[gcc r15-3614] c++: Make __builtin_launder reject invalid types [PR116673]

[Jonathan Wakely]

https://gcc.gnu.org/g:9fe57e4879de93b6e3c7b4c226f42d5f3a48474f

commit r15-3614-g9fe57e4879de93b6e3c7b4c226f42d5f3a48474f
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Wed Sep 11 11:47:44 2024 +0100

    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:
---
 gcc/cp/semantics.cc                    |  6 +++---
 gcc/testsuite/g++.dg/cpp1z/launder10.C | 15 +++++++++++++++
 gcc/testsuite/g++.dg/cpp1z/launder2.C  |  6 +++---
 3 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
index 63212afafb3b..8219d6410b8e 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 000000000000..2109a2e38393
--- /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 9cd1779704b3..a2d448612655 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);