From: Marek Polacek <polacek@redhat.com>
Date: Thu, 7 May 2026 22:09:57 +0000 (-0400)
Subject: c++: fix ICE with invalid targ [PR125043]
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=90ec6eeca09f5a411fd7878e2532a7ac2f2e3d71;p=thirdparty%2Fgcc.git

c++: fix ICE with invalid targ [PR125043]

The patch that allowed DECL_NTTP_OBJECT_P in invalid_tparm_referent_p
also added the assert checking for tinfos/__func__ (r14-8189).  But in
these tests we got to the assert with a temporary object coming from
create_temporary_var: either a reference temporary or compound literal
temporary.  The former could be checked by seeing if the name starts
with _ZGR but the latter don't have it.  So perhaps we can just check
DECL_IGNORED_P, always set for create_temporary_var objects.

	PR c++/115181
	PR c++/125043
	PR c++/124979

gcc/cp/ChangeLog:

	* pt.cc (invalid_tparm_referent_p): Allow DECL_IGNORED_P in an
	assert.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp1z/nontype-auto27.C: New test.
	* g++.dg/cpp1z/nontype-auto28.C: New test.
	* g++.dg/cpp2a/nontype-class75.C: New test.

Reviewed-by: Jason Merrill <jason@redhat.com>
---

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 6992b5196fe..b6e8948f005 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -7439,18 +7439,22 @@ invalid_tparm_referent_p (tree type, tree expr, tsubst_flags_t complain)
 			"because %qD has no linkage", expr, type, decl);
 	    return true;
 	  }
-	/* C++17: For a non-type template-parameter of reference or pointer
-	   type, the value of the constant expression shall not refer to (or
-	   for a pointer type, shall not be the address of):
-	   * a subobject (4.5),
-	   * a temporary object (15.2),
-	   * a string literal (5.13.5),
-	   * the result of a typeid expression (8.2.8), or
-	   * a predefined __func__ variable (11.4.1).  */
+	/* For a constant template parameter of reference or pointer type,
+	   or for each non-static data member of reference or pointer type
+	   in a constant template parameter of class type or subobject thereof,
+	   the reference or pointer value shall not refer or point to
+	   (respectively):
+	   -- a temporary object,
+	   -- a string literal object,
+	   -- the result of a typeid expression,
+	   -- a predefined __func__ variable, or
+	   -- a subobject of one of the above.  */
 	else if (VAR_P (decl) && DECL_ARTIFICIAL (decl)
 		 && !DECL_NTTP_OBJECT_P (decl))
 	  {
-	    gcc_checking_assert (DECL_TINFO_P (decl) || DECL_FNAME_P (decl));
+	    gcc_checking_assert (DECL_TINFO_P (decl)
+				 || DECL_FNAME_P (decl)
+				 || DECL_IGNORED_P (decl));
 	    if (complain & tf_error)
 	      error ("the address of %qD is not a valid template argument",
 		     decl);
diff --git a/gcc/testsuite/g++.dg/cpp1z/nontype-auto27.C b/gcc/testsuite/g++.dg/cpp1z/nontype-auto27.C
new file mode 100644
index 00000000000..51ff86dfc25
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/nontype-auto27.C
@@ -0,0 +1,5 @@
+// PR c++/115181
+// { dg-do compile { target c++17 } }
+
+template <auto> struct S {};
+__extension__ S<(int[]){1}> x;  // { dg-error "not a valid template argument" }
diff --git a/gcc/testsuite/g++.dg/cpp1z/nontype-auto28.C b/gcc/testsuite/g++.dg/cpp1z/nontype-auto28.C
new file mode 100644
index 00000000000..d9165f87987
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/nontype-auto28.C
@@ -0,0 +1,14 @@
+// PR c++/125043
+// { dg-do compile { target c++17 } }
+
+template <auto V>
+struct wrapper {
+    static constexpr const auto& value = V;
+};
+
+template <int const& I>
+auto f() -> void;
+
+auto main() -> int {
+    f<wrapper<42>::value>();  // { dg-error "no matching function|not a valid template argument" }
+}
diff --git a/gcc/testsuite/g++.dg/cpp2a/nontype-class75.C b/gcc/testsuite/g++.dg/cpp2a/nontype-class75.C
new file mode 100644
index 00000000000..a30ccbee85d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/nontype-class75.C
@@ -0,0 +1,34 @@
+// PR c++/124979
+// { dg-do compile { target c++20 } }
+
+template<auto X, class = decltype(X)>
+struct cw;
+
+struct base {
+
+    template <class L>
+    friend constexpr auto operator &(L) noexcept
+        -> cw<(&L::value)> {
+        return {};
+    }
+};
+
+template<auto X, class>
+struct cw : base {
+    static constexpr const auto& value = X;
+};
+    template <auto L, auto R>
+    constexpr auto operator ->*(cw<L>, cw<R>) noexcept
+        -> cw<L ->* R> {
+        return {};
+    }
+
+struct Divide { int value; };
+auto cvalue = cw<&Divide::value>{};
+constexpr const Divide &t = {42};
+auto co = cw<Divide{42}>{};
+auto co1 = cw<&t>{};  // { dg-error "not a valid template argument|is invalid" }
+
+template<class> class TD;
+template<int t> class TD<cw<t>>{};
+TD<decltype((co1)->*cvalue)> _;	  // { dg-error "is invalid" }