[Issue 5749] argument evaluation order of chained function from right

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https://d.puremagic.com/issues/show_bug.cgi?id=5749



--- Comment #9 from github-bugzi...@puremagic.com 2014-01-04 22:27:55 PST ---
Commits pushed to master at https://github.com/D-Programming-Language/dmd

https://github.com/D-Programming-Language/dmd/commit/7a31af4b65667fa6a993743f493e8d5f156e0d30
fix Issue 5749 - argument evaluation order of chained function from right

https://github.com/D-Programming-Language/dmd/commit/d9c783cac6d06b7be8b5888e574694aec426a470
Merge pull request #2881 from 9rnsr/fix5749

Issue 5749 - argument evaluation order of chained function from right

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[Issue 5749] argument evaluation order of chained function from right

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Kenji Hara k.hara...@gmail.com changed:

   What|Removed |Added

   Keywords||pull


--- Comment #6 from Kenji Hara k.hara...@gmail.com 2013-11-25 17:34:28 PST ---
https://github.com/D-Programming-Language/dmd/pull/2881

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[Issue 5749] argument evaluation order of chained function from right

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bearophile_h...@eml.cc changed:

   What|Removed |Added

 CC||bearophile_h...@eml.cc


--- Comment #7 from bearophile_h...@eml.cc 2013-11-25 17:48:47 PST ---
This patch seems important.

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[Issue 5749] argument evaluation order of chained function from right

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Kenji Hara k.hara...@gmail.com changed:

   What|Removed |Added

   Keywords||wrong-code
   Severity|enhancement |major


--- Comment #8 from Kenji Hara k.hara...@gmail.com 2013-11-25 18:28:48 PST ---
(In reply to comment #7)
 This patch seems important.

The root issue is very similar to bug 8396. When method call is used, the side
effect of callable entity (evaluation of 'this' object + getting member
function pointer) is not ordered before the arguments evaluation.

I think this is not intended behavior. For example, this code evaluates
function arguments left-to-right.

extern (C) int printf(const char*, ...);
void main()
{
void delegate(int) foo(int i)
{
printf(i: %d\n, i);
return (a){ foo(a); };
}
auto getFunc() { return foo; }

int i;
getFunc()(++i)(++i);
// getFunc() is evaluated before the first ++i expression,
// and getFunc()(++i) is evaluated before the second ++i expression.
}

Because l-to-r evaluation is enforced by the glue-layer code
https://github.com/D-Programming-Language/dmd/blob/7360ae8611add4dc0a89cd870a6ac6490fb2a19b/src/e2ir.c#L3706

The code was introduce by the commit:
https://github.com/D-Programming-Language/dmd/commit/80e2319878bee3bb139a20c0bc1b85b1ec04b892

If you comment out the part, above example code will be broken.

Therefore, I'll change this issue to 'wrong-code' bug.

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[Issue 5749] argument evaluation order of chained function from right

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d...@dawgfoto.de changed:

   What|Removed |Added

 CC||d...@dawgfoto.de


--- Comment #5 from d...@dawgfoto.de 2011-09-07 15:53:41 PDT ---
The result also changes with respect to enabling -inline or not.

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[Issue 5749] argument evaluation order of chained function from right

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--- Comment #3 from Steven Schveighoffer schvei...@yahoo.com 2011-03-18 
13:37:35 PDT ---
If you consider that 'this' is the first argument to the opCall, you would
expect this to do the same thing:

A blah(A a, size_t i)
{
   printf(i=%d\n, i);
   return a;
}

blah(blah(a, ++i), ++i);

but it does print:

i=1
i=2

So there is something definitely inconsistent here.

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--- Comment #4 from Fawzi Mohamed fa...@gmx.ch 2011-03-18 13:59:28 PDT ---
clearly about this I agree with Steven, the correct (or expected if you
prefer) evaluation should be to evaluate the arguments as late as possible.

a(b)(c); is the same as (a(b))(c) I would expect c not to be evaluated before
a(b) is fully evaluated (both b *and* a(b)), otherwise whisper style is broken,
and is counterintuitive.

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