[PATCH 11/13] gdb/remote-fileio: remove uses of sprintf

When building on macOS, I get some:

    /Users/smarchi/src/binutils-gdb/gdb/remote-fileio.c:264:3: error: 'sprintf' is deprecated: This function is provided for compatibility reasons only.  Due to security concerns inherent in the design of sprintf(3), it is highly recommended that you use snprintf(3) instead. [-Werror,-Wdeprecated-declarations]
      264 |   sprintf (buf + strlen (buf), "%x", retcode);
          |   ^

The reply built in remote_fileio_reply is made by appending to a fixed
size buffer, using a mix of strcpy, strcat and sprintf.  Replace them
with the safer xsnprintf and xstrcpy.  This way, every write is bounds
checked.

Change-Id: I8446a98be5c5fc0eda79ccbc4858d9dddaf2d4d5
---
 gdb/remote-fileio.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/gdb/remote-fileio.c b/gdb/remote-fileio.c
index a151161371da..297e3337e2fe 100644
--- a/gdb/remote-fileio.c
+++ b/gdb/remote-fileio.c
@@ -253,28 +253,37 @@ static void
 remote_fileio_reply (remote_target *remote, int retcode, int error)
 {
   char buf[32];
+  char *p = buf;
+  char *const end = buf + sizeof (buf);
   bool ctrl_c = check_quit_flag ();
 
-  strcpy (buf, "F");
+  p += xstrcpy (p, end - p, "F");
+
   if (retcode < 0)
     {
-      strcat (buf, "-");
+      p += xstrcpy (p, end - p, "-");
       retcode = -retcode;
     }
-  sprintf (buf + strlen (buf), "%x", retcode);
+
+  p += xsnprintf (p, end - p, "%x", retcode);
+
   if (error || ctrl_c)
     {
       if (error && ctrl_c)
 	error = FILEIO_EINTR;
+
       if (error < 0)
 	{
-	  strcat (buf, "-");
+	  p += xstrcpy (p, end - p, "-");
 	  error = -error;
 	}
-      sprintf (buf + strlen (buf), ",%x", error);
+
+      p += xsnprintf (p, end - p, ",%x", error);
+
       if (ctrl_c)
-	strcat (buf, ",C");
+	p += xstrcpy (p, end - p, ",C");
     }
+
   quit_handler = remote_fileio_o_quit_handler;
   putpkt (remote, buf);
 }
-- 
2.55.0