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Diffstat (limited to 'gcc/doc/invoke.texi')
| -rw-r--r-- | gcc/doc/invoke.texi | 56 |
1 files changed, 55 insertions, 1 deletions
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi index 5ed1d13..1151708 100644 --- a/gcc/doc/invoke.texi +++ b/gcc/doc/invoke.texi @@ -206,7 +206,7 @@ in the following sections. @item C++ Language Options @xref{C++ Dialect Options,,Options Controlling C++ Dialect}. @gccoptlist{-fabi-version=@var{n} -fno-access-control @gol --faligned-new=@var{n} -fargs-in-order=@var{n} -fcheck-new @gol +-faligned-new=@var{n} -fargs-in-order=@var{n} -fchar8_t -fcheck-new @gol -fconstexpr-depth=@var{n} -fconstexpr-loop-limit=@var{n} @gol -fno-elide-constructors @gol -fno-enforce-eh-specs @gol @@ -2426,6 +2426,60 @@ but few users will need to override the default of This flag is enabled by default for @option{-std=c++17}. +@item -fchar8_t +@itemx -fno-char8_t +@opindex fchar8_t +@opindex fno-char8_t +Enable support for @code{char8_t} as adopted for C++2a. This includes +the addition of a new @code{char8_t} fundamental type, changes to the +types of UTF-8 string and character literals, new signatures for +user-defined literals, associated standard library updates, and new +@code{__cpp_char8_t} and @code{__cpp_lib_char8_t} feature test macros. + +This option enables functions to be overloaded for ordinary and UTF-8 +strings: + +@smallexample +int f(const char *); // #1 +int f(const char8_t *); // #2 +int v1 = f("text"); // Calls #1 +int v2 = f(u8"text"); // Calls #2 +@end smallexample + +@noindent +and introduces new signatures for user-defined literals: + +@smallexample +int operator""_udl1(char8_t); +int v3 = u8'x'_udl1; +int operator""_udl2(const char8_t*, std::size_t); +int v4 = u8"text"_udl2; +template<typename T, T...> int operator""_udl3(); +int v5 = u8"text"_udl3; +@end smallexample + +@noindent +The change to the types of UTF-8 string and character literals introduces +incompatibilities with ISO C++11 and later standards. For example, the +following code is well-formed under ISO C++11, but is ill-formed when +@option{-fchar8_t} is specified. + +@smallexample +char ca[] = u8"xx"; // error: char-array initialized from wide + // string +const char *cp = u8"xx";// error: invalid conversion from + // `const char8_t*' to `const char*' +int f(const char*); +auto v = f(u8"xx"); // error: invalid conversion from + // `const char8_t*' to `const char*' +std::string s@{u8"xx"@}; // error: no matching function for call to + // `std::basic_string<char>::basic_string()' +using namespace std::literals; +s = u8"xx"s; // error: conversion from + // `basic_string<char8_t>' to non-scalar + // type `basic_string<char>' requested +@end smallexample + @item -fcheck-new @opindex fcheck-new Check that the pointer returned by @code{operator new} is non-null |