Linker visibility issue

build.sh

clang++ -std=gnu++14 -stdlib=libc++ -Wno-deprecated-declarations -c test.cpp -o test.o -fvisibility=hidden
/usr/local/opt/llvm/bin/ld64.lld -dynamic -undefined dynamic_lookup -o test test.o
# Or:
# ld -dynamic -undefined dynamic_lookup -o test test.o -lSystem

Output

$ objdump -t test.o | grep 4soci7details11type_holder | c++filt
0000000000005090 gw    F __TEXT,__text	tm soci::details::type_holder<tm>::value<tm>() const
0000000000004500 gw    F __TEXT,__text	std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > soci::details::type_holder<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >::value<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >() const
0000000000000a40 gw    F __TEXT,__text	int soci::details::type_holder<int>::value<int>() const
0000000000005ac0 gw    O __DATA,__const	typeinfo for soci::details::type_holder<tm>
0000000000005a90 gw    O __DATA,__const	typeinfo for soci::details::type_holder<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >
00000000000058d8 gw    O __DATA,__const	typeinfo for soci::details::type_holder<int>
0000000000005886 gw    O __TEXT,__const	typeinfo name for soci::details::type_holder<tm>
00000000000057cc gw    O __TEXT,__const	typeinfo name for soci::details::type_holder<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >
00000000000056f4 gw    O __TEXT,__const	typeinfo name for soci::details::type_holder<int>

$ objdump -t test | grep 4soci7details11type_holder | c++filt
00000001000063ff lw    O __TEXT,__const	typeinfo name for soci::details::type_holder<tm>
00000001000071f8 lw    O __DATA,__const	typeinfo for soci::details::type_holder<tm>
0000000100005ce0 lw    F __TEXT,__text	tm soci::details::type_holder<tm>::value<tm>() const
0000000100005150 gw    F __TEXT,__text	std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > soci::details::type_holder<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >::value<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >() const
0000000100001690 gw    F __TEXT,__text	int soci::details::type_holder<int>::value<int>() const
00000001000071c8 gw    O __DATA,__const	typeinfo for soci::details::type_holder<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >
0000000100007010 gw    O __DATA,__const	typeinfo for soci::details::type_holder<int>
0000000100006345 gw    O __TEXT,__const	typeinfo name for soci::details::type_holder<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >
000000010000626d gw    O __TEXT,__const	typeinfo name for soci::details::type_holder<int>

^ How did the symbols for the struct tm specialization (and only those) end up marked as local in the output file?

test.cpp

#include <ctime>
#include <string>

#pragma GCC visibility push(default)
#include <soci/soci.h>
#pragma GCC visibility pop

using namespace std;
using namespace soci;

struct test_class
{
  int test_int;
  string test_string;
  tm test_tm;
};

namespace soci {
  template<> struct type_conversion<test_class>
  {
    typedef values base_type;
    static void from_base(values const &v, indicator ind, test_class &i);
  };
}

namespace soci {
  void type_conversion<test_class>::from_base(values const &v, indicator ind, test_class &i)
  {
    struct tm NullTm = {0};
    i.test_int = v.get<int>("test_int", -1);
    i.test_string = v.get<string>("test_string", "");
    i.test_tm = v.get<tm>("test_tm", NullTm);
  }
}