[Bug c++/29909] New: g++ does not enforce the same regparm(X) on overridden virtual methods

[Bug c++/29909] New: g++ does not enforce the same regparm(X) on overridden virtual methods

[massimiliano dot ghilardi at gmail dot com]

This is the first of 3 related g++ bugs concerning regparm(3) on ix86.

Problem: g++ 3.4.6, 4.0.4, 4.1.2 (and possibly others) do not check or enforce
the same __attribute((regparm(X))) on overridden virtual methods.

It is possible for example for a method tagged __attribute((regparm(0)))
to override a method tagged __attribute((regparm(3))).

The problem is particularly severe when a Base class declares an
__attribute((regparm(X))) virtual destructor (with X>0),
and a Derived class does NOT declare an explicit destructor:
the compiler-generated virtual destructor of the Derived class will be
__attribute((regparm(0))), and the compiled program will SEGFAULT.


Test case:

--------------------------------------------------
// compile on ix86 with: g++ -Wall -O

class Base {
public:
    virtual __attribute((regparm(3))) ~Base() { }
};

class Derived : public Base {
public:
    virtual ~Derived() { }
};

int main() {
    Base * s = new Derived();
    delete s;

    return 0;
}
--------------------------------------------------


gcc versions tested: 3.4.6, 4.0.4, 4.1.2

>>>>> g++-3.4.6 -v <<<<<
Reading specs from /usr/lib/gcc/i486-linux-gnu/3.4.6/specs 
Configured with: ../src/configure -v --enable-languages=c,c++,f77,pascal
--prefix=/usr --libexecdir=/usr/lib --with-gxx-include-dir=/usr/include/c++/3.4
--enable-shared --with-system-zlib --enable-nls --without-included-gettext
--program-suffix=-3.4 --enable-__cxa_atexit --enable-clocale=gnu
--enable-libstdcxx-debug --with-tune=i686 i486-linux-gnu
Thread model: posix                                                            
                                                              gcc version 3.4.6
(Debian 3.4.6-4)

>>>>> g++-4.0.4 -v <<<<<
Using built-in specs.
Target: i486-linux-gnu
Configured with: ../src/configure -v --enable-languages=c,c++,java
--prefix=/usr --enable-shared --with-system-zlib --libexecdir=/usr/lib
--without-included-gettext --enable-threads=posix --enable-nls
--program-suffix=-4.0 --enable-__cxa_atexit --enable-clocale=gnu
--enable-libstdcxx-debug --enable-java-awt=gtk-default --enable-gtk-cairo
--with-java-home=/usr/lib/jvm/java-1.4.2-gcj-4.0-1.4.2.0/jre --with-tune=i686
--enable-checking=release i486-linux-gnu
Thread model: posix
gcc version 4.0.4 20060904 (prerelease) (Debian 4.0.3-7)

>>>>> g++-4.1.2 -v <<<<<
Using built-in specs.
Target: i486-linux-gnu
Configured with: ../src/configure -v
--enable-languages=c,c++,fortran,objc,obj-c++,treelang --prefix=/usr
--enable-shared --with-system-zlib --libexecdir=/usr/lib
--without-included-gettext --enable-threads=posix --enable-nls
--program-suffix=-4.1 --enable-__cxa_atexit --enable-clocale=gnu
--enable-libstdcxx-debug --enable-mpfr --with-tune=i686
--enable-checking=release i486-linux-gnu
Thread model: posix
gcc version 4.1.2 20061115 (prerelease) (Debian 4.1.1-20)


-- 
           Summary: g++ does not enforce the same regparm(X) on overridden
                    virtual methods
           Product: gcc
           Version: 4.1.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: massimiliano dot ghilardi at gmail dot com
 GCC build triplet: i486-linux-gnu
  GCC host triplet: i486-linux-gnu
GCC target triplet: i486-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29909

[Bug c++/29909] g++ does not enforce the same regparm(X) on overridden virtual methods

[massimiliano dot ghilardi at gmail dot com]

------- Comment #1 from massimiliano dot ghilardi at gmail dot com  2006-11-20 12:21 -------


*** This bug has been marked as a duplicate of 14688 ***


-- 

massimiliano dot ghilardi at gmail dot com changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29909