[flang-commits] [flang] [flang] Fix -Wcharacter-conversion warnings (NFC) (PR #155873)

[Michael Kruse via flang-commits]

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@@ -289,7 +289,8 @@ RESULT DecodeString(const std::string &s, bool backslashEscapes) {
         DecodeCharacter<ENCODING>(p, bytes, backslashEscapes)};
     if (decoded.bytes > 0) {
       if (static_cast<std::size_t>(decoded.bytes) <= bytes) {
-        result.append(1, decoded.codepoint);
+        result.append(
+            1, static_cast<typename RESULT::value_type>(decoded.codepoint));
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Meinersbur wrote:

There is the overload `std::u16string DecodeString<std::u16string, Encoding::UTF_8>`. A character outside the unicode basic plane needs more than 16 bits. 

According to https://flang.llvm.org/docs/Character.html#kinds-and-character-sets, Fortran strings are expected to be UCS-2 and truncation is expected.

> In particular, conversions between kinds are assumed to be simple zero-extensions or truncation, not table look-ups.

https://github.com/llvm/llvm-project/pull/155873