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digitalmars.D.bugs - [Issue 8790] New: Compiling with optimization produces erroneous variable initialization error

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=8790

           Summary: Compiling with optimization produces erroneous
                    variable initialization error
           Product: D
           Version: D2
          Platform: All
        OS/Version: Linux
            Status: NEW
          Severity: regression
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: hsteoh quickfur.ath.cx


--- Comment #0 from hsteoh quickfur.ath.cx 2012-10-09 17:41:02 PDT ---
import std.algorithm;
import std.range;

void main() {
    auto N2 = sequence!"n"(cast(size_t)1).map!"a";
}


When compiling with dmd -O (latest git for dmd, druntime, phobos), this
produces the following errors:

/usr/src/d/phobos/std/range.d(4590): Error: variable upper used before set
/usr/src/d/phobos/std/range.d(4590): Error: variable lower used before set

The referenced line of code occurs in this context:

    auto opSlice(size_t lower, size_t upper)
    in
    {  
        assert(upper >= lower); // this is line 4590
    }
    body
    {  
        auto s = typeof(this)(this._state, this._n + lower);
        return takeExactly(s, upper - lower);
    }

Which makes no sense, because there is nothing wrong with the reference to
upper and lower (they are function parameters). Perhaps the optimizer
inadvertently permuted the order of stuff in a way that caused the contract to
run before the parameters are initialized?

If -O is not specified, the compile is successful. This problem appears to be
independent of whether I specify -m32 or -m64.

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parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=8790


Jonathan M Davis <jmdavisProg gmx.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |jmdavisProg gmx.com
         Resolution|                            |DUPLICATE


--- Comment #1 from Jonathan M Davis <jmdavisProg gmx.com> 2012-10-09 19:22:06
PDT ---
I believe that this is a duplicate of bug# 8556. I suspect that at least part
of the problem is that takeExactly checks hasSlicing, so if you're using
takeExactly to do slicing, it's going to cause problems right now. I'm almost
finished on a pull request which will fix that, and that may or may not make it
so that this bug doesn't manifest itself with sequence, but if anything, that
means that we'd need to find another way to reproduce this bug, because that
will just fix the Phobos part, not the compiler bug.

*** This issue has been marked as a duplicate of issue 8556 ***

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