[PATCH v4] libstdc++: Use allocate_at_least in vector, string (P0401) [PR118030]

[Jonathan Wakely]

On Tue, 26 May 2026 at 08:04, Stephan Bergmann <sberg.fun@gmail.com> wrote:
>
> On 5/26/26 07:44, Nathan Myers wrote:
> > On 5/26/26 1:35 AM, Stephan Bergmann wrote:
> >> At least with clang-22.1.5-1.fc44.x86_64 and with recent Clang 23
> >> trunk, this started to fail
> >>
> >>> $ cat test.cc
> >>> #include <string>
> >>> int main(int argc, char **) {
> >>>   char buf[32] = {};
> >>>   return std::string(buf, buf + argc + 20).size();
> >>> }
> >>
> >>> $ clang++ --gcc-install-dir=/home/sberg/gcc/inst/lib/gcc/x86_64-pc-
> >>> linux-gnu/17.0.0 -O1 test.cc
> >>> /usr/bin/ld.bfd: /tmp/test-caae58.o: in function `main':
> >>> test.cc:(.text+0x32): undefined reference to
> >>> `std::__cxx11::basic_string<char, std::char_traits<char>,
> >>> std::allocator<char> >::_M_create_plus(unsigned long, unsigned long)'
> >>> clang++: error: linker command failed with exit code 1 (use -v to see
> >>> invocation)
> >
> > Thank you.
> >
> > Is your version of Clang picking up symbols declared in section
> > GLIBCXX_3.4.36 of config/abi/pre/gnu.ver ? Using libstdc++.so
> > built with the object linked in?
> >
> > That section is targetted at unreleased GCC 17.
>
> Oh, sorry, my bad:  This was an incremental build of GCC.  With a
> from-scratch one, everything's fine again!

We don't have makefile dependencies for the .o files in libstdc++ so
if the basic_string.{h,tcc} files change, we don't rebuild
string-inst.o etc.