[Bug 277236] devel/qt5-script: clang optimization miscompiles qtscript

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=277236

John F. Carr <jfc at mit.edu> changed:

           What    |Removed                     |Added
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                 CC|                            |jfc at mit.edu

--- Comment #2 from John F. Carr <jfc at mit.edu> ---
My first impression is clang is within its rights to break this code.  The JS
implementation tries to store metadata bits in the low bits of a pointer type. 
The compiler is allowed to assume that the low bits of a pointer value are
zero. (Assuming the pointed-to type has alignment rules, which is normally the
case.)  LLVM itself uses a wrapper class instead of an illegal pointer value. 
The wrapper class stores the pointer+tag combination as an integer and provides
a getter method to return an untagged pointer.

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