Fix mistaken uses of memcpy() on overlapping memory.

The source and destination arguments to memcpy() cannot be overlapping
as this is undefined behavior. In these situations memmove() must be
used instead, and OpenBSD actually throws an error if this is done.

Thanks to ryan-sg for reporting this. This fixes #510.

3 files changed, 5 insertions, 4 deletions

diff --git a/src/net_client.c b/src/net_client.c
index e0037e3e..ac81e367 100644
--- a/src/net_client.c
+++ b/src/net_client.c
@@ -279,8 +279,8 @@ static void NET_CL_AdvanceWindow(void)
 
         // Advance the window
 
-        memcpy(recvwindow, recvwindow + 1, 
-               sizeof(net_server_recv_t) * (BACKUPTICS - 1));
+        memmove(recvwindow, recvwindow + 1,
+                sizeof(net_server_recv_t) * (BACKUPTICS - 1));
         memset(&recvwindow[BACKUPTICS-1], 0, sizeof(net_server_recv_t));
 
         ++recvwindow_start;
diff --git a/src/net_server.c b/src/net_server.c
index b4496bb5..b3ec1693 100644
--- a/src/net_server.c
+++ b/src/net_server.c
@@ -514,7 +514,8 @@ static void NET_SV_AdvanceWindow(void)
         
         // Advance the window
 
-        memcpy(recvwindow, recvwindow + 1, sizeof(*recvwindow) * (BACKUPTICS - 1));
+        memmove(recvwindow, recvwindow + 1,
+                sizeof(*recvwindow) * (BACKUPTICS - 1));
         memset(&recvwindow[BACKUPTICS-1], 0, sizeof(*recvwindow));
         ++recvwindow_start;
 
diff --git a/src/net_structrw.c b/src/net_structrw.c
index 60316dc7..a820df5f 100644
--- a/src/net_structrw.c
+++ b/src/net_structrw.c
@@ -316,7 +316,7 @@ void NET_TiccmdDiff(ticcmd_t *tic1, ticcmd_t *tic2, net_ticdiff_t *diff)
 
 void NET_TiccmdPatch(ticcmd_t *src, net_ticdiff_t *diff, ticcmd_t *dest)
 {
-    memcpy(dest, src, sizeof(ticcmd_t));
+    memmove(dest, src, sizeof(ticcmd_t));
 
     // Apply the diff