[Bug c/33192] New: __imag operator drops side effects in subexpr

[Bug c/33192] New: __imag operator drops side effects in subexpr

[sabre at nondot dot org]

GCC miscompiles this:

int bar();
void foo() {
  int X = __imag bar();
}

to not call bar.

-Chris


-- 
           Summary: __imag operator drops side effects in subexpr
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: sabre at nondot dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33192

Re: [Bug c/33192] New: __imag operator drops side effects in subexpr

[Andrew Pinski]

On 26 Aug 2007 05:21:22 -0000, sabre at nondot dot org
<gcc-bugzilla@gcc.gnu.org> wrote:
> to not call bar.

The problem is in c-typeck.c (build_unary_op) (around line 2986).
the code looks like:
      if (TREE_CODE (arg) == COMPLEX_CST)
        return TREE_IMAGPART (arg);
      else if (TREE_CODE (TREE_TYPE (arg)) == COMPLEX_TYPE)
        return fold_build1 (IMAGPART_EXPR, TREE_TYPE (TREE_TYPE (arg)), arg);
      else
        return convert (TREE_TYPE (arg), integer_zero_node);


So there is no check for TREE_SIDE_EFFECTS.  Maybe it should use
omit_one_operand or build a COMPOUND_EXPR.  Either one will fix the
bug.

-- Pinski

[Bug c/33192] __imag operator drops side effects in subexpr

[pinskia at gmail dot com]

------- Comment #1 from pinskia at gmail dot com  2007-08-26 09:00 -------
Subject: Re:  New: __imag operator drops side effects in subexpr

On 26 Aug 2007 05:21:22 -0000, sabre at nondot dot org
<gcc-bugzilla@gcc.gnu.org> wrote:
> to not call bar.

The problem is in c-typeck.c (build_unary_op) (around line 2986).
the code looks like:
      if (TREE_CODE (arg) == COMPLEX_CST)
        return TREE_IMAGPART (arg);
      else if (TREE_CODE (TREE_TYPE (arg)) == COMPLEX_TYPE)
        return fold_build1 (IMAGPART_EXPR, TREE_TYPE (TREE_TYPE (arg)), arg);
      else
        return convert (TREE_TYPE (arg), integer_zero_node);


So there is no check for TREE_SIDE_EFFECTS.  Maybe it should use
omit_one_operand or build a COMPOUND_EXPR.  Either one will fix the
bug.

-- Pinski


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33192

[Bug c/33192] __imag operator drops side effects in subexpr

[rguenth at gcc dot gnu dot org]

------- Comment #2 from rguenth at gcc dot gnu dot org  2007-08-26 14:56 -------
Confirmed.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rguenth at gcc dot gnu dot
                   |                            |org
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
           Keywords|                            |wrong-code
   Last reconfirmed|0000-00-00 00:00:00         |2007-08-26 14:56:26
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33192

[Bug c/33192] __imag operator drops side effects in subexpr

[jsm28 at gcc dot gnu dot org]

------- Comment #3 from jsm28 at gcc dot gnu dot org  2008-10-16 17:07 -------
Subject: Bug 33192

Author: jsm28
Date: Thu Oct 16 17:05:57 2008
New Revision: 141176

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=141176
Log:
        PR c/33192
        * c-typeck.c (build_unary_op): Use omit_one_operand for
        IMAGPART_EXPR of real argument.

testsuite:
        * gcc.dg/imag-1.c: New test.

Added:
    trunk/gcc/testsuite/gcc.dg/imag-1.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/c-typeck.c
    trunk/gcc/testsuite/ChangeLog


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33192

[Bug c/33192] __imag operator drops side effects in subexpr

[jsm28 at gcc dot gnu dot org]

------- Comment #4 from jsm28 at gcc dot gnu dot org  2008-10-16 17:12 -------
Fixed for 4.4.


-- 

jsm28 at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.4.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33192