[C++] "using namespace" in header file causes ambiguous reference

[lawben]

There is a using namespace FASTER::core; statement in file_common.h, which causes an ambiguous references in unrelated files.

I am including FASTER as a CMake submodule (via add_subdirectory) together with other third party projects. However, both FASTER and another implement their own Thread class. As there is a using namspace FASTER::core; statement in a FASTER header, somewhere down the (compile-) line, GCC sees two Thread classes.

I get the following error when compiling the other project's files.

error: reference to ‘Thread’ is ambiguous  <-- This is in the tls_thread.h file below
   59 | std::unordered_map<std::thread::id, Thread::TlsList *> Thread::registry_;

...

third_party/faster/cc/src/device/../core/thread.h:19:7: note: candidates are: ‘class FASTER::core::Thread’
   19 | class Thread {

... 

epoch_reclaimer-src/tls_thread.h:25:7: note: ‘class Thread’
   25 | class Thread : public std::thread {

By renaming FASTER's version to FasterThread, the problem is resolved. However, that is probably not the right solution. I suggest removing the using namespace statement from the header file, as recommended by Sutter, and namespace all entries within the header file correctly.

59. Don’t write namespace usings in a header file or before an #include

I'd be willing to create a PR for this, if you guys think this should be done.

[badrishc]

I see. Sure, pease go ahead with a PR for this. Thx.

[badrishc]

Just wanted to check on the status of this, thanks!

[lawben]

Sorry, I kinda forgot about this as I've been using a local workaround. I'll prepare the PR in the next few days.