[Bug c++/38613] New: extern template suppresses VFT but should not

hstong at ca dot ibm dot com gcc-bugzilla@gcc.gnu.org
Tue Dec 23 21:31:00 GMT 2008 

Rejects valid.  The following test case fails to link because VFTs are missing.
Based on the C++0x draft (N2800), this program should compile, link and run
successfully.

This appears to be a problem with the GCC implementation of explicit
instantiation
declarations, i.e. extern template.

The source consists of one file with no #include.

> cat a.cpp
template <class T>
struct A {
   A();
   A(A const &);
   A &operator =(A const &);
   ~A();
   virtual int foo();
};

template <class T>
A<T>::A() { }

template <class T>
A<T>::A(A const &) { }

template <class T>
A<T> &A<T>::operator =(A const &) { return *this; }

template <class T>
A<T>::~A() { }

template <class T>
int A<T>::foo(void) {
   return 42;
}

// explicit instantiation declaration of a class does not affect the class
itself
// but is an explicit instantiation declaration of each of its members
extern template struct A<int>;

// we provide explicit instantiation definitions of all the members of struct
A<int> here
template A<int>::A();
template A<int>::A(A const &);
template A<int> &A<int>::operator =(A const &);
template A<int>::~A();
template int A<int>::foo();

int main(void) {
   A<int> a;  // constructor needs to set VFT for `a'
   return 0;
}

> /compilers/g++-4.3.2 -std=c++0x -v -c a.cpp -o a.o
Using built-in specs.
Target: powerpc64-unknown-linux-gnu
Configured with: /data/gcc/src/gcc-4.3.2/configure --prefix=/data/gcc
--program-suffix=-4.3.2 --disable-libssp --disable-libgcj
--enable-version-specific-runtime-libs --with-cpu=default32 --enable-secureplt
--with-long-double-128 --enable-shared --enable-__cxa_atexit
--enable-threads=posix --enable-languages=c,c++
Thread model: posix
gcc version 4.3.2 (GCC)
COLLECT_GCC_OPTIONS='-std=c++0x' '-v' '-c' '-o' 'a.o' '-shared-libgcc'
 /data/gcc/libexec/gcc/powerpc64-unknown-linux-gnu/4.3.2/cc1plus -quiet -v
-D_GNU_SOURCE -D__unix__ -D__gnu_linux__ -D__linux__ -Asystem=linux
-Asystem=unix -Asystem=posix a.cpp -msecure-plt -quiet -dumpbase a.cpp
-auxbase-strip a.o -std=c++0x -version -o
data/gcc/lib/gcc/powerpc64-unknown-linux-gnu/4.3.2/../../../../powerpc64-unknown-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
 /data/gcc/lib/gcc/powerpc64-unknown-linux-gnu/4.3.2/include/c++

/data/gcc/lib/gcc/powerpc64-unknown-linux-gnu/4.3.2/include/c++/powerpc64-unknown-linux-gnu
 /data/gcc/lib/gcc/powerpc64-unknown-linux-gnu/4.3.2/include/c++/backward
 /usr/local/include
 /data/gcc/include
 /data/gcc/lib/gcc/powerpc64-unknown-linux-gnu/4.3.2/include
 /data/gcc/lib/gcc/powerpc64-unknown-linux-gnu/4.3.2/include-fixed
 /usr/include
End of search list.
GNU C++ (GCC) version 4.3.2 (powerpc64-unknown-linux-gnu)
        compiled by GNU C version 4.3.2, GMP version 4.1.4, MPFR version 2.2.1.
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: d61d206a8be21ae59ecbfeb94562168a
COLLECT_GCC_OPTIONS='-std=c++0x' '-v' '-c' '-o' 'a.o' '-shared-libgcc'
 as -a32 -mppc -many -V -Qy -o a.o
data/gcc/libexec/gcc/powerpc64-unknown-linux-gnu/4.3.2/:/data/gcc/libexec/gcc/powerpc64-unknown-linux-gnu/4.3.2/:/data/gcc/libexec/gcc/powerpc64-unknown-linux-gnu/:/data/gcc/lib/gcc/powerpc64-unknown-linux-gnu/4.3.2/:/data/gcc/lib/gcc/powerpc64-unknown-linux-gnu/
LIBRARY_PATH=/data/gcc/lib/gcc/powerpc64-unknown-linux-gnu/4.3.2/:/data/gcc/lib/gcc/powerpc64-unknown-linux-gnu/4.3.2/../../../../lib/:/lib/../lib/:/usr/lib/../lib/:/data/gcc/lib/gcc/powerpc64-unknown-linux-gnu/4.3.2/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-std=c++0x' '-v' '-c' '-o' 'a.o' '-shared-libgcc'

