[Issue 19402] bitshift with long shift amount results in int instead of long

Feb 14, 2019

Feb 15, 2019

https://issues.dlang.org/show_bug.cgi?id=19402 Basile-z <b2.temp@gmx.com> changed: What |Removed |Added ---------------------------------------------------------------------------- Keywords| |pull CC| |b2.temp@gmx.com Hardware|x86 |All OS|Windows |All --- Comment #1 from Basile-z <b2.temp@gmx.com> --- There are changes required in phobos to apply the spec correctly. Maybe even a deprecation required (in which case i would pass my way). Attempt for now: https://github.com/dlang/dmd/pull/9361 --

February 15, 2019

[Issue 19402] bitshift with long shift amount results in int instead of long

Posted by Walter Bright

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Walter Bright

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https://issues.dlang.org/show_bug.cgi?id=19402

Walter Bright <bugzilla@digitalmars.com> changed:

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

--- Comment #2 from Walter Bright <bugzilla@digitalmars.com> ---
The spec is simply wrong. We need to follow the C conventions here, otherwise people will get nasty unexpected bugs. The C90 rule is:

"The integer promotions are performed on each of the operands. The type of the result is that of the promoted left operand. If the value of the right operand is negative or is greater than or equal to the width of the promoted left operand, the behavior is undefined."

C++98 is pretty much the same:

"The operands shall be of integral or enumeration type and integral promotions are performed.  The type of the result is that of the promoted left operand. The behavior is undefined if the right operand is negative, or greater than or equal to the length in bits of the promoted left operand."

The D behavior is:

        exp.e1 = integralPromotions(exp.e1, sc);
        if (exp.e2.type.toBasetype().ty != Tvector)
            exp.e2 = exp.e2.castTo(sc, Type.tshiftcnt);

which matches the C/C++ behavior. The compiler is right, the spec is wrong.

--

https://issues.dlang.org/show_bug.cgi?id=19402 Dlang Bot <dlang-bot@dlang.rocks> changed: What |Removed |Added ---------------------------------------------------------------------------- Keywords| |pull --- Comment #4 from Dlang Bot <dlang-bot@dlang.rocks> --- @dkorpel created dlang/dlang.org pull request #2682 "fix Issue 19402 - specs for promotion rule of shift exp is wrong (without anything else)" fixing this issue: - fix Issue 19402 - specs for promotion rule of shift exp is wrong https://github.com/dlang/dlang.org/pull/2682 --

https://issues.dlang.org/show_bug.cgi?id=19402 Dlang Bot <dlang-bot@dlang.rocks> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |RESOLVED Resolution|--- |FIXED --- Comment #5 from Dlang Bot <dlang-bot@dlang.rocks> --- dlang/dlang.org pull request #2682 "fix Issue 19402 - specs for promotion rule of shift exp is wrong (without anything else)" was merged into master: - 67cd903107782b3f9055d40aca61854b590d9482 by dkorpel: fix Issue 19402 - specs for promotion rule of shift exp is wrong https://github.com/dlang/dlang.org/pull/2682 --

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