[Bug plugins/54069] New: linkage type of plugin API wrong

["weinert at gns-mbh dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54069

             Bug #: 54069
           Summary: linkage type of plugin API wrong
    Classification: Unclassified
           Product: gcc
           Version: 4.7.1
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: plugins
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: weinert@gns-mbh.com


Created attachment 27856
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27856
plugin source

gcc 4.7.0 and 4.7.1
created with:
./configure --prefix=/usr/local --program-suffix=-4.7.1 --with-mpc=/usr/local
--with-mpfr=/usr/local --with-gmp=/usr/local --enable-serial-configure
--enable-languages=c,c++,fortran,objc,obj-c++

plugin (see attached source) compiled with:
gcc-4.7.1 -I`gcc -print-file-name=plugin`/include -fPIC -shared -O2 plugin.c -o
plugin.so

try to use with:
gcc-4.7.1 -fplugin=./plugin.so test.c

where test.c is simply:
int main(int argc, char *argv[]) { return 0; }
or may be any other source, doesn't matter, the test plugin does nothing...

generates following error lines:

cc1: error: cannot load plugin ./plugin.so
./plugin.so: undefined symbol: list_length

Looking at the generated compiler (libgcc, gcc-executable, etc.) it seems that
presumably all functions from tree.h, input.h, and many others seem to have
C++-linkage though they are part of a C-API. Using
#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */
.... declarations ....
#ifdef __cplusplus
} /* extern "C" */
#endif /* __cplusplus */

in those headers cures the problem (after long recompile)...
the function used in the plugin is only example, there are tons(!!) of others
there that have the same problem..
it would be great if you could restore ability to use C for the plugin-API..
thanks...