pragma in 3.2.x

Scott A. Smith
Tue Oct 22 05:33:00 GMT 2002


I get lots of "undefined reference" errors when linking to my static
libraries under GCC-3.2. I think I have isolated the problem, it stems from
#pragma interface in my headers. Here is a simple example:


#include "PSet.h"
int PSet::Psize() { return size(); }

======= PSet.h

#include <list>

//#ifdef __GNUG__
//#pragma interface

class PSet : public std::list<double> {
  int PSet::Psize();


#include <iostream>
#include "PSet.h"                               // Include our derived list

int main()
  std::cout << std::endl << std::endl;
  std::cout << "\n\tHello World";
  PSet ps;
  std::cout << "\n\tSize is " << ps.Psize();
  std::cout << std::endl << std::endl;


If I build a static library containing class PSet with the following:

g++ -c -I.
ar r libpset.a PSet.o
ranlib libpset.a

and then compile/link/run the "" program with this

g++ -I. -L. -lpset

Everything works fine, BUT if I uncomment the three lines in PSet.h that
use "pragma interface" I get the following error:

C:\DOCUME~1\sosi\LOCALS~1\Temp/cce2aaaa.o(.ctors+0x0) undefined
reference to `_GLOBAL__I_main'
C:\DOCUME~1\sosi\LOCALS~1\Temp/cce2aaaa.o(.dtors+0x0) undefined
reference to `_GLOBAL__D_main'

This occurs under the latest MinGW (MSYS rxvt shell) where

gcc -v
Reading specs from c:/MinGW/bin/../lib/gcc-lib/mingw32/3.2/specs
Configured with:
../gcc/configure --with-gcc --with-gnu-ld --with-gnu-as --host=mingw32 --tar
get=mingw32 --prefix=/mingw
 --enable-threads --disable-nls --enable-languages=f77,c++,objc,ada --disabl
e-win32-registry --disable-shared
Thread model: win32
gcc version 3.2 (mingw special 20020817-1)

And occurs under the latest CygWin using gcc 3.2

Reading specs from /usr/lib/gcc-lib/i686-pc-cygwin/3.2/specs
Configured with:
/netrel/src/gcc-3.2-1/configure --enable-languages=c,c++,f77,java --enable-l
ibgcj --enable-threads=posi
x --with-system-zlib --enable-nls --without-included-gettext --enable-interp
reter --disable-sjlj-exceptions --disable-ve
rsion-specific-runtime-libs --enable-shared --build=i686-pc-linux --host=i68
6-pc-cygwin --target=i686-pc-cygwin --enable
-haifa --prefix=/usr --exec-prefix=/usr --sysconfdir=/etc --libdir=/usr/lib 
--includedir=/nonexistent/include --libexecd
Thread model: posix
gcc version 3.2 20020818 (prerelease)

Can someone tell me what has changed with GCC-3.x that is causing this? Are
pragmas no longer supported? Does this have to do with template
instantiation? If so, how can I insure things are instantiated? Do I need
"external-templates" flag when I invoke the compiler? My project builds and
links fine under GCC-2.9.x just
fine, but I get many "undefined reference" errors when linking to its static
library when everything is compiled under GCC-3.2.x (also on Linux and

Any help appreciated,

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