On Mon, 12 Feb 2024, Paul Keir wrote:
> A call to `basic_string::clear()` in the std::string move assignment operator
> leads to a constexpr error from an access of inactive union member
> `_M_local_buf` in the added test (`test_move()`). Changing
> `__str._M_local_buf` to `__str._M_use_local_data()` in
> `operator=(basic_string&& __str)` fixes this.
>
> Running `make check RUNTESTFLAGS="conformance.exp=21_strings/basic_string/*"`
> on x86_64-pc-linux-gnu gave unchanged summary results (# of expected passes
> 570 # of expected failures 4 # of unsupported tests 4).
>
> I don't have write access.
>
> Signed-off-by: Paul Keir <paul.k...@uws.ac.uk>
LGTM! A ChangeLog entry is missing from the commit message,
so here's one that we can use for this commit:
PR libstdc++/113294
libstdc++-v3/ChangeLog:
* include/bits/basic_string.h (basic_string::operator=): Use
_M_use_local_data() instead of _M_local_buf on the moved-from
string.
* testsuite/21_strings/basic_string/modifiers/constexpr.cc
(test_move): New test.
>
> diff --git a/libstdc++-v3/include/bits/basic_string.h
> b/libstdc++-v3/include/bits/basic_string.h
> index 43efc99bea9..8a695a494ef 100644
> --- a/libstdc++-v3/include/bits/basic_string.h
> +++ b/libstdc++-v3/include/bits/basic_string.h
> @@ -909,7 +909,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
> __str._M_capacity(__capacity);
> }
> else
> - __str._M_data(__str._M_local_buf);
> + __str._M_data(__str._M_use_local_data());
> }
> else // Need to do a deep copy
> assign(__str);
> diff --git
> a/libstdc++-v3/testsuite/21_strings/basic_string/modifiers/constexpr.cc
> b/libstdc++-v3/testsuite/21_strings/basic_string/modifiers/constexpr.cc
> index 0e28a6d4487..ad7548f3236 100644
> --- a/libstdc++-v3/testsuite/21_strings/basic_string/modifiers/constexpr.cc
> +++ b/libstdc++-v3/testsuite/21_strings/basic_string/modifiers/constexpr.cc
> @@ -50,3 +50,16 @@ test_erasure()
> }
>
> static_assert( test_erasure() );
> +
> +constexpr bool
> +test_move()
> +{
> + std::string s1;
> + std::string s2 = "1234567890123456"; // 16 chars: more than
> _S_local_capacity
> + s1 = std::move(s2);
> + VERIFY( s1 == "1234567890123456" );
> +
> + return true;
> +}
> +
> +static_assert( test_move() );
> --
>
>
> Please consider the environment and think before you print.
>
> The University of the West of Scotland is a registered Scottish charity.
> Charity number SC002520.
>
> This e-mail and any attachment is for authorised use by the intended
> recipient(s) only. It may contain proprietary material, confidential
> information and/or be subject to legal privilege. It should not be copied,
> disclosed to, retained or used by, any other party. If you are not an
> intended recipient then please promptly delete this e-mail and any attachment
> and all copies and inform the sender.
>
> Please note that any views or opinions presented in this email are solely
> those of the author and do not necessarily represent those of the University
> of the West of Scotland.
>
> As a public body, the University of the West of Scotland may be required to
> make available emails as well as other written forms of information as a
> result of a request made under the Freedom of Information (Scotland) Act 2002.
>
>
