[Bug c/51741] New: complicatet brakets wont compile

[Bug c/51741] New: complicatet brakets wont compile

[digsag at web dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51741

             Bug #: 51741
           Summary: complicatet brakets wont compile
    Classification: Unclassified
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: minor
          Priority: P3
         Component: c
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: digsag@web.de


flowing structure:
typedef struct{//branch
 char what;
 void *where;      //cast to knot *
}branch;
typedef struct{//knot
 void *father;     //cast to knot *
 branch *branches;
}knot;

adressing a knot** to hand it to a subfun wont compile:


            // (*pos)
            // (      .branches)
           // (                 [i])
          // (                      .where)
  // ((knot*)                              )
// (&                                       )
   (&((knot*)((((*pos).branches)[i]).where)))

(compiler sas lvaluve needed for unary & operator)

but 

               // (*pos)
              // (      .branches)
             // (                 [i])
            // (                      .where)
          // (&                              )
 // ((knot**)                                 )
    ((knot**)(&((((*pos).branches)[i]).where)))
    ((knot**)(&((((*pos).branches)[i]).where)))
will.
both seem like legal C to me.

another one:


            // (*pos)
           // (      .branches)
          // (                 [0])
         // (                      .where)
 // ((knot*)                              )
// (                                       .father)
   (((knot*)((((*pos).branches)[0]).where)).father)=pos;

won't compile .
compiler thinks I try to adress .father for something thats not a structure or
a union. even though I castet it to a knot* before trying to adress .father.


yours
stfu&thnk

[Bug c/51741] complicatet brakets wont compile

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51741

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID

--- Comment #1 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-01-03 15:18:34 UTC ---
as soon as you cast the .where pointer to some other type it converts to
an rvalue.  Use (knot*)&(....where) instead of &(knot *)(...where).

[Bug c/51741] complicatet brakets wont compile

[digsag at web dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51741

--- Comment #2 from stfu&thnk <digsag at web dot de> 2012-01-03 15:21:26 UTC ---
I fail &secon one. forgot a * -.-

[Bug c/51741] complicatet brakets wont compile

[digsag at web dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51741

--- Comment #3 from stfu&thnk <digsag at web dot de> 2012-01-03 15:23:12 UTC ---
(In reply to comment #1)
> as soon as you cast the .where pointer to some other type it converts to
> an rvalue.  Use (knot*)&(....where) instead of &(knot *)(...where).

I don't know how the first one is non-valid C. seems valid in my eyes...

[Bug c/51741] complicatet brakets wont compile

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51741

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-01-03 15:25:32 UTC ---
The bug reporting guidelines at http://gcc.gnu.org/bugs/ ask for the following
which you have not provided:

* the exact version of gcc
* the exact command line
* the complete preprocessed source, not some code snippets (what is pos?)


(In reply to comment #0)
>    (&((knot*)((((*pos).branches)[i]).where)))
> 
> (compiler sas lvaluve needed for unary & operator)

The compiler is correct.  The cast to (knot*) creates an rvalue, so you cannot
take its address.

>     ((knot**)(&((((*pos).branches)[i]).where)))

Here you take the address of an lvalue, then cast it to (knot**), that's legal.

> will.
> both seem like legal C to me.

No, the first one is not. The bug is in your code, not GCC.


>    (((knot*)((((*pos).branches)[0]).where)).father)=pos;
> 
> won't compile .
> compiler thinks I try to adress .father for something thats not a structure or
> a union. even though I castet it to a knot* before trying to adress .father.

Maybe you mean ->father not .father.

Just because your code doesn't compile, that doesn't mean it's a GCC bug.

[Bug c/51741] complicatet brakets wont compile

[digsag at web dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51741

--- Comment #5 from stfu&thnk <digsag at web dot de> 2012-01-03 15:47:08 UTC ---
yeah i just realised how the second one was a fail of my side.

but I didn't realze the rvalue lvalue stuff.


thanx for the help, and please don't go all pissed off I didn't want to insult
you...

but well if you feel like an adult flaming at noobs, please go on :-P

[Bug c/51741] complicatet brakets wont compile

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51741

--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-01-03 15:53:13 UTC ---
noone's insulted and noone's flaming, but in future please follow the bug
reporting guidelines (and maybe check with someone who knows C well before
assuming the compiler is wrong, e.g. ask on a newsgroup or on IRC channel for
the C language)