[Bug libgcc/63801] New: error: templates must have C++ linkage

[Bug libgcc/63801] New: error: templates must have C++ linkage

[gcc at ryandesign dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63801

            Bug ID: 63801
           Summary: error: templates must have C++ linkage
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libgcc
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gcc at ryandesign dot com

Hello, I'm a developer with the MacPorts project. I'm not the maintainer of our
gcc ports, but I am the one who created our gcc5 port and kept it updated until
version 5-20140824. No later snapshot of gcc5 has successfully built for me on
OS X, failing instead with the following message:


ccache /usr/bin/clang++ -arch x86_64 -c   -g  -DIN_GCC    -fno-exceptions
-fno-rtti -fasynchronous-unwind-tables -W -Wall -Wno-narrowing -Wwrite-strings
-Wcast-qual -Wno-format -Wmissing-format-attribute -Woverloaded-virtual
-pedantic -Wno-long-long -Wno-variadic-macros -Wno-overlength-strings
-fno-common  -DHAVE_CONFIG_H -I. -I.
-I/opt/local/var/macports/build/_Users_rschmidt_macports_dports_lang_gcc5/libgcc-devel/work/gcc-5-20141109/gcc
-I/opt/local/var/macports/build/_Users_rschmidt_macports_dports_lang_gcc5/libgcc-devel/work/gcc-5-20141109/gcc/.
-I/opt/local/var/macports/build/_Users_rschmidt_macports_dports_lang_gcc5/libgcc-devel/work/gcc-5-20141109/gcc/../include
-I/opt/local/var/macports/build/_Users_rschmidt_macports_dports_lang_gcc5/libgcc-devel/work/gcc-5-20141109/gcc/../libcpp/include
-I/opt/local/include -I/opt/local/include -I/opt/local/include 
-I/opt/local/var/macports/build/_Users_rschmidt_macports_dports_lang_gcc5/libgcc-devel/work/gcc-5-20141109/gcc/../libdecnumber
-I/opt/local/var/macports/build/_Users_rschmidt_macports_dports_lang_gcc5/libgcc-devel/work/gcc-5-20141109/gcc/../libdecnumber/dpd
-I../libdecnumber
-I/opt/local/var/macports/build/_Users_rschmidt_macports_dports_lang_gcc5/libgcc-devel/work/gcc-5-20141109/gcc/../libbacktrace
-DCLOOG_INT_GMP -I/opt/local/include -DCLOOG_INT_GMP  -I/opt/local/include -o
graphite-clast-to-gimple.o -MT graphite-clast-to-gimple.o -MMD -MP -MF
./.deps/graphite-clast-to-gimple.TPo
/opt/local/var/macports/build/_Users_rschmidt_macports_dports_lang_gcc5/libgcc-devel/work/gcc-5-20141109/gcc/graphite-clast-to-gimple.c
clang: warning: treating 'c' input as 'c++' when in C++ mode, this behavior is
deprecated
clang: warning: treating 'cpp-output' input as 'c++-cpp-output' when in C++
mode, this behavior is deprecated
In file included from
/opt/local/var/macports/build/_Users_rschmidt_macports_dports_lang_gcc5/libgcc-devel/work/gcc-5-20141109/gcc/graphite-clast-to-gimple.c:36:
In file included from /opt/local/include/isl/val_gmp.h:4:
In file included from /opt/local/include/gmp.h:34:
In file included from
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/iosfwd:89:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/__config:494:1:
error: templates must have C++ linkage
template <bool> struct __static_assert_test;
^~~~~~~~~~~~~~~
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/__config:495:20:
error: explicit specialization of non-template struct '__static_assert_test'
template <> struct __static_assert_test<true> {};
                   ^                   ~~~~~~
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/__config:496:1:
error: templates must have C++ linkage
template <unsigned> struct __static_assert_check {};
^~~~~~~~~~~~~~~~~~~


We are using gmp version 6.0.0 and isl version 0.14.

This was with the following OS X, Xcode and clang versions, but similar failure
occurs on earlier versions:


$ sw_vers
ProductName:    Mac OS X
ProductVersion:    10.10.1
BuildVersion:    14B17
$ xcodebuild -version
Xcode 6.1
Build version 6A1052d
$ clang -v
Apple LLVM version 6.0 (clang-600.0.54) (based on LLVM 3.5svn)
Target: x86_64-apple-darwin14.0.0
Thread model: posix
$

[Bug middle-end/63801] error: templates must have C++ linkage when building with isl and clang

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63801

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|libgcc                      |middle-end
            Summary|error: templates must have  |error: templates must have
                   |C++ linkage                 |C++ linkage when building
                   |                            |with isl and clang

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
This might be a bug in isl/gmp where it does an extern "C" around some include
files.

[Bug middle-end/63801] error: templates must have C++ linkage when building with isl and clang

[gcc at ryandesign dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63801

--- Comment #2 from Ryan Schmidt <gcc at ryandesign dot com> ---
Isn't the extern "C" coming from lines 32-38 of gcc/graphite-clast-to-gimple.c
which in version 5-20141109 say:


#if defined(__cplusplus)
extern "C" {
#endif
#include <isl/val_gmp.h>
#if defined(__cplusplus)
}
#endif


The first 4 lines of /opt/local/include/isl/val_gmp.h are simply:


#ifndef ISL_VAL_GMP_H
#define ISL_VAL_GMP_H

#include <gmp.h>


Lines 31-36 of /opt/local/include/gmp.h (the first non-comment lines) are:


#ifndef __GMP_H__

#if defined (__cplusplus)
#include <iosfwd>   /* for std::istream, std::ostream, std::string */
#include <cstdio>
#endif

[Bug middle-end/63801] error: templates must have C++ linkage when building with isl and clang

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63801

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |build

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
https://gcc.gnu.org/ml/gcc-patches/2014-02/msg00558.html


Looks like it was needed at one point because a bug in isl headers.  But this
might have been fixed already

[Bug middle-end/63801] error: templates must have C++ linkage when building with isl and clang

[gcc at ryandesign dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63801

--- Comment #4 from Ryan Schmidt <gcc at ryandesign dot com> ---
Thanks. If I remove the extern "C" then it fails with:


/opt/local/var/macports/build/_Users_rschmidt_macports_dports_lang_gcc5/libgcc-devel/work/gcc-5-20141109/gcc/graphite-optimize-isl.c:357:12:
error: use of undeclared identifier 'isl_band_member_is_zero_distance'
       if (isl_band_member_is_zero_distance (Band, i))
           ^


The isl changelog, under the heading "Changes since isl-0.12", says "The
function isl_band_member_is_zero_distance has been removed. Essentially the
same functionality is available through isl_band_member_is_coincident, except
that is requires setting up coincidence constraints. The option
schedule_outer_zero_distance has accordingly been replaced by the option
schedule_outer_coincidence."

[Bug middle-end/63801] error: templates must have C++ linkage when building with isl and clang

[gcc at ryandesign dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63801

--- Comment #5 from Ryan Schmidt <gcc at ryandesign dot com> ---
I see a patch for this has been provided on the mailing list:

https://www.mail-archive.com/gcc-patches@gcc.gnu.org/msg95468.html

It is a long thread and I haven't read all of it.

[Bug middle-end/63801] error: templates must have C++ linkage when building with isl and clang

[gcc at ryandesign dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63801

Ryan Schmidt <gcc at ryandesign dot com> changed:

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

--- Comment #6 from Ryan Schmidt <gcc at ryandesign dot com> ---
I see that with version 5-20141207 this patch is no longer needed, so I guess
the problem is fixed.