Hi, ucommon 7.0.0 fails to build on Mac OS X 10.7 and 10.8 with the version of Apple Clang provided by Xcode. The error is:
../inc/ucommon/platform.h:552:51: error: use of undeclared identifier 'nullptr' Here are full build logs: https://build.macports.org/builders/ports-10.7_x86_64_legacy-builder/builds/103277/steps/install-port/logs/stdio https://build.macports.org/builders/ports-10.8_x86_64_legacy-builder/builds/95334/steps/install-port/logs/stdio My understanding is that nullptr is a part of the C++11 standard. The default C++ standard library used on OS X 10.8 and earlier is the Apple GCC 4.2.1 version of libstdc++, and it does not support C++11. The default C++ standard library used on OS X 10.9 and later is libc++, and it does support C++11. Looking at platform.h, it appears to be going to some effort to support pre-C++11 platforms, so I think there may just be a mistake in how it's handling nullptr. The build succeeds on Mac OS X 10.6 using its Apple GCC 4.2.1 compiler. Apparently the build correctly detects that this platform doesn't support nullptr so it doesn't try to use it (or rather, it defines a compatibility implementation). It also succeeds on OS X 10.9 and later using its Apple clang compiler, where nullptr is supported. The condition used in platform.h to decide whether to define a compatibility implementation of nullptr is strange to me. It says: #if __cplusplus <= 199711L && !defined(_MSC_VER) #if ... ... #elif !defined(__clang__) || (defined(__clang__) && defined(__linux__)) This seems to suggest a belief that clang works differently on Linux than it does on other platforms, which is inaccurate. Clang does, however, work differently depending on whether the C++ standard library it is used with supports C++11 or not. And even when C++11 mode has not been requested, clang appears to support nullptr as an extension as long as the C++ standard library supports nullptr. So you need a different check than "defined(__linux__)" to determine if the compatibility nullptr is needed for clang, since it is also needed in some situations on macOS. For MacPorts, I have changed "defined(__linux__)" to "!defined(_LIBCPP_VERSION)" but I don't know if this is correct for other platforms. (On macOS, I know that only libc++ gives us C++11 support, but other platforms might use an updated version of libstdc++ containing C++11 support.) I have seen it suggested that __has_feature(cxx_nullptr) or __has_extension(cxx_nullptr) could be used, but I was not able to get that to work. In addition, I would like to draw your attention back to this previous bug report: http://lists.gnu.org/archive/html/bug-commoncpp/2017-10/msg00000.html The patch provided there still needs to be committed to your repository. We are using a similar patch in MacPorts. _______________________________________________ Bug-commoncpp mailing list Bug-commoncpp@gnu.org https://lists.gnu.org/mailman/listinfo/bug-commoncpp
