On Mon, Aug 29, 2022 at 05:15:26PM -0400, Jason Merrill wrote: > On 8/29/22 04:15, Jakub Jelinek wrote: > > Hi! > > > > The following patch introduces a new warning - -Winvalid-utf8 similarly > > to what clang now has - to diagnose invalid UTF-8 byte sequences in > > comments. In identifiers and in string literals it should be diagnosed > > already but comment content hasn't been really verified. > > > > I'm not sure if this is enough to say P2295R6 is implemented or not. > > > > The problem is that in the most common case, people don't use > > -finput-charset= option and the sources often are UTF-8, but sometimes > > could be some ASCII compatible single byte encoding where non-ASCII > > characters only appear in comments. So having the warning off by default > > is IMO desirable. Now, if people use explicit -finput-charset=UTF-8, > > perhaps we could make the warning on by default for C++23 and use pedwarn > > instead of warning, because then the user told us explicitly that the source > > is UTF-8. From the paper I understood one of the implementation options > > is to claim that the implementation supports 2 encodings, UTF-8 and UTF-8 > > like encodings where invalid UTF-8 characters in comments are replaced say > > by spaces, where the latter could be the default and the former only > > used if -finput-charset=UTF-8 -Werror=invalid-utf8 options are used. > > > > Thoughts on this? > > That sounds good to me.
The pedwarn on -std=c++23 -finput-charset=UTF-8 or just documenting that "conforming" UTF-8 is only -finput-charset=UTF-8 -Werror=invalid-utf8 ? > > +static const uchar * > > +_cpp_warn_invalid_utf8 (cpp_reader *pfile) > > +{ > > + cpp_buffer *buffer = pfile->buffer; > > + const uchar *cur = buffer->cur; > > + > > + if (cur[0] < utf8_signifier > > + || cur[1] < utf8_continuation || cur[1] >= utf8_signifier) > > + { > > + cpp_warning_with_line (pfile, CPP_W_INVALID_UTF8, > > + pfile->line_table->highest_line, > > + CPP_BUF_COL (buffer), > > + "invalid UTF-8 character <%x> in comment", > > + cur[0]); > > + return cur + 1; > > + } > > + else if (cur[2] < utf8_continuation || cur[2] >= utf8_signifier) > > Unicode table 3-7 says that the second byte is sometimes restricted to less > than this range. That is true and I've tried to include tests for all of those cases in the testcase and all of them get a warning. Some of them are through: /* Make sure the shortest possible encoding was used. */ if (c <= 0x7F && nbytes > 1) return EILSEQ; if (c <= 0x7FF && nbytes > 2) return EILSEQ; if (c <= 0xFFFF && nbytes > 3) return EILSEQ; if (c <= 0x1FFFFF && nbytes > 4) return EILSEQ; if (c <= 0x3FFFFFF && nbytes > 5) return EILSEQ; and others are through: /* Make sure the character is valid. */ if (c > 0x7FFFFFFF || (c >= 0xD800 && c <= 0xDFFF)) return EILSEQ; All I had to do outside of what one_utf8_to_cppchar already implements was: > > + if (_cpp_valid_utf8 (pfile, &pstr, buffer->rlimit, 0, NULL, &s) > > + && s <= 0x0010FFFF) the <= 0x0010FFFF check, because one_utf8_to_cppchar as written happily supports up to 6 bytes long UTF-8 which can encode up to 7FFFFFFF: 00000000-0000007F 0xxxxxxx 00000080-000007FF 110xxxxx 10xxxxxx 00000800-0000FFFF 1110xxxx 10xxxxxx 10xxxxxx 00010000-001FFFFF 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx 00200000-03FFFFFF 111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 04000000-7FFFFFFF 1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx while 3-7 only talks about encoding 0..D7FF and D800..10FFFF in up to 4 bytes. I guess I should try what happens with 0x110000 and 0x7fffffff in identifiers and string literals. Jakub