From: Marek Polacek <polacek@redhat.com>
Date: Wed, 13 Jul 2022 00:18:56 +0000 (-0400)
Subject: libcpp: Avoid pessimizing std::move [PR106272]
X-Git-Tag: basepoints/gcc-14~5518
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=86a15b266a7284f3aa1b12494a475f31416b981d;p=thirdparty%2Fgcc.git

libcpp: Avoid pessimizing std::move [PR106272]

std::move in a return statement can prevent the NRVO:
<https://developers.redhat.com/blog/2019/04/12/understanding-when-not-to-stdmove-in-c>

PR106272 reports that we have two such cases in class label_text's
member functions.  We have -Wpessimizing-move that's supposed to detect
problematic std::move uses, but in this case it didn't trigger.  I've filed
PR106276 to track that.

	PR preprocessor/106272

libcpp/ChangeLog:

	* include/line-map.h (class label_text): Don't std::move in a return
	statement.
---

diff --git a/libcpp/include/line-map.h b/libcpp/include/line-map.h
index c6379ce25b8..c434a246b13 100644
--- a/libcpp/include/line-map.h
+++ b/libcpp/include/line-map.h
@@ -1873,13 +1873,13 @@ public:
      longer-lived owner.  */
   static label_text borrow (const char *buffer)
   {
-    return std::move (label_text (const_cast <char *> (buffer), false));
+    return label_text (const_cast <char *> (buffer), false);
   }
 
   /* Create a label_text instance that takes ownership of BUFFER.  */
   static label_text take (char *buffer)
   {
-    return std::move (label_text (buffer, true));
+    return label_text (buffer, true);
   }
 
   /* Take ownership of the buffer, copying if necessary.  */