From: Patrick Palka <ppalka@redhat.com>
Date: Thu, 12 Feb 2026 19:44:56 +0000 (-0500)
Subject: c++: evaluation order of xobj memfn call [PR123989]
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0d51ed19504bcaa540763423763bb97227ed6c1c;p=thirdparty%2Fgcc.git

c++: evaluation order of xobj memfn call [PR123989]

The object argument of an xobj memfn call needs to be evaluated before its
formal arguments, like with an iobj memfn call.  This patch generalizes the
existing such handling in cp_gimplify_expr for METHOD_TYPE callees to also
accept xobj memfn callees.

	PR c++/123989

gcc/cp/ChangeLog:

	* cp-gimplify.cc (cp_gimplify_expr) <case CALL_EXPR>: Evaluate
	the object argument of an xobj memfn call first too.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp23/explicit-obj-eval-order.C: New test.

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

diff --git a/gcc/cp/cp-gimplify.cc b/gcc/cp/cp-gimplify.cc
index 9d96ce99ea9..2e2f328079a 100644
--- a/gcc/cp/cp-gimplify.cc
+++ b/gcc/cp/cp-gimplify.cc
@@ -921,7 +921,14 @@ cp_gimplify_expr (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p)
 	  tree fntype = TREE_TYPE (CALL_EXPR_FN (*expr_p));
 	  if (INDIRECT_TYPE_P (fntype))
 	    fntype = TREE_TYPE (fntype);
-	  if (TREE_CODE (fntype) == METHOD_TYPE)
+	  tree decl = cp_get_callee_fndecl_nofold (*expr_p);
+	  /* We can't just rely on 'decl' because virtual function callees
+	     are expressed as OBJ_TYPE_REF.  Though checking for METHOD_TYPE
+	     means we'll also sequence PMF calls, which is allowed under
+	     "indeterminately sequenced".  */
+	  if (TREE_CODE (fntype) == METHOD_TYPE
+	      || (decl && DECL_LANG_SPECIFIC (decl)
+		  && DECL_XOBJ_MEMBER_FUNCTION_P (decl)))
 	    {
 	      int nargs = call_expr_nargs (*expr_p);
 	      bool side_effects = false;
diff --git a/gcc/testsuite/g++.dg/cpp23/explicit-obj-eval-order.C b/gcc/testsuite/g++.dg/cpp23/explicit-obj-eval-order.C
new file mode 100644
index 00000000000..7ce81f32cc4
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp23/explicit-obj-eval-order.C
@@ -0,0 +1,16 @@
+// PR c++/123989
+// { dg-do run { target c++23 } }
+
+struct A {
+  int m = 42;
+
+  void f(this A self, int n) {
+    if (self.m != 42 || n != 43)
+      __builtin_abort();
+  }
+};
+
+int main() {
+  A a;
+  a.f(++a.m);
+}