[Bug c++/112815] New: ICE: in vague_linkage_p, at cp/decl2.cc:2329 with -flto -fno-weak

["zsojka at seznam dot cz" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112815

            Bug ID: 112815
           Summary: ICE: in vague_linkage_p, at cp/decl2.cc:2329 with
                    -flto -fno-weak
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zsojka at seznam dot cz
  Target Milestone: ---
              Host: x86_64-pc-linux-gnu
            Target: x86_64-pc-linux-gnu

Created attachment 56759
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=56759&action=edit
reduced testcase

This crashes at the same place as PR107990, but with a different backtrace. It
has common -fno-weak flag.

The original testcase didn't output the warning: 'T::T()::U::U()' used but
never defined

Compiler output:
$ x86_64-pc-linux-gnu-gcc -flto -fno-weak testcase.C
testcase.C:7:7: warning: 'T::T()::U::U()' used but never defined
    7 |       U ();
      |       ^
during IPA pass: *free_lang_data
testcase.C:5:12: internal compiler error: in vague_linkage_p, at
cp/decl2.cc:2329
    5 |     struct U
      |            ^
0x74d356 vague_linkage_p(tree_node*)
        /repo/gcc-trunk/gcc/cp/decl2.cc:2329
0x11394bf no_linkage_check(tree_node*, bool)
        /repo/gcc-trunk/gcc/cp/tree.cc:3022
0xfd1cf3 mangle_decl(tree_node*)
        /repo/gcc-trunk/gcc/cp/mangle.cc:4146
0x1ad0a8d decl_assembler_name(tree_node*)
        /repo/gcc-trunk/gcc/tree.cc:719
0x1af7747 assign_assembler_name_if_needed(tree_node*)
        /repo/gcc-trunk/gcc/tree.cc:834
0x2916760 free_lang_data_in_cgraph
        /repo/gcc-trunk/gcc/ipa-free-lang-data.cc:1064
0x2916760 free_lang_data
        /repo/gcc-trunk/gcc/ipa-free-lang-data.cc:1109
0x2916760 execute
        /repo/gcc-trunk/gcc/ipa-free-lang-data.cc:1176
Please submit a full bug report, with preprocessed source (by using
-freport-bug).
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.

$ x86_64-pc-linux-gnu-gcc -v
Using built-in specs.
COLLECT_GCC=/repo/gcc-trunk/binary-latest-amd64/bin/x86_64-pc-linux-gnu-gcc
COLLECT_LTO_WRAPPER=/repo/gcc-trunk/binary-trunk-r14-6051-20231201105652-gb1fe98dee21-checking-yes-rtl-df-extra-nobootstrap-amd64/bin/../libexec/gcc/x86_64-pc-linux-gnu/14.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /repo/gcc-trunk//configure --enable-languages=c,c++
--enable-valgrind-annotations --disable-nls --enable-checking=yes,rtl,df,extra
--disable-bootstrap --with-cloog --with-ppl --with-isl
--build=x86_64-pc-linux-gnu --host=x86_64-pc-linux-gnu
--target=x86_64-pc-linux-gnu --with-ld=/usr/bin/x86_64-pc-linux-gnu-ld
--with-as=/usr/bin/x86_64-pc-linux-gnu-as --disable-libstdcxx-pch
--prefix=/repo/gcc-trunk//binary-trunk-r14-6051-20231201105652-gb1fe98dee21-checking-yes-rtl-df-extra-nobootstrap-amd64
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 14.0.0 20231201 (experimental) (GCC)