
> >
> > * g++.dg/cpp1z/launder10.C: New test.
> > ---
> > gcc/cp/semantics.cc | 17 +++++++++++++----
> > gcc/testsuite/g++.dg/cpp1z/launder10.C | 15 +++++++++++++++
> > 2 files changed, 28 insertions(+), 4 deletions(-)
> > create mode 100644 gcc/testsuite/g++.dg/cpp1z/launder10.C
> >
> > diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
> > index 63212afafb3..b194b01f865 100644
> > --- a/gcc/cp/semantics.cc
> > +++ b/gcc/cp/semantics.cc
> > @@ -13482,11 +13482,20 @@ finish_builtin_launder (location_t loc, tree arg,
> > tsubst_flags_t complain)
> > arg = decay_conversion (arg, complain);
> > if (error_operand_p (arg))
> > return error_mark_node;
> > - if (!type_dependent_expression_p (arg)
> > - && !TYPE_PTR_P (TREE_TYPE (arg)))
> > + if (!type_dependent_expression_p (arg))
> > {
> > - error_at (loc, "non-pointer argument to %<__builtin_launder%>");
> > - return error_mark_node;
> > + tree type = TREE_TYPE (arg);
> > + if (!TYPE_PTR_P (type))
> > + {
> > + error_at (loc, "non-pointer argument to %<__builtin_launder%>");
> > + return error_mark_node;
> > + }
> > + else if (!object_type_p (TREE_TYPE (type)))
> > + {
> > + // std::launder is ill-formed for function and cv void pointers.
> > + error_at (loc, "invalid argument to %<__builtin_launder%>");
>
> Let's be more specific by combining both errors into
>
> "type %qT of argument to %<__builtin_launder"> is not a pointer to
> object type"
>
> The tests can also be combined to !TYPE_PTROB_P.
>
> OK with that change.
Thanks, here's what I pushed.
commit 9fe57e4879de93b6e3c7b4c226f42d5f3a48474f
Author: Jonathan Wakely <jwak...@redhat.com>
Date: Wed Sep 11 11:47:44 2024
c++: Make __builtin_launder reject invalid types [PR116673]
The standard says that std::launder is ill-formed for function pointers
and cv void pointers, so there's no reason for __builtin_launder to
accept them. This change allows implementations of std::launder to defer
to the built-in for error checking, although libstdc++ will continue to
diagnose it directly for more user-friendly diagnostics.
PR c++/116673
gcc/cp/ChangeLog:
* semantics.cc (finish_builtin_launder): Diagnose function
pointers and cv void pointers.
gcc/testsuite/ChangeLog:
* g++.dg/cpp1z/launder2.C: Adjust dg-error strings.
* g++.dg/cpp1z/launder10.C: New test.
diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 63212afafb3..8219d6410b8 100644
--- a/gcc/cp/semantics.cc
+++ b/gcc/cp/semantics.cc
@@ -13482,10 +13482,10 @@ finish_builtin_launder (location_t loc, tree arg,
tsubst_flags_t complain)
arg = decay_conversion (arg, complain);
if (error_operand_p (arg))
return error_mark_node;
- if (!type_dependent_expression_p (arg)
- && !TYPE_PTR_P (TREE_TYPE (arg)))
+ if (!type_dependent_expression_p (arg) && !TYPE_PTROB_P (TREE_TYPE (arg)))
{
- error_at (loc, "non-pointer argument to %<__builtin_launder%>");
+ error_at (loc, "type %qT of argument to %<__builtin_launder%> "
+ "is not a pointer to object type", TREE_TYPE (arg));
return error_mark_node;
}
if (processing_template_decl)
diff --git a/gcc/testsuite/g++.dg/cpp1z/launder10.C
b/gcc/testsuite/g++.dg/cpp1z/launder10.C
new file mode 100644
index 00000000000..2109a2e3839
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/launder10.C
@@ -0,0 +1,15 @@
+// PR c++/116673
+// { dg-do compile }
+
+void
+bar (void *p)
+{
+ __builtin_launder (bar); // { dg-error {argument to '__builtin_launder'} }
+ __builtin_launder (p); // { dg-error {argument to '__builtin_launder'} }
+ const void* cp = p;
+ __builtin_launder (cp); // { dg-error {argument to '__builtin_launder'} }
+ volatile void* vp = p;
+ __builtin_launder (vp); // { dg-error {argument to '__builtin_launder'} }
+ const volatile void* cvp = p;
+ __builtin_launder (cvp); // { dg-error {argument to '__builtin_launder'} }
+}
diff --git a/gcc/testsuite/g++.dg/cpp1z/launder2.C
b/gcc/testsuite/g++.dg/cpp1z/launder2.C
index 9cd1779704b..a2d44861265 100644
--- a/gcc/testsuite/g++.dg/cpp1z/launder2.C
+++ b/gcc/testsuite/g++.dg/cpp1z/launder2.C
@@ -4,11 +4,11 @@ int a;
int *b = __builtin_launder (); // { dg-error "wrong number of
arguments to" }
int *c = __builtin_launder (&a, 2); // { dg-error "wrong number of
arguments to" }
int *d = __builtin_launder (&a);
-int e = __builtin_launder (a); // { dg-error "non-pointer argument to"
}
+int e = __builtin_launder (a); // { dg-error "not a pointer to object
type" }
int &f = a;
-int g = __builtin_launder (f); // { dg-error "non-pointer argument to"
}
+int g = __builtin_launder (f); // { dg-error "not a pointer to object
type" }
-template <typename T> T f1 (T x) { return __builtin_launder (x); } // {
dg-error "non-pointer argument to" }
+template <typename T> T f1 (T x) { return __builtin_launder (x); } // {
dg-error "not a pointer to object type" }
template <typename T> T f2 (T x) { return __builtin_launder (x); }
int h = f1 (a);
