[llvm-bugs] [Bug 36750] Meyers' singleton does not work with [[gnu::pure]] and -O1 to -O3

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=36750

Eli Friedman <efriedma at codeaurora.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |INVALID
             Status|REOPENED                    |RESOLVED

--- Comment #5 from Eli Friedman <efriedma at codeaurora.org> ---
That's still wrong; the function writes to memory.

The point the gcc developer is making is that *if you can hide the
initialization from the compiler* then the function is "pure" because the
compiler can't prove when the initialization actually happened, so you can
pretend the function never had any side-effects in the first place.  Here, the
compiler can see the initialization, so that reasoning doesn't work.

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