From: Maarten ter Huurne <maarten@treewalker.org>
Date: Sat, 13 Sep 2014 11:37:59 +0200
Subject: Do not use memcpy as an alternative for bcopy/memmove

The configure script runs a small test program to check whether
memcpy can handle overlapping memory areas. However, it is not valid
to conclude that if a single case of overlapping memory is handled
correctly, all cases will be handled correctly.

Since screen already has its own bcopy implementation as a fallback
for the case that bcopy and memmove are unusable, removing the memcpy
option should not break any systems.

Signed-off-by: Maarten ter Huurne <maarten@treewalker.org>
---
 acconfig.h   |  3 +--
 configure.in | 18 +-----------------
 os.h         |  8 ++------
 osdef.h.in   | 10 +---------
 4 files changed, 5 insertions(+), 34 deletions(-)

diff --git a/acconfig.h b/acconfig.h
index 2e46985..9b0b9d4 100644
--- a/acconfig.h
+++ b/acconfig.h
@@ -476,7 +476,7 @@
 #undef GETTTYENT
 
 /*
- * Define USEBCOPY if the bcopy/memcpy from your system's C library
+ * Define USEBCOPY if the bcopy from your system's C library
  * supports the overlapping of source and destination blocks.  When
  * undefined, screen uses its own (probably slower) version of bcopy().
  * 
@@ -487,7 +487,6 @@
  * Their memove fails the test in the configure script. Sigh. (Juergen)
  */
 #undef USEBCOPY
-#undef USEMEMCPY
 #undef USEMEMMOVE
 
 /*
diff --git a/configure.in b/configure.in
index 572c2a3..ff9606d 100644
--- a/configure.in
+++ b/configure.in
@@ -1144,7 +1144,7 @@ AC_TRY_LINK(,[getttyent();], AC_DEFINE(GETTTYENT))
 AC_CHECKING(fdwalk)
 AC_TRY_LINK([#include <stdlib.h>], [fdwalk(NULL, NULL);],AC_DEFINE(HAVE_FDWALK))
 
-AC_CHECKING(whether memcpy/memmove/bcopy handles overlapping arguments)
+AC_CHECKING(whether memmove/bcopy handles overlapping arguments)
 AC_TRY_RUN([
 main() {
   char buf[10];
@@ -1174,22 +1174,6 @@ main() {
   exit(0); /* libc version works properly.  */
 }], AC_DEFINE(USEMEMMOVE))
 
-
-AC_TRY_RUN([
-#define bcopy(s,d,l) memcpy(d,s,l)
-main() {
-  char buf[10];
-  strcpy(buf, "abcdefghi");
-  bcopy(buf, buf + 2, 3);
-  if (strncmp(buf, "ababcf", 6))
-    exit(1);
-  strcpy(buf, "abcdefghi");
-  bcopy(buf + 2, buf, 3);
-  if (strncmp(buf, "cdedef", 6))
-    exit(1);
-  exit(0); /* libc version works properly.  */
-}], AC_DEFINE(USEMEMCPY))
-
 AC_SYS_LONG_FILE_NAMES
 
 AC_MSG_CHECKING(for vsprintf)
diff --git a/os.h b/os.h
index 55de249..6838ec0 100644
--- a/os.h
+++ b/os.h
@@ -142,12 +142,8 @@ extern int errno;
 # ifdef USEMEMMOVE
 #  define bcopy(s,d,len) memmove(d,s,len)
 # else
-#  ifdef USEMEMCPY
-#   define bcopy(s,d,len) memcpy(d,s,len)
-#  else
-#   define NEED_OWN_BCOPY
-#   define bcopy xbcopy
-#  endif
+#  define NEED_OWN_BCOPY
+#  define bcopy xbcopy
 # endif
 #endif
 
diff --git a/osdef.h.in b/osdef.h.in
index 8687b60..e4057a0 100644
--- a/osdef.h.in
+++ b/osdef.h.in
@@ -58,16 +58,8 @@ extern int   bcmp __P((char *, char *, int));
 extern int   killpg __P((int, int));
 #endif
 
-#ifndef USEBCOPY
-# ifdef USEMEMCPY
-extern void  memcpy __P((char *, char *, int));
-# else
-#  ifdef USEMEMMOVE
+#if defined(USEMEMMOVE) && !defined(USEBCOPY)
 extern void  memmove __P((char *, char *, int));
-#  else
-extern void  bcopy __P((char *, char *, int));
-#  endif
-# endif
 #else
 extern void  bcopy __P((char *, char *, int));
 #endif
-- 
1.8.4.5