From: Jason Merrill <jason@redhat.com>
Date: Thu, 18 Sep 2025 11:10:54 +0000 (+0200)
Subject: c++: -Wmismatched-new-delete, -O0, new (nothrow)
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c91e508a52d4441b6c081ea50b0a08d0f4775675;p=thirdparty%2Fgcc.git

c++: -Wmismatched-new-delete, -O0, new (nothrow)

With new (nothrow) we need to check whether the allocation returned null,
and the resulting COND_EXPR was confusing -Wmismatched-new-delete-2 at -O0.
Let's help it out by appending the address if it's the same on both arms.

gcc/cp/ChangeLog:

	* init.cc (build_new_1): Append alloc_node to checking COND_EXPR.

gcc/testsuite/ChangeLog:

	* g++.dg/warn/Wmismatched-new-delete-2.C: Remove xfail.
---

diff --git a/gcc/cp/init.cc b/gcc/cp/init.cc
index f19794caadc..8db84eb5e38 100644
--- a/gcc/cp/init.cc
+++ b/gcc/cp/init.cc
@@ -3930,6 +3930,11 @@ build_new_1 (vec<tree, va_gc> **placement, tree type, tree nelts,
 					   complain);
 	  rval = build_conditional_expr (input_location, ifexp, rval,
 					 alloc_node, complain);
+	  /* If there's no offset between data_addr and alloc_node, append it
+	     to help -Wmismatched-new-delete at -O0.  */
+	  if (!cookie_size)
+	    rval = build2 (COMPOUND_EXPR, TREE_TYPE (alloc_node),
+			   rval, alloc_node);
 	}
 
       /* Perform the allocation before anything else, so that ALLOC_NODE
diff --git a/gcc/testsuite/g++.dg/warn/Wmismatched-new-delete-2.C b/gcc/testsuite/g++.dg/warn/Wmismatched-new-delete-2.C
index d0d53b38b93..0f1877ee3e5 100644
--- a/gcc/testsuite/g++.dg/warn/Wmismatched-new-delete-2.C
+++ b/gcc/testsuite/g++.dg/warn/Wmismatched-new-delete-2.C
@@ -140,9 +140,8 @@ void warn_x1_array_mismatch ()
     delete p;                 // { dg-warning "'static void X1::operator delete\\(void\\*\\)' called on pointer returned from a mismatched allocation function" }
   }
   {
-    // The following requires optimization (see warn_x1_array_mismatch()).
     X1 *p = new (std::nothrow) X1[3];
-    delete p;                 // { dg-warning "'static void X1::operator delete\\(void\\*\\)' called on pointer returned from a mismatched allocation function" "pr?????" { xfail *-*-* } }
+    delete p;                 // { dg-warning "'static void X1::operator delete\\(void\\*\\)' called on pointer returned from a mismatched allocation function" }
   }
 }