Re: [PATCH 3/3] c++/106426: Treat u8 character literals as unsigned in char8_t modes.

[Andrew Pinski <pinskia@gmail.com>]

On Mon, Jul 25, 2022 at 11:01 AM Tom Honermann via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> This patch corrects handling of UTF-8 character literals in preprocessing
> directives so that they are treated as unsigned types in char8_t enabled
> C++ modes (C++17 with -fchar8_t or C++20 without -fno-char8_t). Previously,
> UTF-8 character literals were always treated as having the same type as
> ordinary character literals (signed or unsigned dependent on target or use
> of the -fsigned-char or -funsigned char options).
>
> Fixes https://gcc.gnu.org/PR106426.

The above mention of the PR # should just be:
preprocessor/106426

And then when this patch gets committed, it will be recorded in bugzilla also.

Thanks,
Andrew Pinski

>
> gcc/c-family/ChangeLog:
>         * c-opts.cc (c_common_post_options): Assign cpp_opts->unsigned_utf8char
>         subject to -fchar8_t, -fsigned-char, and/or -funsigned-char.
>
> gcc/testsuite/ChangeLog:
>         * g++.dg/ext/char8_t-char-literal-1.C: Check signedness of u8 literals.
>         * g++.dg/ext/char8_t-char-literal-2.C: Check signedness of u8 literals.
>
> libcpp/ChangeLog:
>         * charset.cc (narrow_str_to_charconst): Set signedness of CPP_UTF8CHAR
>         literals based on unsigned_utf8char.
>         * include/cpplib.h (cpp_options): Add unsigned_utf8char.
>         * init.cc (cpp_create_reader): Initialize unsigned_utf8char.
> ---
>  gcc/c-family/c-opts.cc                            | 1 +
>  gcc/testsuite/g++.dg/ext/char8_t-char-literal-1.C | 6 +++++-
>  gcc/testsuite/g++.dg/ext/char8_t-char-literal-2.C | 4 ++++
>  libcpp/charset.cc                                 | 4 ++--
>  libcpp/include/cpplib.h                           | 4 ++--
>  libcpp/init.cc                                    | 1 +
>  6 files changed, 15 insertions(+), 5 deletions(-)
>
> diff --git a/gcc/c-family/c-opts.cc b/gcc/c-family/c-opts.cc
> index 108adc5caf8..02ce1e86cdb 100644
> --- a/gcc/c-family/c-opts.cc
> +++ b/gcc/c-family/c-opts.cc
> @@ -1062,6 +1062,7 @@ c_common_post_options (const char **pfilename)
>    /* char8_t support is implicitly enabled in C++20 and C2X.  */
>    if (flag_char8_t == -1)
>      flag_char8_t = (cxx_dialect >= cxx20) || flag_isoc2x;
> +  cpp_opts->unsigned_utf8char = flag_char8_t ? 1 : cpp_opts->unsigned_char;
>
>    if (flag_extern_tls_init)
>      {
> diff --git a/gcc/testsuite/g++.dg/ext/char8_t-char-literal-1.C b/gcc/testsuite/g++.dg/ext/char8_t-char-literal-1.C
> index 8ed85ccfdcd..2994dd38516 100644
> --- a/gcc/testsuite/g++.dg/ext/char8_t-char-literal-1.C
> +++ b/gcc/testsuite/g++.dg/ext/char8_t-char-literal-1.C
> @@ -1,6 +1,6 @@
>  // Test that UTF-8 character literals have type char if -fchar8_t is not enabled.
>  // { dg-do compile }
> -// { dg-options "-std=c++17 -fno-char8_t" }
> +// { dg-options "-std=c++17 -fsigned-char -fno-char8_t" }
>
>  template<typename T1, typename T2>
>    struct is_same
> @@ -10,3 +10,7 @@ template<typename T>
>    { static const bool value = true; };
>
>  static_assert(is_same<decltype(u8'x'), char>::value, "Error");
> +
> +#if u8'\0' - 1 > 0
> +#error "UTF-8 character literals not signed in preprocessor"
> +#endif
> diff --git a/gcc/testsuite/g++.dg/ext/char8_t-char-literal-2.C b/gcc/testsuite/g++.dg/ext/char8_t-char-literal-2.C
> index 7861736689c..db4fe70046d 100644
> --- a/gcc/testsuite/g++.dg/ext/char8_t-char-literal-2.C
> +++ b/gcc/testsuite/g++.dg/ext/char8_t-char-literal-2.C
> @@ -10,3 +10,7 @@ template<typename T>
>    { static const bool value = true; };
>
>  static_assert(is_same<decltype(u8'x'), char8_t>::value, "Error");
> +
> +#if u8'\0' - 1 < 0
> +#error "UTF-8 character literals not unsigned in preprocessor"
> +#endif
> diff --git a/libcpp/charset.cc b/libcpp/charset.cc
> index ca8b7cf7aa5..12e31632228 100644
> --- a/libcpp/charset.cc
> +++ b/libcpp/charset.cc
> @@ -1960,8 +1960,8 @@ narrow_str_to_charconst (cpp_reader *pfile, cpp_string str,
>    /* Multichar constants are of type int and therefore signed.  */
>    if (i > 1)
>      unsigned_p = 0;
> -  else if (type == CPP_UTF8CHAR && !CPP_OPTION (pfile, cplusplus))
> -    unsigned_p = 1;
> +  else if (type == CPP_UTF8CHAR)
> +    unsigned_p = CPP_OPTION (pfile, unsigned_utf8char);
>    else
>      unsigned_p = CPP_OPTION (pfile, unsigned_char);
>
> diff --git a/libcpp/include/cpplib.h b/libcpp/include/cpplib.h
> index 3eba6f74b57..f9c042db034 100644
> --- a/libcpp/include/cpplib.h
> +++ b/libcpp/include/cpplib.h
> @@ -581,8 +581,8 @@ struct cpp_options
>       ints and target wide characters, respectively.  */
>    size_t precision, char_precision, int_precision, wchar_precision;
>
> -  /* True means chars (wide chars) are unsigned.  */
> -  bool unsigned_char, unsigned_wchar;
> +  /* True means chars (wide chars, UTF-8 chars) are unsigned.  */
> +  bool unsigned_char, unsigned_wchar, unsigned_utf8char;
>
>    /* True if the most significant byte in a word has the lowest
>       address in memory.  */
> diff --git a/libcpp/init.cc b/libcpp/init.cc
> index f4ab83d2145..0242da5f55c 100644
> --- a/libcpp/init.cc
> +++ b/libcpp/init.cc
> @@ -231,6 +231,7 @@ cpp_create_reader (enum c_lang lang, cpp_hash_table *table,
>    CPP_OPTION (pfile, int_precision) = CHAR_BIT * sizeof (int);
>    CPP_OPTION (pfile, unsigned_char) = 0;
>    CPP_OPTION (pfile, unsigned_wchar) = 1;
> +  CPP_OPTION (pfile, unsigned_utf8char) = 1;
>    CPP_OPTION (pfile, bytes_big_endian) = 1;  /* does not matter */
>
>    /* Default to no charset conversion.  */
> --
> 2.32.0
>