More validatation of coding system in 'write-region'

* src/coding.c (choose_write_coding_system): More validation of
coding-system from various sources.  Suggested by Andreas Schwab
<schwab@linux-m68k.org>.  (Bug#21602)

1 files changed, 16 insertions, 7 deletions

diff --git a/src/fileio.c b/src/fileio.c
index 65aaf572fd7..15bebdf09fa 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -4593,17 +4593,26 @@ choose_write_coding_system (Lisp_Object start, Lisp_Object end, Lisp_Object file
 
       if (!force_raw_text
           && !NILP (Ffboundp (Vselect_safe_coding_system_function)))
-        /* Confirm that VAL can surely encode the current region.  */
-        val = call5 (Vselect_safe_coding_system_function,
-                     start, end, val, Qnil, filename);
+        {
+          /* Confirm that VAL can surely encode the current region.  */
+          val = call5 (Vselect_safe_coding_system_function,
+                       start, end, val, Qnil, filename);
+          CHECK_CODING_SYSTEM (val);
+        }
 
       /* If the decided coding-system doesn't specify end-of-line
          format, we use that of
          `default-buffer-file-coding-system'.  */
-      if (! using_default_coding
-          && ! NILP (BVAR (&buffer_defaults, buffer_file_coding_system)))
-        val = (coding_inherit_eol_type
-               (val, BVAR (&buffer_defaults, buffer_file_coding_system)));
+      if (! using_default_coding)
+        {
+          Lisp_Object dflt = BVAR (&buffer_defaults, buffer_file_coding_system);
+
+          if (! NILP (dflt))
+            {
+              CHECK_CODING_SYSTEM (dflt);
+              val = (coding_inherit_eol_type (val, dflt));
+            }
+        }
 
       /* If we decide not to encode text, use `raw-text' or one of its
          subsidiaries.  */