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为什么 STL 代码似乎静态链接到 Darwin 上的 Boost 动态库？

当我在 OS X 上使用 gcc 4.6.1 和 toolset=darwin 构建 Boost 1.42/1.46.1/1.49 时，我发现生成的库静态包含大量 STL 代码，例如 std::basic_string<char> 和 std: :basic_string<wchar_t>。

在 OS X 10.6.8 上构建，我得到以下结果：

% otool -L /usr/local/boost-1.46.1/lib/libboost_system.dylib
boost-1.46.1/lib/libboost_system.dylib:
    libboost_system.dylib (compatibility version 0.0.0, current version 0.0.0)
    /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 125.2.11)
    /usr/local/lib/libgcc_s.1.dylib (compatibility version 1.0.0, current version 1.0.0)

根据'otool -L'输出，很明显 libstdc++ 没有与库动态链接。相比之下，在 Ubuntu 12.04 LTS 上，libboost_system.so 1.46.1 显示以下链接：

% ldd /usr/local/lib/libboost_system.so
    linux-vdso.so.1 =>  (0x00007fff495ff000)
    librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007fec4edb4000)
    libstdc++.so.6 => /usr/local/lib64/libstdc++.so.6 (0x00007fec4ea82000)
    libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007fec4e788000)
    libgcc_s.so.1 => /usr/local/lib64/libgcc_s.so.1 (0x00007fec4e573000)
    libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007fec4e355000)
    libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fec4df98000)
    /lib64/ld-linux-x86-64.so.2 (0x00007fec4f1e4000)

在这种情况下，libstdc++ 显然是动态链接的。在 OS X 方面，这就是我知道 STL 代码已直接包含在 Boost 库中的方式：

% nm -gfj /usr/local/boost-1.46.1/lib/libboost_system.dylib | c++filt --format=gnu-v3 | egrep "^std::basic_string"
std::basic_string<char, std::char_traits<char>, std::allocator<char> >::_M_disjunct(char const*) const
std::basic_string<char, std::char_traits<char>, std::allocator<char> >::find_last_of(char const*, unsigned long) const
std::basic_string<char, std::char_traits<char>, std::allocator<char> >::find_last_of(char const*, unsigned long, unsigned long) const
std::basic_string<char, std::char_traits<char>, std::allocator<char> >::find_last_of(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, unsigned long) const
std::basic_string<char, std::char_traits<char>, std::allocator<char> >::find_last_of(char, unsigned long) const
... [180 more lines] ...
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1 回答 1

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仅举一个例子： std::basic_string<char, std::char_traits<char>, std::allocator<char> >::find_last_of(char const*, unsigned long) const

std::basic_string is a template class, and does not exist in libstdc++.dylib. It was instantiated when the boost library was compiled, and (rightly) included there - because Boost.System uses it.

I suspect (but don't know) that this is true for all of the calls you see.

于 2012-06-22T21:51:38.870 回答