[PATCH 2/2] utf8: add comment explaining why BOMs are rejected
From: brian m. carlson <hidden>
Date: 2018-12-27 02:17:52
Subsystem:
the rest · Maintainer:
Linus Torvalds
A source of confusion for many Git users is why UTF-16LE and UTF-16BE do not allow a BOM, instead treating it as a ZWNBSP, according to the Unicode FAQ[0]. Explain in a comment why we cannot allow that to occur due to our use of UTF-8 internally. [0] https://unicode.org/faq/utf_bom.html#bom9 Signed-off-by: brian m. carlson <redacted> --- utf8.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/utf8.c b/utf8.c
index eb78587504..22af2c485a 100644
--- a/utf8.c
+++ b/utf8.c@@ -571,6 +571,13 @@ static const char utf16_le_bom[] = {'\xFF', '\xFE'}; static const char utf32_be_bom[] = {'\0', '\0', '\xFE', '\xFF'}; static const char utf32_le_bom[] = {'\xFF', '\xFE', '\0', '\0'}; +/* + * We check here for a forbidden BOM. When using UTF-16BE or UTF-16LE, a BOM is + * not allowed by RFC 2781, and any U+FEFF would be treated as a ZWNBSP, not a + * BOM. However, because we encode into UTF-8 internally, we cannot allow that + * character to occur as a ZWNBSP, since when encoded into UTF-8 it would be + * interpreted as a BOM. + */ int has_prohibited_utf_bom(const char *enc, const char *data, size_t len) { return (