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From "Martin Sebor (JIRA)" <j...@apache.org>
Subject [jira] Commented: (STDCXX-262) [gcc 4.0.1/Mac OS X 10.4.6 Tiger] multiple vtable definitions for bad_exception and bad_alloc
Date Thu, 27 Sep 2007 00:32:50 GMT

    [ https://issues.apache.org/jira/browse/STDCXX-262?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12530605
] 

Martin Sebor commented on STDCXX-262:
-------------------------------------

Here's an analysis of what's going on in stdcxx:

1, On Mac OS X, gcc 4.0.1 doesn't generate a vtable for class E in the test case below (which
is as expected given that the class dtor isn't defined) but it does so for class D (which
is not expected because this dtor also isn't defined), even though there is no "real" difference
between the two classes other than the order in which the members are declared.

2. We declare members of std::exception, std::bad_exception, and std::bad_alloc in the same
order as those in class D below, i.e., the dtor comes before the other virtual member function.
Since we also define some virtual members of these classes (based on the results of config
tests which determine that some members are not defined in libsupc++), the vtable for each
is generated in the object file where the other members are defined. Since the vtable for
all these classes also exists in libsupc++ (that's where the virtual dtor and what() are defined),
we end up with two vtables for each class.

3. Given the above, we should be able to work around the problem by reversing the declaration
order of the virtual dtor and the other virtual member (what()) so as to trick the compiler
into not generating the vtable in our objects.

$ cat t.cpp && uname -srp && gcc -dumpversion && gcc -c t.cpp &&
nm t.o | c++filt | grep "S vtable"
struct B {
    virtual ~B ();
    virtual void foo ();
};

struct D: B {
    virtual void foo ();
    virtual ~D ();
};

struct E: B {
    virtual ~E ();
    virtual void foo ();
};

void D::foo () { }
void E::foo () { }

Darwin 8.7.1 i386
4.0.1
00000020 S vtable for D

> [gcc 4.0.1/Mac OS X 10.4.6 Tiger] multiple vtable definitions for bad_exception and bad_alloc
> ---------------------------------------------------------------------------------------------
>
>                 Key: STDCXX-262
>                 URL: https://issues.apache.org/jira/browse/STDCXX-262
>             Project: C++ Standard Library
>          Issue Type: Bug
>          Components: Build
>    Affects Versions: 4.1.3
>         Environment: Darwin machine.local 8.7.1 Darwin Kernel Version 8.7.1: Wed Jun
 7 16:19:56 PDT 2006; root:xnu-792.9.72.obj~2/RELEASE_I386 i386 i386
>            Reporter: Eric Lemings
>            Assignee: Martin Sebor
>            Priority: Critical
>             Fix For: 4.2
>
>
> machine:~/Work user$ svn co http://svn.apache.org/repos/asf/incubator/stdcxx/trunk stdcxx
> A    stdcxx/generate.bat
> A    stdcxx/LICENSE.txt
> A    stdcxx/tests
> A    stdcxx/tests/tr1.util
> ...
> A    stdcxx/examples/manual/time_put.cpp
> A    stdcxx/examples/manual/moneyget.cpp
> A    stdcxx/examples/manual/except.cpp
> A    stdcxx/examples/manual/memfunc.cpp
> Checked out revision 423638.
> machine:~/Work user$ cd stdcxx
> machine:~/Work/stdcxx user$ make BUILDDIR="~/Build" BUILDMODE="debug,shared,pthreads"
> creating BUILDDIR=/Users/user/Build/stdcxx
> generating /Users/user/Build/stdcxx/makefile.in from /Users/user/Work/stdcxx/etc/config/gcc.config
> make config
> configuring for gcc-4.0.1 on darwin-8.7.1-i386
> checking if the compiler is sane                   ok (invoked with gcc)
> checking if the linker is sane                     ok (invoked with gcc)
> checking system architecture                       ILP32 little endian
> ...
> gcc -c -I/Users/user/Work/stdcxx/include/ansi -D_RWSTDDEBUG    -D_RWSTD_USE_CONFIG -I/Users/user/Work/stdcxx/include
-I/Users/user/Build/stdcxx/include  -pedantic -nostdinc++ -g  -W -Wall -Wcast-qual -Winline
-Wshadow -Wwrite-strings -Wno-long-long -Wcast-align  -fPIC /Users/user/Work/stdcxx/src/wctype.cpp
> gcc      assert.o atomic-cxx.o bitset.o catalog.o codecvt.o collate.o ctype.o ctype_bits.o
exception.o export.o facet.o file.o instance.o ios.o ios_bits.o iostore.o iostream.o iso2022.o
limits.o limits_bits.o locale_bits.o locale_body.o locale_classic.o locale_combine.o locale_core.o
locale_eq.o locale_global.o locale_name.o memattr.o memory.o messages.o num_get.o num_put.o
punct.o random.o setlocale.o string.o strstream.o strtol.o ti_collate.o ti_filebuf.o ti_insert_dbl.o
ti_insert_int.o ti_insert_ptr.o ti_ios.o ti_istream.o ti_messages.o ti_money_get.o ti_money_put.o
ti_moneypunct.o ti_num_get.o ti_num_put.o ti_numpunct.o ti_ostream.o ti_streambuf.o ti_string.o
ti_stringbuf.o ti_time_get.o ti_time_put.o ti_wcollate.o ti_wfilebuf.o ti_winsert_dbl.o ti_winsert_int.o
ti_winsert_ptr.o ti_wios.o ti_wistream.o ti_wmessages.o ti_wmoney_get.o ti_wmoney_put.o ti_wmoneypunct.o
ti_wnum_get.o ti_wnum_put.o ti_wnumpunct.o ti_wostream.o ti_wstreambuf.o ti_wstring.o ti_wstringbuf.o
ti_wtime_get.o ti_wtime_put.o time_get.o time_put.o tmpbuf.o typeinfo.o valarray.o vecbool.o
version.o wcodecvt.o wctype.o -lsupc++ -lgcc_eh -o /Users/user/Build/stdcxx/lib/libstd.dylib.4.2.0

> /usr/bin/ld: multiple definitions of symbol vtable for std::bad_exception
> exception.o definition of vtable for std::bad_exceptionin section (__DATA,__const)
> /usr/lib/gcc/i686-apple-darwin8/4.0.1/../../../libsupc++.a(eh_exception.o) private external
definition of vtable for std::bad_exceptionin section (__DATA,__const)
> /usr/bin/ld: multiple definitions of symbol vtable for std::bad_alloc
> memory.o definition of vtable for std::bad_allocin section (__DATA,__const)
> /usr/lib/gcc/i686-apple-darwin8/4.0.1/../../../libsupc++.a(new_handler.o) private external
definition of vtable for std::bad_allocin section (__DATA,__const)
> collect2: ld returned 1 exit status
> make[2]: *** [/Users/user/Build/stdcxx/lib/libstd.dylib] Error 1
> make[1]: *** [lib] Error 2
> make: *** [libstd] Error 2

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