Clang compilation errors

[lisyarus]

Compiling with clang-3.3 results in following errors:

In file included from /home/niklis/work/rocksdb/rocksdb/port/port_posix.cc:10:
In file included from /home/niklis/work/rocksdb/rocksdb/./port/port_posix.h:38:
In file included from /usr/include/snappy.h:43:
In file included from /usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/string:40:
In file included from /usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/char_traits.h:39:
In file included from /usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/stl_algobase.h:64:
In file included from /usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/stl_pair.h:59:
In file included from /usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/move.h:57:
/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/type_traits:269:39: error: use of undeclared identifier '__float128'
    struct __is_floating_point_helper<__float128>

The same bug is reported here:
http://llvm.org/bugs/show_bug.cgi?id=13530

Changing -std=gnu++11 to -std=c++11 seems to fix it.

In file included from /home/niklis/work/rocksdb/rocksdb/util/statistics.cc:6:
In file included from /home/niklis/work/rocksdb/rocksdb/./util/statistics.h:7:
In file included from /home/niklis/work/rocksdb/rocksdb/include/rocksdb/statistics.h:13:
In file included from /usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/string:40:
In file included from /usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/char_traits.h:39:
/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/stl_algobase.h:739:11: error: overload resolution selected deleted operator '='
        *__first = __value;
        ~~~~~~~~ ^ ~~~~~~~
/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/stl_algobase.h:786:23: note: in instantiation of function template specialization 'std::__fill_n_a<std::__atomic_base<unsigned long> *,
      unsigned long, std::__atomic_base<unsigned long> >' requested here
      return _OI(std::__fill_n_a(std::__niter_base(__first), __n, __value));
                      ^
/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/stl_uninitialized.h:515:9: note: in instantiation of function template specialization 'std::fill_n<std::__atomic_base<unsigned long> *,
      unsigned long, std::__atomic_base<unsigned long> >' requested here
          std::fill_n(__first, __n, _ValueType());
               ^
/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/stl_uninitialized.h:544:2: note: in instantiation of function template specialization
      'std::__uninitialized_default_n_1<true>::__uninit_default_n<std::__atomic_base<unsigned long> *, unsigned long>' requested here
        __uninit_default_n(__first, __n);
        ^
/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/stl_uninitialized.h:605:12: note: in instantiation of function template specialization
      'std::__uninitialized_default_n<std::__atomic_base<unsigned long> *, unsigned long>' requested here
    { std::__uninitialized_default_n(__first, __n); }
           ^
/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/stl_vector.h:1224:7: note: in instantiation of function template specialization
      'std::__uninitialized_default_n_a<std::__atomic_base<unsigned long> *, unsigned long, std::__atomic_base<unsigned long> >' requested here
        std::__uninitialized_default_n_a(this->_M_impl._M_start, __n, 
             ^
/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/stl_vector.h:271:9: note: in instantiation of member function 'std::vector<std::__atomic_base<unsigned long>,
      std::allocator<std::__atomic_base<unsigned long> > >::_M_default_initialize' requested here
      { _M_default_initialize(__n); }
        ^
/home/niklis/work/rocksdb/rocksdb/util/statistics.cc:18:7: note: in instantiation of member function 'std::vector<std::__atomic_base<unsigned long>, std::allocator<std::__atomic_base<unsigned long> >
      >::vector' requested here
    : tickers_(TICKER_ENUM_MAX),
      ^
/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/atomic_base.h:360:22: note: candidate function has been explicitly deleted
      __atomic_base& operator=(const __atomic_base&) = delete;
                     ^
/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/atomic_base.h:361:22: note: candidate function has been explicitly deleted
      __atomic_base& operator=(const __atomic_base&) volatile = delete;
                     ^
/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/atomic_base.h:373:7: note: candidate function
      operator=(__int_type __i) noexcept
      ^
/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/atomic_base.h:380:7: note: candidate function
      operator=(__int_type __i) volatile noexcept

This seems to be a well-known bug in the c++ standard library:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58982

A workaround was found that fixes that and works in both gcc-4.8 and clang-3.3:

diff --git a/util/statistics.cc b/util/statistics.cc
index f86eb2c..53ea239 100644
--- a/util/statistics.cc
+++ b/util/statistics.cc
@@ -15,8 +15,7 @@ std::shared_ptr<Statistics> CreateDBStatistics() {
 }

 StatisticsImpl::StatisticsImpl()
-    : tickers_(TICKER_ENUM_MAX),
-      histograms_(HISTOGRAM_ENUM_MAX) {}
+    : histograms_(HISTOGRAM_ENUM_MAX) {}

 StatisticsImpl::~StatisticsImpl() {}

diff --git a/util/statistics.h b/util/statistics.h
index f598bdb..fa43c9e 100644
--- a/util/statistics.h
+++ b/util/statistics.h
@@ -10,6 +10,7 @@

 #include <vector>
 #include <atomic>
+#include <array>

 #define UNLIKELY(val) (__builtin_expect((val), 0))

@@ -28,7 +29,7 @@ class StatisticsImpl : public Statistics {
                              HistogramData* const data);

  private:
-  std::vector<std::atomic_uint_fast64_t> tickers_;
+  std::array<std::atomic_uint_fast64_t, TICKER_ENUM_MAX> tickers_;
   std::vector<HistogramImpl> histograms_;
 };

/home/niklis/work/rocksdb/rocksdb/db/table_properties_collector_test.cc:137:14: error: chosen constructor is explicit in copy-initialization
      return {};
             ^~
/usr/lib/gcc/x86_64-linux-gnu/4.8/../../../../include/c++/4.8/bits/unordered_map.h:138:7: note: constructor declared here
      unordered_map(size_type __n = 10,
      ^

This std::unordered_map constructor is declared explicit. A patch that makes this compile:

diff --git a/db/table_properties_collector_test.cc b/db/table_properties_collector_test.cc
index 6f405b2..cdc373e 100644
--- a/db/table_properties_collector_test.cc
+++ b/db/table_properties_collector_test.cc
@@ -134,7 +134,7 @@ class RegularKeysStartWithA: public TablePropertiesCollector {

   virtual TableProperties::UserCollectedProperties
     GetReadableProperties() const {
-      return {};
+      return TableProperties::UserCollectedProperties {};
   }

[igorcanadi]

(1) is fixed
(2) should already be fixed in the master branch. can you confirm?
(3) cc @liukai

[lisyarus]

Yes, 2nd case seems to be fixed in master.

[liukai]

I use clang 5.0 MacOS but didn't reproduce it (but I do saw that problem in some other platform).

I'll submit a diff to fix #3 soon.