[Bug c/59755] New: BUG Increment Operator with Accessing Arrays

[Bug c/59755] New: BUG Increment Operator with Accessing Arrays

[octo.nebula at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59755

            Bug ID: 59755
           Summary: BUG Increment Operator with Accessing Arrays
           Product: gcc
           Version: 4.8.2
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: octo.nebula at gmail dot com

Guys,

The increment operator is not working right. The post ++ should increment value
of the index after the array expression. But in this case, it acts like the pre
++ version.

See code below:

#include <stdio.h>

int main()
{
    int A[2][2] = { { 5, 7}, {9, 10} };

    int m = 0, B[] = { 0, 0 };
    int C = 0, D = 0;

    C = A[m][B[m]];
    D = A[m][B[m++]];

    if  (C != D) {
      fprintf (stderr, "Error: C /= D\n");
      return 1;
    }

     return 0;
}


[sunny@localhost trash]$ gcc test.c
[sunny@localhost trash]$ ./a.out
Error: C /= D
[sunny@localhost trash]$ 


GCC version is 4.8.2

[Bug c/59755] BUG Increment Operator with Accessing Arrays

[octo.nebula at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59755

Arjun <octo.nebula at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |octo.nebula at gmail dot com

--- Comment #1 from Arjun <octo.nebula at gmail dot com> ---
In the example given above, C = 5 which is A[0][0] and D = 9 which is A[1][0].

[Bug c/59755] BUG Increment Operator with Accessing Arrays

[octo.nebula at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59755

Arjun <octo.nebula at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|INVALID                     |WONTFIX

--- Comment #3 from Arjun <octo.nebula at gmail dot com> ---
Why is that so?

Shouldn't the value of m increment after the array indexing? Could you please
explain?

[Bug c/59755] BUG Increment Operator with Accessing Arrays

[trippels at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59755

--- Comment #4 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
Please read the section on -Wsequence-point:
http://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html

[Bug c/59755] BUG Increment Operator with Accessing Arrays

[mpolacek at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59755

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mpolacek at gcc dot gnu.org
         Resolution|WONTFIX                     |INVALID