[libcxx-dev] C++ exception issue on LLVM

[zhangwentao (M) via libcxx-dev]

Hi all,

I am using LLVM C++ in my project. Everything is good except exception. (version 6.0.1 release)

Version:  6.0.1
PLATFORM: arm 32 little endian.
A normal test case for try{}.... Catch(...) test case will crash.  (RTTI, STL test cases work fine.)

Compiler CLANG, with -frtti -fexpceptions options.

Crashed Information:

1.      Crashed in 'scan_eh_tab' function in `src/cxa_personality.cpp `.

715                    const  __shim_type_info* catchType =
716                         get_shim_type_info(static_cast<uint64_t>(ttypeIndex),
717                                           classInfo, ttypeEncoding,
718                                           native_exception, unwind_exception);  // get catchType by calling get_shim_type_info.
......
760                         printf(" => catchType->name()=%s\n", catchType->name()); // visit catchType->name(); don't crash. But the name() is empty, I wonder if there is something wrong with RTTI??
761                         printf("before can catch can catch => excpType=%p, adjustedPtr=%p, catchType=%s\n", excpType, adjustedPtr, typeid(*catchType).name());  // if add a typeid(*catchType).name(), crashed here
762                         if (catchType->can_catch(excpType, adjustedPtr))    /// normally crashed here.. if remove this function call, the exception test could work fine for the basic test case.
763                         {


341 static const  __shim_type_info*
342 get_shim_type_info(uint64_t ttypeIndex, const uint8_t* classInfo,
343                    uint8_t ttypeEncoding, bool native_exception,
344                    _Unwind_Exception* unwind_exception)
345 {
346     if (classInfo == 0)
347     {
348         // this should not happen.  Indicates corrupted eh_table.
349         call_terminate(native_exception, unwind_exception);
350     }
351
352     assert(((ttypeEncoding == DW_EH_PE_absptr) ||  // LLVM or GCC 4.6
353             (ttypeEncoding == DW_EH_PE_pcrel) ||  // GCC 4.7 baremetal
354             (ttypeEncoding == (DW_EH_PE_pcrel | DW_EH_PE_indirect))) &&  // GCC 4.7 linux
355            "Unexpected TTypeEncoding");
356     (void)ttypeEncoding;
357
358     const uint8_t* ttypePtr = classInfo - ttypeIndex * sizeof(uintptr_t);
359     return reinterpret_cast<const __shim_type_info *>(
360         read_target2_value(ttypePtr));
361 }


I do not known c++ exception very well, If I am correct the function get_shim_type_info will get shim_type_info from LSDA in elf section right??

If so, I wonder where the __shim_type_info constructed ?  I guess, forget me if not correct: here just covert a memory in elf to a class ptr, maybe the vtable is not created for the ptr???

Do you have any idea about my case??


Thanks a lot~~
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