> /compilers/g++-4.3.2 -std=c++0x -v a.o -o a.out
Using built-in specs.
Target: powerpc64-unknown-linux-gnu
Configured with: /data/gcc/src/gcc-4.3.2/configure --prefix=/data/gcc
--program-suffix=-4.3.2 --disable-libssp --disable-libgcj
--enable-version-specific-runtime-libs --with-cpu=default32 --enable-secureplt
--with-long-double-128 --enable-shared --enable-__cxa_atexit
--enable-threads=posix --enable-languages=c,c++
Thread model: posix
gcc version 4.3.2 (GCC)
COMPILER_PATH=/data/gcc/libexec/gcc/powerpc64-unknown-linux-gnu/4.3.2/:/data/gcc/libexec/gcc/powerpc64-unknown-linux-gnu/4.3.2/:/data/gcc/libexec/gcc/powerpc64-unknown-linux-gnu/:/data/gcc/lib/gcc/powerpc64-unknown-linux-gnu/4.3.2/:/data/gcc/lib/gcc/powerpc64-unknown-linux-gnu/
LIBRARY_PATH=/data/gcc/lib/gcc/powerpc64-unknown-linux-gnu/4.3.2/:/data/gcc/lib/gcc/powerpc64-unknown-linux-gnu/4.3.2/../../../../lib/:/lib/../lib/:/usr/lib/../lib/:/data/gcc/lib/gcc/powerpc64-unknown-linux-gnu/4.3.2/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-std=c++0x' '-v' '-o' 'a.out' '-shared-libgcc'
 /data/gcc/libexec/gcc/powerpc64-unknown-linux-gnu/4.3.2/collect2
--eh-frame-hdr -V -Qy -m elf32ppclinux -dynamic-linker /lib/ld.so.1 -o a.out
/usr/lib/../lib/crt1.o /usr/lib/../lib/crti.o
/data/gcc/lib/gcc/powerpc64-unknown-linux-gnu/4.3.2/crtbegin.o
-L/data/gcc/lib/gcc/powerpc64-unknown-linux-gnu/4.3.2
-L/data/gcc/lib/gcc/powerpc64-unknown-linux-gnu/4.3.2/../../../../lib
-L/lib/../lib -L/usr/lib/../lib
-L/data/gcc/lib/gcc/powerpc64-unknown-linux-gnu/4.3.2/../../.. a.o -lstdc++ -lm
-lgcc_s -lgcc -lc -lgcc_s -lgcc
/data/gcc/lib/gcc/powerpc64-unknown-linux-gnu/4.3.2/crtsavres.o
/data/gcc/lib/gcc/powerpc64-unknown-linux-gnu/4.3.2/crtend.o
/usr/lib/../lib/crtn.o
GNU ld version 2.16.91.0.5 20051219 (SUSE Linux)
  Supported emulations:
   elf32ppclinux
   elf32ppc
   elf32ppcsim
   elf64alpha
   alpha
   armelf_linux
   armelf
   hppalinux
   elf_i386
   i386linux
   elf64_ia64
   m68kelf
   m68klinux
   elf64ppc
   elf_s390
   elf64_s390
   elf32_sparc
   sparclinux
   elf64_sparc
   sun4
   elf_x86_64
   ppcmacosa.o: In function `A<int>::A()':
a.cpp:(.text._ZN1AIiEC2Ev[A<int>::A()]+0x16): undefined reference to `vtable
for A<int>'
a.cpp:(.text._ZN1AIiEC2Ev[A<int>::A()]+0x1a): undefined reference to `vtable
for A<int>'
a.o: In function `A<int>::A()':
a.cpp:(.text._ZN1AIiEC1Ev[A<int>::A()]+0x16): undefined reference to `vtable
for A<int>'
a.cpp:(.text._ZN1AIiEC1Ev[A<int>::A()]+0x1a): undefined reference to `vtable
for A<int>'
a.o: In function `A<int>::A(A<int> const&)':
a.cpp:(.text._ZN1AIiEC2ERKS0_[A<int>::A(A<int> const&)]+0x1a): undefined
reference to `vtable for A<int>'
a.o:a.cpp:(.text._ZN1AIiEC2ERKS0_[A<int>::A(A<int> const&)]+0x1e): more
undefined references to `vtable for A<int>' follow
collect2: ld returned 1 exit status


-- 
           Summary: extern template suppresses VFT but should not
           Product: gcc
           Version: 4.3.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: hstong at ca dot ibm dot com
 GCC build triplet: powerpc64-suse-linux
  GCC host triplet: powerpc64-unknown-linux-gnu
GCC target triplet: powerpc64-unknown-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38613

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