[LLVMdev] Getting exceptions to work?

[Nicolas Geoffray]

Hi Talin,

You're not using the llvm intrinsics for exception handling, so your 
code won't work. Using _Unwind_RaiseException should be OK, but your 
main function must at least use llvm.eh.exception, 
llvm.eh.selector.i32/64 and probably __cxa_begin_catch and __cxa_end_catch.

Nicolas


Talin wrote:
> I've been struggling for several days, trying to get native exceptions 
> to work in my code. I managed to boil down the IR to the simplest 
> possible example that I can think of.
>
> If anyone on this list can tell me what changes I need to make to the 
> following code to get it to work (i.e. return 0 instead of a bus 
> error), it would make my life immensely better.
>
>    ; ModuleID = 'ExceptionTest'
>        %Object = type {}
>        %UnwindInfo = type { i64, void (i32, %UnwindInfo *)*, i16, i16 }
>        %Throwable = type { %Object, %UnwindInfo }
>
>    define i32 @main(i32, i8**) nounwind {
>    entry:
>        invoke fastcc void @throwSomething() to label %nounwind unwind
>    label %catch
>
>    catch:
>        ret i32 0
>
>    nounwind:
>        ret i32 -1
>    }
>
>    define internal fastcc void @throwSomething() noreturn {
>    entry:
>        %throwable = malloc %Throwable
>        call fastcc void @Throwable.construct(%Throwable* %throwable)
>        %unwindInfo = getelementptr %Throwable* %throwable, i32 0, i32 1
>        %throw = call i32 @_Unwind_RaiseException(%UnwindInfo* 
> %unwindInfo)
>        unreachable
>    }
>
>    define internal fastcc void @Throwable.construct(%Throwable* %self)
>    nounwind {
>    entry:
>        %exceptionClass = getelementptr %Throwable* %self, i32 0, i32 1,
>    i32 0
>        store i64 0, i64* %exceptionClass
>        %exceptionCleanup = getelementptr %Throwable* %self, i32 0, i32
>    1, i32 1
>        store void (i32, %UnwindInfo *)* @exceptionCleanupFn, void (i32,
>    %UnwindInfo *)** %exceptionCleanup
>        %private1 = getelementptr %Throwable* %self, i32 0, i32 1, i32 2
>        store i16 0, i16* %private1
>        %private2 = getelementptr %Throwable* %self, i32 0, i32 1, i32 3
>        store i16 0, i16* %private2
>        ret void
>    }
>
>    define internal void @exceptionCleanupFn(i32 %reason, %UnwindInfo *
>    %exc) {
>      ret void
>    }
>
>    declare i32 @_Unwind_RaiseException(%UnwindInfo*) noreturn
>
> -- Talin
>
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>
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