On 07/01/2024 17:34, Jonathan Wakely wrote:
On Sun, 7 Jan 2024 at 12:57, François Dumont <frs.dum...@gmail.com> wrote:
Hi
While working on the patch to use the cxx11 abi in gnu version namespace
mode I got a small problem with this missing constructor. I'm not sure
that the main patch will be integrated in gcc 14 so I think it is better
if I propose this patch independently.
libstdc++: Add __cow_string constructor from C string
The __cow_string is instantiated from a C string in
cow-stdexcept.cc. At the moment
the constructor from std::string is being used with the drawback of
an intermediate
potential allocation/deallocation and copy. With the C string
constructor we bypass
all those operations.
But in that file, the std::string is the COW string, which means that
when we construct a std::string and copy it, it's cheap. It's just a
reference count increment/decrement. There should be no additional
allocation or deallocation.
Good remark but AFAI understand in this case std::string is the cxx11
one. I'll take a second look.
Clearly in my gnu version namespace patch it is the cxx11 implementation.
Even if so, why do we want to do those additional operations ? Adding
this C string constructor will make sure that no useless operations will
be done.
Am I missing something?
libstdc++-v3/ChangeLog:
* include/std/stdexcept (__cow_string(const char*)): New
definition.
* src/c++11/cow-stdexcept.cc (__cow_string(const char*)):
New definition and
declaration.
Tested under Linux x64, ok to commit ?
François
