https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89156
Bug ID: 89156
Summary: Templated member function has DEFAULT visibility
although instantiating class has not
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: gcc at martinien dot de
Target Milestone: ---
My understanding is this: When a templated class should get DEFAULT visibility,
the class itself and all the instantiating classes need to be marked with
__attribute__((visibility("default"))). gcc and clang behave that way.
However, they differ for templated member functions: gcc always exports
(probably using the visibility of the containing class), but clang follows the
rule above.
Example:
$ cat vis_test.cpp
#define EXPORT __attribute__((visibility("default")))
template<int a>
class ClassHidden
{
void func() {}
};
class EXPORT ClassWithTemplateFunction
{
template<typename T>
static void func() {}
};
template<class T>
class EXPORT ClassExported
{
void func() {}
};
template class ClassHidden<1>;
template void ClassWithTemplateFunction::func<ClassHidden<1>>();
template class ClassExported<ClassHidden<1>>;
$ cat test.sh
#!/bin/bash
echo
echo "gcc trunk:"
/h/tools/gcctrunk/bin/g++ -fvisibility=hidden -c vis_test.cpp -o vis_test_gcc.o
&& readelf -sW vis_test_gcc.o | c++filt | grep --color=never Class
echo
echo "clang trunk:"
/h/tools/llvmtrunk/bin/clang++ -fvisibility=hidden -c vis_test.cpp -o
vis_test_clang.o && readelf -sW vis_test_clang.o | c++filt | grep --color=never
Class
$ ./test.sh
gcc trunk:
14: 0000000000000000 11 FUNC WEAK HIDDEN 7
ClassHidden<1>::func()
15: 0000000000000000 7 FUNC WEAK DEFAULT 8 void
ClassWithTemplateFunction::func<ClassHidden<1> >()
16: 0000000000000000 11 FUNC WEAK HIDDEN 9
ClassExported<ClassHidden<1> >::func()
clang trunk:
5: 0000000000000000 10 FUNC WEAK HIDDEN 4
ClassHidden<1>::func()
6: 0000000000000000 10 FUNC WEAK HIDDEN 8
ClassExported<ClassHidden<1> >::func()
7: 0000000000000000 6 FUNC WEAK HIDDEN 6 void
ClassWithTemplateFunction::func<ClassHidden<1> >()
For ClassWithTemplateFunction::func<ClassHidden<1> >(), gcc emits DEFAULT
visibility.
Who is right, and why? :)
Best regards,
Martin
--
www.productive-cpp.com
