[libcxxabi] r228408 - unwind: use -fno-rtti -fno-exceptions -funwind-tables

[Sergey Dmitrouk]

Hi,

Although code compiles and works in most cases, part of this change (namely
addition of `-fno-exceptions` flag) seems to break exception handling on ARM.
E.g. `catch` doesn't work in this example and `std::terminate()` is invoked:

    int main(void)
    {
        try
        {
            throw 1;
        }
        catch (int)
        {
        }
        return 0;
    }

Is it possible that `-fno-exceptions` makes Clang skip generation of
some auxiliary data, which results in such strange behaviour?

It's not just about `int` type, class types were not caught as well even
with `catch (...)` statement.  In fact almost all tests under
test-suite/SingleSource/Regression/C++/EH failed.

Anyone else seeing this?  libcxxabi is used with LLVM, Clang, compiler-rt
and libcxx here.

Regards,
Sergey

On Fri, Feb 06, 2015 at 09:47:57AM -0800, Saleem Abdulrasool wrote:
> Author: compnerd
> Date: Fri Feb  6 11:47:57 2015
> New Revision: 228408
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=228408&view=rev
> Log:
> unwind: use -fno-rtti -fno-exceptions -funwind-tables
> 
> RTTI and exceptions are not needed for the unwinder, the use of C++ there is for
> very specific cases, and does not require dynamic_cast nor does it use
> exceptions.  This avoids unnecessary references to type information being
> emitted.
> 
> Modified:
>     libcxxabi/trunk/cmake/config-ix.cmake
>     libcxxabi/trunk/src/Unwind/CMakeLists.txt
> 
> Modified: libcxxabi/trunk/cmake/config-ix.cmake
> URL: http://llvm.org/viewvc/llvm-project/libcxxabi/trunk/cmake/config-ix.cmake?rev=228408&r1=228407&r2=228408&view=diff
> ==============================================================================
> --- libcxxabi/trunk/cmake/config-ix.cmake (original)
> +++ libcxxabi/trunk/cmake/config-ix.cmake Fri Feb  6 11:47:57 2015
> @@ -5,6 +5,8 @@ include(CheckCXXCompilerFlag)
>  # Check compiler flags
>  check_c_compiler_flag(-funwind-tables         LIBCXXABI_HAS_FUNWIND_TABLES)
>  check_cxx_compiler_flag(-fPIC                 LIBCXXABI_HAS_FPIC_FLAG)
> +check_cxx_compiler_flag(-fno-exceptions       LIBCXXABI_HAS_NO_EXCEPTIONS_FLAG)
> +check_cxx_compiler_flag(-fno-rtti             LIBCXXABI_HAS_NO_RTTI_FLAG)
>  check_cxx_compiler_flag(-fstrict-aliasing     LIBCXXABI_HAS_FSTRICT_ALIASING_FLAG)
>  check_cxx_compiler_flag(-nodefaultlibs        LIBCXXABI_HAS_NODEFAULTLIBS_FLAG)
>  check_cxx_compiler_flag(-nostdinc++           LIBCXXABI_HAS_NOSTDINCXX_FLAG)
> 
> Modified: libcxxabi/trunk/src/Unwind/CMakeLists.txt
> URL: http://llvm.org/viewvc/llvm-project/libcxxabi/trunk/src/Unwind/CMakeLists.txt?rev=228408&r1=228407&r2=228408&view=diff
> ==============================================================================
> --- libcxxabi/trunk/src/Unwind/CMakeLists.txt (original)
> +++ libcxxabi/trunk/src/Unwind/CMakeLists.txt Fri Feb  6 11:47:57 2015
> @@ -68,6 +68,11 @@ target_link_libraries(unwind ${libraries
>  append_if(LIBCXXABI_COMPILE_FLAGS LIBCXXABI_HAS_FPIC_FLAG -fPIC)
>  append_if(LIBCXXABI_LINK_FLAGS LIBCXXABI_HAS_NODEFAULTLIBS_FLAG -nodefaultlibs)
>  
> +set(LIBUNWIND_COMPILE_FLAGS)
> +append_if(LIBUNWIND_COMPILE_FLAGS LIBCXXABI_HAS_NO_EXCEPTIONS_FLAG -fno-exceptions)
> +append_if(LIBUNWIND_COMPILE_FLAGS LIBCXXABI_HAS_NO_RTTI_FLAG -fno-rtti)
> +append_if(LIBUNWIND_COMPILE_FLAGS LIBCXXABI_HAS_FUNWIND_TABLES -funwind-tables)
> +
>  set(LIBCXXABI_UNWINDER_NAME "unwind")
>  
>  if ( APPLE )
> @@ -86,11 +91,12 @@ if ( APPLE )
>  endif()
>  
>  string(REPLACE ";" " " LIBCXXABI_COMPILE_FLAGS "${LIBCXXABI_COMPILE_FLAGS}")
> +string(REPLACE ";" " " LIBUNWIND_COMPILE_FLAGS "${LIBUNWIND_COMPILE_FLAGS}")
>  string(REPLACE ";" " " LIBCXXABI_LINK_FLAGS "${LIBCXXABI_LINK_FLAGS}")
>  
>  set_target_properties(unwind
>    PROPERTIES
> -    COMPILE_FLAGS "${LIBCXXABI_COMPILE_FLAGS}"
> +    COMPILE_FLAGS "${LIBCXXABI_COMPILE_FLAGS} ${LIBUNWIND_COMPILE_FLAGS}"
>      LINK_FLAGS    "${LIBCXXABI_LINK_FLAGS}"
>      OUTPUT_NAME   "${LIBCXXABI_UNWINDER_NAME}"
>      VERSION       "1.0"
> 
> 
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