[LLVMbugs] [Bug 22270] New: libunwind: fallback implementation of _dyld_find_unwind_sections fails to build for __LP64__ and crashes during exception throwing

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=22270

            Bug ID: 22270
           Summary: libunwind: fallback implementation of
                    _dyld_find_unwind_sections fails to build for __LP64__
                    and crashes during exception throwing
           Product: libc++abi
           Version: unspecified
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: All Bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: jeremyhu at apple.com
                CC: llvmbugs at cs.uiuc.edu, mclow.lists at gmail.com
    Classification: Unclassified

Created attachment 13710
  --> http://llvm.org/bugs/attachment.cgi?id=13710&action=edit
test_throw.cxx

A simple exception throw in C++ will cause a crash on Leopard.  Similar results
are observed if building libunwind.dylib on Syrah and forcing it to use the
fallback implementation of _dyld_find_unwind_sections.

$ git clone https://github.com/jeremyhu/libcxxabi.git
$ cd libcxxabi/src/Unwind
$ git checkout debug-dyld_find_unwind_sections
$ make LIBDIR=/usr/lib/system LIBUNWIND_FILENAME=libunwind.dylib CFLAGS="-g3
-O0" CXXFLAGS="-g3 -O0"
...

$ clang++ -arch x86_64 test_throw.cxx -o test_throw.x86_64
$ DYLD_LIBRARY_PATH=. ./test_throw.x86_64
Segmentation fault: 11

$ clang++ -arch i386 test_throw.cxx -o test_throw.i386
$ DYLD_LIBRARY_PATH=. ./test_throw.i386
Segmentation fault: 11

---

Thread 0 Crashed:: Dispatch queue: com.apple.main-thread
0   libmacho.dylib                    0x9335236c getsectiondata + 49
1   libunwind.dylib                   0x000f4932
libunwind::_dyld_find_unwind_sections(void*, libunwind::dyld_unwind_sections*)
+ 114 (.AddressSpace.hpp:317)
2   libunwind.dylib                   0x000f5a4b
libunwind::LocalAddressSpace::findUnwindSections(unsigned int,
libunwind::UnwindInfoSections&) + 43 (.AddressSpace.hpp:337)
3   libunwind.dylib                   0x000f54b2
libunwind::UnwindCursor<libunwind::LocalAddressSpace,
libunwind::Registers_x86>::setInfoBasedOnIPRegister(bool) + 114
(.UnwindCursor.hpp:1158)
4   libunwind.dylib                   0x000f3ef0 unw_init_local + 176
(libunwind.cpp:63)
5   libunwind.dylib                   0x000f057d unwind_phase1 + 77
(UnwindLevel1.c:34)
6   libunwind.dylib                   0x000f04dd _Unwind_RaiseException + 157
(UnwindLevel1.c:343)
7   libc++abi.dylib                   0x98e794c8 __cxa_throw + 103
8   test_throw.i386                   0x000eae2a main + 90
9   libdyld.dylib                     0x90c546d9 start + 1

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