mirror/gcc
2
0
Fork 0
mirror of git://gcc.gnu.org/git/gcc.git synced 2025-04-21 14:30:59 +08:00
Code Issues Packages Projects Releases Wiki Activity

libstdc++: Improve diagnostics for invalid std::format calls

Browse Source 
Add a static_assert and a comment so that calling std::format for
unformattable argument types will now show:

/home/jwakely/gcc/13/include/c++/13.0.1/format:3563:22: error: static assertion failed: std::formatter must be specialized for each format arg
 3563 |       static_assert((is_default_constructible_v<formatter<_Args, _CharT>> && ...),
      |                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

and:

  140 |       formatter() = delete; // No std::formatter specialization for this type.

libstdc++-v3/ChangeLog:

	* include/std/format (formatter): Add comment to deleted default
	constructor of primary template.
	(_Checking_scanner): Add static_assert.
This commit is contained in:
Jonathan Wakely 2023-04-13 16:34:51 +01:00
parent b0e85485fb
commit 6a9547f3ca
1 changed files with 9 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
libstdc++-v3/include/std/format
View File

@ -137,7 +137,7 @@ namespace __format
template<typename _Tp, typename _CharT = char>
struct formatter
{
formatter() = delete;
formatter() = delete; // No std::formatter specialization for this type.
formatter(const formatter&) = delete;
formatter& operator=(const formatter&) = delete;
};
@ -3560,6 +3560,10 @@ namespace __format
template<typename _CharT, typename... _Args>
class _Checking_scanner : public _Scanner<_CharT>
{
static_assert(
(is_default_constructible_v<formatter<_Args, _CharT>> && ...),
"std::formatter must be specialized for each type being formatted");
public:
constexpr
_Checking_scanner(basic_string_view<_CharT> __str)
@ -3581,17 +3585,17 @@ namespace __format
__builtin_unreachable();
}
template<typename _Head, typename... _Tail>
template<typename _Tp, typename... _OtherArgs>
constexpr void
_M_parse_format_spec(size_t __id)
{
if (__id == 0)
{
formatter<_Head, _CharT> __f;
formatter<_Tp, _CharT> __f;
this->_M_pc.advance_to(__f.parse(this->_M_pc));
}
else if constexpr (sizeof...(_Tail) != 0)
_M_parse_format_spec<_Tail...>(__id - 1);
else if constexpr (sizeof...(_OtherArgs) != 0)
_M_parse_format_spec<_OtherArgs...>(__id - 1);
else
__builtin_unreachable();
}