Re: [PATCH] [gdb/build] Fix cli/cli-style.c build error with C++20

[Eli Zaretskii <eliz@gnu.org>]

> From: Tom de Vries <tdevries@suse.de>
> Date: Thu, 13 Aug 2026 04:54:45 +0200
> 
> PR build/34514 reports for a C++20 build:
> ...
> cli/cli-style.c:457:37: error: conversion from ‘const char8_t [8]’ to \
>   non-scalar type ‘std::string’ {aka ‘std::__cxx11::basic_string<char>’} \
>   requested
>   457 | static std::string warning_prefix = u8"\u26A0\uFE0F ";
>       |                                     ^~~~~~~~~~~~~~~~~
> ...
> 
> The u8 literal is char[] until C++20, but char8_t[] since C++20.
> 
> Fix this by using a reinterpret_cast<const char *>.
> 
> Tested by rebuilding using GCC 15.3.0, with and without -std=c++20.
> 
> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=34514
> ---
>  gdb/cli/cli-style.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/gdb/cli/cli-style.c b/gdb/cli/cli-style.c
> index 60c00acdf43..5c26519c6d7 100644
> --- a/gdb/cli/cli-style.c
> +++ b/gdb/cli/cli-style.c
> @@ -454,7 +454,8 @@ no_emojis ()
>     - uFE0F: Variation Selector-16 (VS16)
>     The VS16 forces "Emoji" presentation.  It is needed because the default
>     presentation for Warning Sign is "Text".  Together, we get: ⚠️ .  */
> -static std::string warning_prefix = u8"\u26A0\uFE0F ";
> +static std::string warning_prefix
> +  = reinterpret_cast<const char *> (u8"\u26A0\uFE0F ");
>  
>  /* Implement 'show style warning-prefix'.  */
>  
> @@ -479,7 +480,8 @@ print_warning_prefix (ui_file *file)
>     - u274C: Cross Mark: ❌
>     No VS16 is needed because the default presentation for Cross Mark is
>     "Emoji".  */
> -static std::string error_prefix = u8"\u274C ";
> +static std::string error_prefix
> +  = reinterpret_cast<const char *> (u8"\u274C ");

Thanks.  May I suggest to add comments here explaining why we use
reinterpret_cast?  The situation with the various C++ standards
changes with time, as we require newer versions of the standard, so at
some point this will no longer be needed.  And use of reinterpret_cast
is unusual enough to raise some brows anyway.