http://d.puremagic.com/issues/show_bug.cgi?id=3667

           Summary: broken out(result) in contracts
           Product: D
           Version: 2.038
          Platform: Other
        OS/Version: All
            Status: NEW
          Severity: regression
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: netrino@inbox.ru


--- Comment #0 from Ludwig <netrino@inbox.ru> 2010-01-03 11:33:25 PST ---
Regression bug since 2.037. For example in such code:

import std.stdio;

int mul100(int n)
out(result)
{
    writeln("result == ", result);
}
body
{
    return n * 100;
}

int main()
{
    mul100(5);
    return 0;
}

compiled with -debug output is always
result == 0 and should be result == 500

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Luther Tychonievich <lat7h@virginia.edu> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |lat7h@virginia.edu


--- Comment #1 from Luther Tychonievich <lat7h@virginia.edu> 2010-01-12 13:09:11 PST ---
More details: for any primitive type (all integer, character, and floating point types, including unsigned, complex, and typedef'd varieties thereof) the out contract's result will always be type.init.  For example, the following code works (and shouldn't, the out contract is incorrect):
-------
typedef cdouble sometype = 4.0 + 2.0i;

sometype buggy()
  out(result) { assert( result == 4.0 + 2.0i ); } // should fail but doesn't
  body        { return cast(sometype)0;  }

unittest { assert(buggy() == 0); }
-------

This does not happen for structs, classes, static or dynamic arrays (all seem
to function correctly).

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Andrei Alexandrescu <andrei@metalanguage.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |andrei@metalanguage.com


--- Comment #2 from Andrei Alexandrescu <andrei@metalanguage.com> 2010-02-21 17:01:52 PST ---
An example involving a nested function:

void fun() {
    int gun()
        out(result)
    {
        assert(result == 42);
    } body
    {
        return 42;
    }

    gun();
}

void main() {
    fun();
}

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Witold Baryluk <baryluk@smp.if.uj.edu.pl> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |baryluk@smp.if.uj.edu.pl


--- Comment #3 from Witold Baryluk <baryluk@smp.if.uj.edu.pl> 2010-03-09 17:08:03 PST ---
It is probably related to bug3634

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Don <clugdbug@yahoo.com.au> changed:

           What    |Removed                     |Added
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                 CC|                            |bearophile_hugs@eml.cc


--- Comment #4 from Don <clugdbug@yahoo.com.au> 2010-03-15 00:55:50 PDT ---
*** Issue 3963 has been marked as a duplicate of this issue. ***

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--- Comment #5 from Luther Tychonievich <lat7h@virginia.edu> 2010-03-15 20:43:30 PDT ---
Not sure if it helps, but the compiler knows this problem will arise at compile time; the following compiles just fine, though it clearly should not:
-----
int buggy(int y)
out(result) { static assert(result==0); }
body        { return y; }
void main() { buggy(3); }
----
I don't know why.  Debugging shows that statement.c:3490 still creates the "result = y" assignment I'd expect... I don't know where else to look.

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--- Comment #6 from Shin Fujishiro <rsinfu@gmail.com> 2010-05-07 11:30:35 PDT ---
Created an attachment (id=624)
Patch for DMD 2.045

The attached patch should fix the problem.

Since DMD 2.028, result variables are marked as const.  The cause of this bug is that DMD mistakenly tries to const-fold a result variable into its default initializer.  Unfortunately, it succeeds when return type is a basic value type (int, bool, etc.).

The attached patch adds a STCresult storage class to declaration.h, and applies it to the vresult.  The STCresult is similar to the STCparameter; it disables default-value initialization of result variables.

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Walter Bright <bugzilla@digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |bugzilla@digitalmars.com
         Resolution|                            |FIXED


--- Comment #7 from Walter Bright <bugzilla@digitalmars.com> 2010-05-15 16:17:46 PDT ---
changelog 490

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--- Comment #8 from Don <clugdbug@yahoo.com.au> 2010-06-07 00:11:57 PDT ---
*** Issue 3634 has been marked as a duplicate of this issue. ***

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