[PATCH] D86254: [libunwind] Minor fixes in libunwind

[Ryan Prichard via Phabricator via llvm-commits]

rprichard added a comment.

There is a `libunwind::findUnwindSectionsByPhdr` as of 11.x. When I build 11.x libunwind.so for glibc (I tested arm and x86_64), the symbol is exposed:

  $ readelf --dyn-syms unwind-arm/lib/libunwind.so.1.0 | grep findUnwind
      35: 00000f24   204 FUNC    GLOBAL DEFAULT    11 _ZN9libunwind24findUnwindSectionsByPhdrEP12dl_phdr_infojPv
  
  $ readelf --dyn-syms unwind-x86_64/lib/libunwind.so.1.0 | grep findUnwind
      46: 0000000000002c30   854 FUNC    GLOBAL DEFAULT    12 _ZN9libunwind24findUnwindSectionsByPhdrEP12dl_phdr_infomPv

In previous releases, the function was a lambda instead, and the lambda was a hidden symbol (because `LocalAddressSpace` is marked with `_LIBUNWIND_HIDDEN`, which is `__attribute__((visibility("hidden")))`.)

  $ readelf -s unwind-arm/src/CMakeFiles/unwind_shared.dir/libunwind.cpp.o | grep findUnwind
       5: 00000000     0 SECTION LOCAL  DEFAULT    23 .text._ZZN9libunwind17LocalAddressSpace18findUnwindSectionsEjRNS_18UnwindInfoSectionsEENUlP12dl_phdr_infojPvE_4_FUNES4_jS5_
       7: 00000000     0 SECTION LOCAL  DEFAULT    24 .ARM.extab.text._ZZN9libunwind17LocalAddressSpace18findUnwindSectionsEjRNS_18UnwindInfoSectionsEENUlP12dl_phdr_infojPvE_4_FUNES4_jS5_
       8: 00000000     0 SECTION LOCAL  DEFAULT    25 .ARM.exidx.text._ZZN9libunwind17LocalAddressSpace18findUnwindSectionsEjRNS_18UnwindInfoSectionsEENUlP12dl_phdr_infojPvE_4_FUNES4_jS5_
     265: 00000000   204 FUNC    WEAK   HIDDEN     23 _ZZN9libunwind17LocalAddressSpace18findUnwindSectionsEjRNS_18UnwindInfoSectionsEENUlP12dl_phdr_infojPvE_4_FUNES4_jS5_
  
  $ readelf -s unwind-x86_64/src/CMakeFiles/unwind_shared.dir/libunwind.cpp.o | grep findUnwind
      38: 0000000000000000     0 SECTION LOCAL  DEFAULT    80 .text._ZZN9libunwind17LocalAddressSpace18findUnwindSectionsEmRNS_18UnwindInfoSectionsEENUlP12dl_phdr_infomPvE_4_FUNES4_mS5_
     249: 0000000000000000   313 FUNC    WEAK   HIDDEN     80 _ZZN9libunwind17LocalAddressSpace18findUnwindSectionsEmRNS_18UnwindInfoSectionsEENUlP12dl_phdr_infomPvE_4_FUNES4_mS5_

The hidden symbol doesn't make it into the shared object's .dynsym table.

11.0.0-final isn't released yet, so maybe this can be fixed still?

I suspect this function is currently only ever defined in libunwind.cpp.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D86254/new/

https://reviews.llvm.org/D86254