geirg71 commented on issue #177:
URL:
https://github.com/apache/logging-log4cxx/issues/177#issuecomment-1383078063
Thank you for the lightning fast response Stephen. Your 2 commits fix my
problem on MSYS2.
I do however ask you to look at the use of the
LOG4CXX_INSTANTIATE_EXPORTED_PTR macro. Clang 14 on Linux complains about the
same issue as GCC if I change the macro to the Windows variant (refer output
below). Hence I guess the C++ standard really prohibits this type of template
instantiations, and the issue could resurface later in e.g. future MSVC
versions implementing the standard.
For me both compilers are happy if I move LOG4CXX_INSTANTIATE_EXPORTED_PTR
outside of the log4cxx namespace. Example from propertysetter.h, change:
```
#include <log4cxx/logstring.h>
#include <log4cxx/helpers/object.h>
namespace log4cxx
{
namespace helpers
{
class Object;
// Instantiate template pointer type passed as parameter
LOG4CXX_INSTANTIATE_EXPORTED_PTR(Object);
LOG4CXX_PTR_DEF(Object);
```
to
```
#include <log4cxx/logstring.h>
#include <log4cxx/helpers/object.h>
// Instantiate template pointer type passed as parameter
LOG4CXX_INSTANTIATE_EXPORTED_PTR(log4cxx::helpers::Object);
namespace log4cxx
{
namespace helpers
{
class Object;
LOG4CXX_PTR_DEF(Object);
```
Clang 14 on Ubuntu 22.04 with #define LOG4CXX_INSTANTIATE_EXPORTED_PTR(T)
template class LOG4CXX_EXPORT std::shared_ptr<T>:
```
$ clang++ --version
Ubuntu clang version 14.0.0-1ubuntu1
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
[build] /usr/bin/clang++ -Ilogging-log4cxx/src/test/cpp/util
-Ilogging-log4cxx/build/src/main/include -Ilogging-log4cxx/src/main/include
-I/usr/include/apr-1.0 -g -std=c++17 -MD -MT
src/test/cpp/util/CMakeFiles/testingUtilities.dir/compare.cpp.o -MF
src/test/cpp/util/CMakeFiles/testingUtilities.dir/compare.cpp.o.d -o
src/test/cpp/util/CMakeFiles/testingUtilities.dir/compare.cpp.o -c
logging-log4cxx/src/test/cpp/util/compare.cpp
[build] In file included from
logging-log4cxx/src/test/cpp/util/compare.cpp:23:
[build]
logging-log4cxx/src/main/include/log4cxx/helpers/inputstreamreader.h:32:1:
error: explicit instantiation of 'shared_ptr' not in a namespace enclosing 'std'
[build] LOG4CXX_INSTANTIATE_EXPORTED_PTR(InputStream);
[build] ^
[build] logging-log4cxx/build/src/main/include/log4cxx/log4cxx.h:94:80:
note: expanded from macro 'LOG4CXX_INSTANTIATE_EXPORTED_PTR'
[build] #define LOG4CXX_INSTANTIATE_EXPORTED_PTR(T) template class
LOG4CXX_EXPORT std::shared_ptr<T>
[build]
^
[build]
/usr/bin/../lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/shared_ptr.h:175:11:
note: explicit instantiation refers here
[build] class shared_ptr : public __shared_ptr<_Tp>
```
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