[cfe-dev] What makes Clang non-deterministic?

[Sean Silva]

On Thu, Jan 1, 2015 at 8:44 AM, Mikael Persson <mikael.s.persson at gmail.com>
wrote:

> Hi,
>
> I've been chasing some bugs in templight (template instantiation profiler)
> by generating traces for some template-heavy code, and in the process, I've
> been printing out some debug information including the total number of
> template instantiations that clang does when compiling the source code.
> From multiple runs in succession (with same clang binary and same source
> file), there is always a small fluctuation in the number of instantiations
> done, by roughly 1% - 2% (for example, one of my source files yields total
> instantiation counts that fluctuate between 203,000 and 208,000).
>

Can you diff the traces?

-- Sean Silva


>
> So, Clang is non-deterministic (at least, at semantic analysis). I'm just
> curious as to why that is? Is it some special technique being used? Or is
> it the consequence of some UB bugs?
>
> Cheers,
> Mikael.
>
> --
> Sven Mikael Persson, M.Sc.(Tech.)
>
>
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