https://issues.dlang.org/show_bug.cgi?id=18573

Matthew Gamble <gamblemj@gmail.com> changed:

           What    |Removed                     |Added
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           Severity|enhancement                 |normal

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https://issues.dlang.org/show_bug.cgi?id=18573

Ketmar Dark <ketmar@ketmar.no-ip.org> changed:

           What    |Removed                     |Added
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                 CC|                            |ketmar@ketmar.no-ip.org

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https://issues.dlang.org/show_bug.cgi?id=18573

--- Comment #1 from Ketmar Dark <ketmar@ketmar.no-ip.org> ---
some clarification: basically, this boils down to codegen bug: if we have function that returns some floating point value, and FPU is involved, and caller does `cast(void)myfunc()`, result is not popped from FPU stack.

note that `cast(void)` is vital here: everything is ok without it. also, as X86_64 doesn't use FPU for floats and doubled, you need to use `real` there to trigger the bug.

minified sample by ag0aep6g:

double f() { return 1; }
void main()
{
    cast(void) f();
    cast(void) f();
    cast(void) f();
    cast(void) f();
    cast(void) f();
    cast(void) f();
    cast(void) f();

    double b = 2;
    assert(b == 2); /* fails; should pass */
}

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https://issues.dlang.org/show_bug.cgi?id=18573

Ketmar Dark <ketmar@ketmar.no-ip.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|phobos                      |dmd
           Hardware|x86                         |All
                 OS|Windows                     |All

--- Comment #2 from Ketmar Dark <ketmar@ketmar.no-ip.org> ---
p.s.: as this bug affects x86_64 too (albeit only with `real`s), i changed arch
to all.

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https://issues.dlang.org/show_bug.cgi?id=18573

Steven Schveighoffer <schveiguy@yahoo.com> changed:

           What    |Removed                     |Added
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                 CC|                            |schveiguy@yahoo.com

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https://issues.dlang.org/show_bug.cgi?id=18573

ag0aep6g@gmail.com changed:

           What    |Removed                     |Added
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           Keywords|                            |wrong-code
                 CC|                            |ag0aep6g@gmail.com

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https://issues.dlang.org/show_bug.cgi?id=18573

ag0aep6g@gmail.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|std.algorithm each does not |`cast(void)` leads to
                   |function correctly for      |floating point return value
                   |assignment under x86        |not being popped from FPU
                   |                            |stack

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https://issues.dlang.org/show_bug.cgi?id=18573

ag0aep6g <ag0aep6g@gmail.com> changed:

           What    |Removed                     |Added
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                 CC|                            |dkorpel@live.nl

--- Comment #3 from ag0aep6g <ag0aep6g@gmail.com> ---
*** Issue 19437 has been marked as a duplicate of this issue. ***

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https://issues.dlang.org/show_bug.cgi?id=18573

Walter Bright <bugzilla@digitalmars.com> changed:

           What    |Removed                     |Added
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                 CC|                            |bugzilla@digitalmars.com

--- Comment #4 from Walter Bright <bugzilla@digitalmars.com> ---
The test case:

  real foo();

  void test1() {
    cast(void)foo();
  }

  void test2() {
    foo();
  }

compiles to:

  __D4test5test1FZv:
             call    __D4test3fooFZe
             ret

  __D4test5test2FZv:
             call    __D4test3fooFZe
             fstp    ST
             ret

which nicely illustrates the problem.

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https://issues.dlang.org/show_bug.cgi?id=18573

Walter Bright <bugzilla@digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|`cast(void)` leads to       |cast(void) leads to
                   |floating point return value |floating point return value
                   |not being popped from FPU   |not being popped from FPU
                   |stack                       |stack

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