[Bug c/61689] New: Assignment and Operator not working as intended.

[Bug c/61689] New: Assignment and Operator not working as intended.

[wmichaelv at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61689

            Bug ID: 61689
           Summary: Assignment and Operator not working as intended.
           Product: gcc
           Version: 4.7.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: wmichaelv at hotmail dot com

Created attachment 33063
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33063&action=edit
c code

iR = -iX * iR + iZ / iY * iA / (iA = iR = iC / iB);

Couldn't detect the source of error.
The output is displayed correctly in visual studio 2008, but not in gcc.

complete code is attached.

[Bug c/61689] Assignment and Operator not working as intended.

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61689

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
                 CC|                            |mpolacek at gcc dot gnu.org
         Resolution|---                         |INVALID

--- Comment #1 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
The program has undefined behaviour; an assignment is not a sequence point. 
See what -Wsequence-point says.

[Bug c/61689] Assignment and Operator not working as intended.

[manu at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61689

Manuel López-Ibáñez <manu at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |manu at gcc dot gnu.org

--- Comment #3 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
(In reply to wmichaelv from comment #2)
> (In reply to Marek Polacek from comment #1)
> > The program has undefined behaviour; an assignment is not a sequence point. 
> > See what -Wsequence-point says.
> 
> According to the order operation, grouping should be calculated first before
> add, subtract, division, and multiplication, and assignment. And the
> associativity of assignment is from right to left.

Where in the standard does it say so?

http://stackoverflow.com/questions/22817517/do-parentheses-force-order-of-evaluation-and-make-an-undefined-expression-define

Clang also believes this code is broken (it looks broken to me):

test.c:13:37: warning: unsequenced modification and access to 'iA'
[-Wunsequenced]
        iR = -iX * iR + iZ / iY * iA / (iA = iR = iC / iB);
                                  ~~       ^
test.c:13:42: warning: unsequenced modification and access to 'iR'
[-Wunsequenced]
        iR = -iX * iR + iZ / iY * iA / (iA = iR = iC / iB);
                   ~~                           ^
2 warnings generated.
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61628

Kai Tietz <ktietz at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |ktietz at gcc dot gnu.org

--- Comment #19 from Kai Tietz <ktietz at gcc dot gnu.org> ---
I tested sample in comment #14 with mingw-w64 on 32-bit and 64-bit.

My results are for 64-bit:

On compile already the error-message: 'Schwerwiegender Fehler: Feldelementgröße
bei (1) zu groß'

Interestingly on 32-bit compile works and on execution the word 'begin' is
written. Afterwards process terminates normal in gdb.
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From: "wmichaelv at hotmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/61689] Assignment and Operator not working as intended.
Date: Thu, 03 Jul 2014 16:18:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?ida689

--- Comment #4 from wmichaelv at hotmail dot com ---
Ah, thank you. That clears it up. And my apology for my ignorant.