http://llvm.org/bugs/show_bug.cgi?id=16298
Bug ID: 16298
Summary: llvm.eh.unwind.init() is mostly a no-op, which subtly
breaks libgcc_eh
Product: tools
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: llc
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
If libgcc_eh is built with Clang + LLVM, it is subtly broken, because
__builtin_unwind_init() is compiled to the llvm.eh.unwind.init() intrinsic,
which is largely a no-op.
__builtin_unwind_init() is supposed to cause the function's prologue and
epilogue to save and restore all registers, but llvm.eh.unwind.init() doesn't
have this effect. _Unwind_RaiseException(), _Unwind_Resume() etc. use other
GCC builtins to get the address of the register save area and modify the saved
register values, before calling __builtin_eh_return() to return and modify the
stack pointer at the same time.
This means that when libgcc_eh is compiled with LLVM, _Unwind_RaiseException(),
_Unwind_Resume() etc. won't necessarily restore all registers properly when
unwinding the stack to handle a C++ exception. If they work, it's by luck.
It would be better if __builtin_unwind_init() were rejected at compile time,
rather than being accepted but not having the intended effect.
See also this PNaCl bug:
https://code.google.com/p/nativeclient/issues/detail?id=3486
--
You are receiving this mail because:
You are on the CC list for the bug.
_______________________________________________
LLVMbugs mailing list
[email protected]
http://lists.cs.uiuc.edu/mailman/listinfo/llvmbugs
