[Bug lto/62026] [4.9/5 Regression] Crash in lto_get_decl_name_mapping

[trippels at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62026

--- Comment #11 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
Thanks for the testcase.

Reduced:

markus@x4 /tmp % cat ErrorTry.ii
template <typename T>
class B {
 public:
  T values;
  T operator[](int);
};
class C;
class D {
 public:
  int m_fn2();
  virtual C *m_fn1();
};
class C : public D {
 public:
  virtual B<int> *m_fn3(int);
};
class F : D, C {
  B<int> *offsets;
  B<int> *m_fn3(int);
};
B<int> *F::m_fn3(int) {
  if (offsets) return 0;
}
void fn1(B<D *> &p1) {
  for (int i;;) {
    C *a = p1[0]->m_fn1();
    a->m_fn2() && a->m_fn3(0);
  }
}
markus@x4 /tmp % g++ -flto -O3 -r -nostdlib ErrorTry.ii
ErrorTry.ii:17:7: warning: direct base ‘D’ inaccessible in ‘F’ due to ambiguity
 class F : D, C {
       ^
lto1: internal compiler error: Segmentation fault
0x943f9f crash_signal
        ../../gcc/gcc/toplev.c:340
0x843af8 lto_get_decl_name_mapping(lto_file_decl_data*, char const*)
        ../../gcc/gcc/lto-section-in.c:340
0x83ce96 copy_function_or_variable
        ../../gcc/gcc/lto-streamer-out.c:2163
0x83dae1 lto_output()
        ../../gcc/gcc/lto-streamer-out.c:2255
0x889701 write_lto
        ../../gcc/gcc/passes.c:2228
0x88cccb ipa_write_optimization_summaries(lto_symtab_encoder_d*)
        ../../gcc/gcc/passes.c:2425
0x55db6a do_stream_out
        ../../gcc/gcc/lto/lto.c:2463
0x55f849 stream_out
        ../../gcc/gcc/lto/lto.c:2505
0x55f849 lto_wpa_write_files
        ../../gcc/gcc/lto/lto.c:2642
0x568a94 do_whole_program_analysis
        ../../gcc/gcc/lto/lto.c:3310
0x568a94 lto_main()
        ../../gcc/gcc/lto/lto.c:3430
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