[mercury-users] Re: segfault in hlc.gc when optimise-constructor-last-call is enabled

[Julien Fischer]

HI Michael,

On Sun, 27 Feb 2011, Michael Day wrote:

> If the attached bad.m is compiled with rotd-2011-02-21 in hlc.gc with 
> optimise-constructor-last-call enabled like this:
>
> mmc --grade hlc.gc --make bad --optimise-constructor-last-call
>
> Then the resulting executable will segfault:
>
> $ ./bad
> num_float(
> *** Mercury runtime: caught segmentation violation ***
> cause: address not mapped to object
> address involved: (nil)

That's not so good :-(

> Any assistance would be very gratefully appreciated, as we do take a 
> performance hit if we have to disable this optimisation.

As a workaround try disabling the removal of excess assignment
unifications, e.g. compile with --no-excess-assign.  Doing so avoids
the problem, at least for the test case.

We will look into the problem.

Cheers,
Julien.
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