[Bug c/14661] New: ?: operator result structure's member array can't be assigned to pointer

[Bug c/14661] New: ?: operator result structure's member array can't be assigned to pointer

[dmj36 at email dot byu dot edu]

Reading specs from /usr/lib/gcc-lib/i686-pc-cygwin/3.3.1/specs
Configured with: /netrel/src/gcc-3.3.1-2/configure --enable-
languages=c,c++,f77,java --enable-libgcj --enable-threads=posix --with-system-
zlib --enable-nls --without-included-gettext --enable-interpreter --enable-sjlj-
exceptions --disable-version-specific-runtime-libs --enable-shared --build=i686-
pc-linux --host=i686-pc-cygwin --target=i686-pc-cygwin --prefix=/usr --exec-
prefix=/usr --sysconfdir=/etc --libdir=/usr/lib --
includedir=/nonexistent/include --libexecdir=/usr/sbin
Thread model: posix
gcc version 3.3.1 (cygming special)
 /usr/lib/gcc-lib/i686-pc-cygwin/3.3.1/cc1.exe -E -quiet -v -D__GNUC__=3 -
D__GNUC_MINOR__=3 -D__GNUC_PATCHLEVEL__=1 -D__CYGWIN32__ -D__CYGWIN__ -Dunix -
D__unix__ -D__unix -idirafter /usr/lib/gcc-lib/i686-pc-
cygwin/3.3.1/../../../../include/w32api -idirafter /usr/lib/gcc-lib/i686-pc-
cygwin/3.3.1/../../../../i686-pc-cygwin/lib/../../include/w32api breaks-gcc.c 
breaks-gcc.i
ignoring nonexistent directory "/usr/local/include"
ignoring nonexistent directory "/usr/i686-pc-cygwin/include"
ignoring duplicate directory "/usr/i686-pc-cygwin/lib/../../include/w32api"
#include "..." search starts here:
#include <...> search starts here:
 /usr/lib/gcc-lib/i686-pc-cygwin/3.3.1/include
 /usr/include
 /usr/include/w32api
End of search list.
 /usr/lib/gcc-lib/i686-pc-cygwin/3.3.1/cc1.exe -fpreprocessed breaks-gcc.i -
quiet -dumpbase breaks-gcc.c -auxbase breaks-gcc -version -o breaks-gcc.s
GNU C version 3.3.1 (cygming special) (i686-pc-cygwin)
	compiled by GNU C version 3.3.1 (cygming special).
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
breaks-gcc.c: In function `main':
breaks-gcc.c:23: internal compiler error: in emit_move_insn, at expr.c:3156
Please submit a full bug report,
with preprocessed source if appropriate.
See <URL:http://gcc.gnu.org/bugs.html> for instructions.


Source file (breaks-gcc.i):

# 1 "breaks-gcc.c"
# 1 "<built-in>"
# 1 "<command line>"
# 1 "breaks-gcc.c"
typedef unsigned short Uint16;

typedef struct Data_Struct {
    Uint16 lever_arm[3];
} Data_Struct;

typedef enum Local_Foreign_Type {
    LOCAL = 1,
    FOREIGN = 2
} Local_Foreign_Type;

Data_Struct Local_Data = { { LOCAL, LOCAL, LOCAL } };
Data_Struct Foreign_Data = { { FOREIGN, FOREIGN, FOREIGN } };

int main(int argc, char *argv[]) {
    Local_Foreign_Type source = LOCAL;

    Uint16 *foo = (((((source) == FOREIGN) ? Foreign_Data : 
Local_Data)).lever_arm);
# 43 "breaks-gcc.c"
    return 0;
}

-- 
           Summary: ?: operator result structure's member array can't be
                    assigned to pointer
           Product: gcc
           Version: 3.3.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: dmj36 at email dot byu dot edu
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14661

[Bug c/14661] [3.3? Regression] ?: operator result structure's member array can't be assigned to pointer

