llvm dev - Aug 2007 - [LLVMdev] llvm-gcc4 and setjmp

Hi Anton,
> > I would expect llvm-gcc to use LLVM's setjmp/longjmp intrinsics
and
> > then to run the LowerSetJmp pass to turn the intrinsic calls into uses
> > of invoke and unwind. At that point, the control flow is explicit,
> > isn't it?
> Unfortunately, no. You can call setjmp/longjmp on the same jump buffer
> multiple times. So, in general it's not possible to determine, where
> jump destination is. The problem is much worse in case, when jump buffer
> escapes from the function, where it was initialized (like in your case -
> longjmp is called in the g() routine).
LowerSetJmp should handle this by turning the call to g() into an invoke. If
g() calls longjmp(), it will do an unwind.

Are you saying that the LowerSetJmp pass doesn't work? Or that the whole
idea of lowering setjmp/longjmp to invoke/unwind doesn't work?

Thanks,
Jay.
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> > Unfortunately, no. You can call setjmp/longjmp on the same jump buffer
> > multiple times. So, in general it's not possible to determine,
where
> > jump destination is. The problem is much worse in case, when jump
buffer
> > escapes from the function, where it was initialized (like in your case
-
> > longjmp is called in the g() routine).
> 
> LowerSetJmp should handle this by turning the call to g() into an invoke.
If
> g() calls longjmp(), it will do an unwind.
> 
> Are you saying that the LowerSetJmp pass doesn't work? Or that the
whole
> idea of lowering setjmp/longjmp to invoke/unwind doesn't work?
If setjmp/longjmp are turned into invoke + unwind, how does this interact
with exception handling codegen (-enable-eh)?  Won't eh codegen break this
trick?

Ciao,

Duncan.

Hi,

is there documentation about what happens to setjmp() et al, and how one 
should handle the setjmp intrinsics? Are setjmp() function calls transformed 
to intrinsics, or are the intrinsics only used for EH?

Thanks,
Torvald