[Bug c++/41840] New: g++ compiler giving error for array of pointers of abstract base class

[ganesh dot borse at credit-suisse dot com]

Following code is not compiling with g++ 4.2.3, but compiles fine with g++
3.3.3:
==========================
#include<iostream>
class mybase {
   public:
     virtual int afunc()=0;
};
main()
{
  mybase (*ptrs)[10];
}
==========================
Error given by g++4.2.3 is as below for the above code. I am using following
simple command to compile the command, without any options, flags
# g++ testpure.cpp
testpure.cpp: In function âint main()â:
testpure.cpp:10: error: invalid abstract type âmybaseâ for âptrsâ
testpure.cpp:3: note:   because the following virtual functions are pure within
âmybaseâ:
testpure.cpp:5: note:   virtual int mybase::afunc()
==========================
Information about compiler, OS, Kernel on which I am seeing this issue is as
below:
(1) Compiler information:
g++ -v
Using built-in specs.
Target: x86_64-unknown-linux-gnu
Configured with: ./configure --prefix=/app/devtools/gcc-4.2.3
--exec-prefix=/app/devtools/gcc-4.2.3 --with-mpfr=/app/devtools/mpfr-2.2.1
--with-mpfr-include=/app/devtools/mpfr-2.2.1
--with-mpfr-lib=/app/devtools/mpfr-2.2.1/.libs
--with-gmp=/app/devtools/gmp-4.2.2 --with-gmp-include=/app/devtools/gmp-4.2.2
--with-gmp-lib=/app/devtools/gmp-4.2.2/.libs --enable-languages=c,c++,fortran
Thread model: posix
gcc version 4.2.3

(2) OS Information:
cat /etc/SuSE-release
SUSE Linux Enterprise Server 10 (x86_64)
VERSION = 10
PATCHLEVEL = 1
-------------
uname -a
Linux vsgl36a-1031 2.6.16.46-0.12-smp #1 SMP Thu May 17 14:00:09 UTC 2007
x86_64 x86_64 x86_64 GNU/Linux
==========================

Can I please know why g++4.2.3 is behaving differently that g++ 3.3.3?

According to C++, we can declare the pointer(s) of abstract base class. But why
is g++ 4.2.3 compiler not allowing to even declare these pointers?

Is this a bug in g++4.2.3?
In which release of g++, this bug is fixed?

There are many other such deviations we noticed in this compiler from the
normal C++ principles.

Should we not use g++ 4.2.3? Which is the most stable version in g++ 4.x.x
series?

Please help.

------------------------------------------
Output of :g++ -v -save-temps testpure.cpp
Using built-in specs.
Target: x86_64-unknown-linux-gnu
Configured with: ./configure --prefix=/app/devtools/gcc-4.2.3
--exec-prefix=/app/devtools/gcc-4.2.3 --with-mpfr=/app/devtools/mpfr-2.2.1
--with-mpfr-include=/app/devtools/mpfr-2.2.1
--with-mpfr-lib=/app/devtools/mpfr-2.2.1/.libs
--with-gmp=/app/devtools/gmp-4.2.2 --with-gmp-include=/app/devtools/gmp-4.2.2
--with-gmp-lib=/app/devtools/gmp-4.2.2/.libs --enable-languages=c,c++,fortran
Thread model: posix
gcc version 4.2.3
 /app/devtools/gcc-4.2.3/libexec/gcc/x86_64-unknown-linux-gnu/4.2.3/cc1plus -E
-quiet -v -D_GNU_SOURCE testpure.cpp -mtune=generic -fpch-preprocess -o
testpure.ii
ignoring nonexistent directory
"/app/devtools/gcc-4.2.3/lib/gcc/x86_64-unknown-linux-gnu/4.2.3/../../../../x86_64-unknown-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:

/app/devtools/gcc-4.2.3/lib/gcc/x86_64-unknown-linux-gnu/4.2.3/../../../../include/c++/4.2.3

/app/devtools/gcc-4.2.3/lib/gcc/x86_64-unknown-linux-gnu/4.2.3/../../../../include/c++/4.2.3/x86_64-unknown-linux-gnu

/app/devtools/gcc-4.2.3/lib/gcc/x86_64-unknown-linux-gnu/4.2.3/../../../../include/c++/4.2.3/backward
 /usr/local/include
 /app/devtools/gcc-4.2.3/include
 /app/devtools/gcc-4.2.3/lib/gcc/x86_64-unknown-linux-gnu/4.2.3/include
 /usr/include
End of search list.
 /app/devtools/gcc-4.2.3/libexec/gcc/x86_64-unknown-linux-gnu/4.2.3/cc1plus
-fpreprocessed testpure.ii -quiet -dumpbase testpure.cpp -mtune=generic
-auxbase testpure -version -o testpure.s
GNU C++ version 4.2.3 (x86_64-unknown-linux-gnu)
        compiled by GNU C version 4.2.3.
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: 4f1a9dd65e939519bf89a9e8788cb5ba
testpure.cpp: In function âint main()â:
testpure.cpp:10: error: invalid abstract type âmybaseâ for âptrsâ
testpure.cpp:3: note:   because the following virtual functions are pure within
âmybaseâ:
testpure.cpp:5: note:   virtual int mybase::afunc()
======================================================
cat testpure.s
        .file   "testpure.cpp"
        .section        .ctors,"aw",@progbits
        .align 8
        .quad   _GLOBAL__I_main


-- 
           Summary: g++ compiler giving error for array of pointers of
                    abstract base class
           Product: gcc
           Version: 4.2.3
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: ganesh dot borse at credit-suisse dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41840