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-03-20 01:31 -------
I did not confirm this because I do not have a newer 3.3 gcc.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |ice-on-invalid-code
      Known to fail|                            |3.3.1
      Known to work|                            |3.4.0 3.5.0 3.0.4 3.2.3
            Summary|?: operator result          |[3.3? Regression] ?:
                   |structure's member array    |operator result structure's
                   |can't be assigned to pointer|member array can't be
                   |                            |assigned to pointer
   Target Milestone|---                         |3.3.4


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14661

[Bug c/14661] [3.3? Regression] ?: operator result structure's member array can't be assigned to pointer

[reichelt at gcc dot gnu dot org]

------- Additional Comments From reichelt at gcc dot gnu dot org  2004-03-20 02:54 -------
The code used to compile with gcc 2.95.x - 3.0.x, but ICEd with 3.1 - 3.3.1.
Since gcc 3.3.2 the ICE is gone - the code is rejected.

But is the code really invalid?
The code does compile as C++ source or with the option "-std=c99".
It also compiles, if I replace the condition (source == FOREIGN)
with a constant.

Here's a shorter example that demonstrates the problem:

======================================
struct A
{
    char str[1];
};

struct A a = { "" };
struct A b = { "" };

void foo (int i)
{
    char *p = ( i ? a : b ).str;
}
======================================


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |reichelt at gcc dot gnu dot
                   |                            |org
      Known to fail|3.3.1                       |3.1 3.1.1 3.1.2 3.2 3.2.1
                   |                            |3.2.2 3.2.3 3.3 3.3.1
      Known to work|3.4.0 3.5.0 3.0.4 3.2.3     |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14661

[Bug c/14661] [3.3? Regression] ?: operator result structure's member array can't be assigned to pointer

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2004-03-22 02:20 -------
In C, the result of the ?: operator is an rvalue, i.e. 
  ( i ? a : b ) 
is a temporary of type A, and taking the address of its member 
is assigning the address of a temporary to the result variable. 
That should be legal, but should also yield undefined behavior. 
 
W. 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14661

[Bug c/14661] [3.3?/3.4/3.5 Regression] ?: operator result structure's member array can't be assigned to pointer

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |rejects-valid
            Summary|[3.3? Regression] ?:        |[3.3?/3.4/3.5 Regression] ?:
                   |operator result structure's |operator result structure's
                   |member array can't be       |member array can't be
                   |assigned to pointer         |assigned to pointer


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14661

[Bug c/14661] [3.3?/3.4/3.5 Regression] ?: operator result structure's member array can't be assigned to pointer

[jsm at polyomino dot org dot uk]

------- Additional Comments From jsm at polyomino dot org dot uk  2004-03-22 09:52 -------
Subject: Re:  [3.3? Regression] ?: operator result structure's
 member array can't be assigned to pointer

On Mon, 22 Mar 2004, bangerth at dealii dot org wrote:

> In C, the result of the ?: operator is an rvalue, i.e. 
>   ( i ? a : b ) 
> is a temporary of type A, and taking the address of its member 
> is assigning the address of a temporary to the result variable. 
> That should be legal, but should also yield undefined behavior. 

But only C99 allows the non-lvalue array to convert to a pointer like
that.



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14661

[Bug c/14661] [3.3? Regression] ?: operator result structure's member array can't be assigned to pointer

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|rejects-valid               |
            Summary|[3.3?/3.4/3.5 Regression] ?:|[3.3? Regression] ?:
                   |operator result structure's |operator result structure's
                   |member array can't be       |member array can't be
                   |assigned to pointer         |assigned to pointer


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14661

[Bug c/14661] [3.3? Regression] ?: operator result structure's member array can't be assigned to pointer

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2004-04-06 13:33 -------
Given my and Joseph's comments, I understand that gcc's behavior is to 
be expected.  
 
W. 

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
      Known to work|                            |3.3.2
         Resolution|                            |INVALID
   Target Milestone|3.3.4                       |3.3.2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14661