[Bug libstdc++/65630] [5 Regression] operator+ for new std::string not exported

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65630

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Strictly nothing says it has to, but it works with the old std::string, because
we do export those functions from libstdc++.so

We also instantiate them for the new string, I just didn't add exports for them
to the linker script.

We could stop instantiating them and say it's no longer supported, but it seems
better to just add the export:


--- a/libstdc++-v3/config/abi/pre/gnu.ver
+++ b/libstdc++-v3/config/abi/pre/gnu.ver
@@ -1675,6 +1675,9 @@ GLIBCXX_3.4.21 {
     _ZNSt7__cxx1112basic_string*;
     _ZNKSt7__cxx1112basic_string*;

+    # Concatenation operators for ABI-tagged std::basic_string
+   
_ZStplI[cw]St11char_traitsI[cw]ESaI[cw]EENSt7__cxx1112basic_stringIT_T0_T1_EE*;
+
     # ABI-tagged stringstreams
     _ZNSt7__cxx1115basic_stringbuf*;
     _ZNSt7__cxx1118basic_stringstream*;