[PATCH v4 1/3] libcpp: reject codepoints above 0x10FFFF

[Ben Boeckel <ben.boeckel@kitware.com>]

Unicode does not support such values because they are unrepresentable in
UTF-16.

libcpp/

	* charset.cc: Reject encodings of codepoints above 0x10FFFF.
	UTF-16 does not support such codepoints and therefore all
	Unicode rejects such values.

Signed-off-by: Ben Boeckel <ben.boeckel@kitware.com>
---
 libcpp/charset.cc | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/libcpp/charset.cc b/libcpp/charset.cc
index 12a398e7527..324b5b19136 100644
--- a/libcpp/charset.cc
+++ b/libcpp/charset.cc
@@ -158,6 +158,10 @@ struct _cpp_strbuf
    encoded as any of DF 80, E0 9F 80, F0 80 9F 80, F8 80 80 9F 80, or
    FC 80 80 80 9F 80.  Only the first is valid.
 
+   Additionally, Unicode declares that all codepoints above 0010FFFF are
+   invalid because they cannot be represented in UTF-16. As such, all 5- and
+   6-byte encodings are invalid.
+
    An implementation note: the transformation from UTF-16 to UTF-8, or
    vice versa, is easiest done by using UTF-32 as an intermediary.  */
 
@@ -216,7 +220,7 @@ one_utf8_to_cppchar (const uchar **inbufp, size_t *inbytesleftp,
   if (c <= 0x3FFFFFF && nbytes > 5) return EILSEQ;
 
   /* Make sure the character is valid.  */
-  if (c > 0x7FFFFFFF || (c >= 0xD800 && c <= 0xDFFF)) return EILSEQ;
+  if (c > 0x10FFFF || (c >= 0xD800 && c <= 0xDFFF)) return EILSEQ;
 
   *cp = c;
   *inbufp = inbuf;
@@ -320,7 +324,7 @@ one_utf32_to_utf8 (iconv_t bigend, const uchar **inbufp, size_t *inbytesleftp,
   s += inbuf[bigend ? 2 : 1] << 8;
   s += inbuf[bigend ? 3 : 0];
 
-  if (s >= 0x7FFFFFFF || (s >= 0xD800 && s <= 0xDFFF))
+  if (s > 0x10FFFF || (s >= 0xD800 && s <= 0xDFFF))
     return EILSEQ;
 
   rval = one_cppchar_to_utf8 (s, outbufp, outbytesleftp);
-- 
2.38.1