11 If you already have libc++ installed you can use it with clang.
15 $ clang++ -stdlib=libc++ test.cpp
16 $ clang++ -std=c++11 -stdlib=libc++ test.cpp
18 On OS X and FreeBSD libc++ is the default standard library
19 and the ``-stdlib=libc++`` is not required.
23 If you want to select an alternate installation of libc++ you
24 can use the following options.
28 $ clang++ -std=c++11 -stdlib=libc++ -nostdinc++ \
29 -I<libcxx-install-prefix>/include/c++/v1 \
30 -L<libcxx-install-prefix>/lib \
31 -Wl,-rpath,<libcxx-install-prefix>/lib \
34 The option ``-Wl,-rpath,<libcxx-install-prefix>/lib`` adds a runtime library
35 search path. Meaning that the systems dynamic linker will look for libc++ in
36 ``<libcxx-install-prefix>/lib`` whenever the program is run. Alternatively the
37 environment variable ``LD_LIBRARY_PATH`` (``DYLD_LIBRARY_PATH`` on OS X) can
38 be used to change the dynamic linkers search paths after a program is compiled.
40 An example of using ``LD_LIBRARY_PATH``:
44 $ clang++ -stdlib=libc++ -nostdinc++ \
45 -I<libcxx-install-prefix>/include/c++/v1
46 -L<libcxx-install-prefix>/lib \
48 $ ./a.out # Searches for libc++ in the systems library paths.
49 $ export LD_LIBRARY_PATH=<libcxx-install-prefix>/lib
50 $ ./a.out # Searches for libc++ along LD_LIBRARY_PATH
52 Using libc++experimental and ``<experimental/...>``
53 =====================================================
55 Libc++ provides implementations of experimental technical specifications
56 in a separate library, ``libc++experimental.a``. Users of ``<experimental/...>``
57 headers may be required to link ``-lc++experimental``.
61 $ clang++ -std=c++14 -stdlib=libc++ test.cpp -lc++experimental
63 Libc++experimental.a may not always be available, even when libc++ is already
64 installed. For information on building libc++experimental from source see
65 :ref:`Building Libc++ <build instructions>` and
66 :ref:`libc++experimental CMake Options <libc++experimental options>`.
68 Also see the `Experimental Library Implementation Status <http://libcxx.llvm.org/ts1z_status.html>`__
72 Experimental libraries are Experimental.
73 * The contents of the ``<experimental/...>`` headers and ``libc++experimental.a``
74 library will not remain compatible between versions.
75 * No guarantees of API or ABI stability are provided.
80 On Linux libc++ can typically be used with only '-stdlib=libc++'. However
81 some libc++ installations require the user manually link libc++abi themselves.
82 If you are running into linker errors when using libc++ try adding '-lc++abi'
83 to the link line. For example:
87 $ clang++ -stdlib=libc++ test.cpp -lc++ -lc++abi -lm -lc -lgcc_s -lgcc
89 Alternately, you could just add libc++abi to your libraries list, which in
90 most situations will give the same result:
94 $ clang++ -stdlib=libc++ test.cpp -lc++abi
100 GCC does not provide a way to switch from libstdc++ to libc++. You must manually
101 configure the compile and link commands.
103 In particular you must tell GCC to remove the libstdc++ include directories
104 using ``-nostdinc++`` and to not link libstdc++.so using ``-nodefaultlibs``.
106 Note that ``-nodefaultlibs`` removes all of the standard system libraries and
107 not just libstdc++ so they must be manually linked. For example:
111 $ g++ -nostdinc++ -I<libcxx-install-prefix>/include/c++/v1 \
112 test.cpp -nodefaultlibs -lc++ -lc++abi -lm -lc -lgcc_s -lgcc
115 GDB Pretty printers for libc++
116 ------------------------------
118 GDB does not support pretty-printing of libc++ symbols by default. Unfortunately
119 libc++ does not provide pretty-printers itself. However there are 3rd
120 party implementations available and although they are not officially
121 supported by libc++ they may be useful to users.
123 Known 3rd Party Implementations Include:
125 * `Koutheir's libc++ pretty-printers <https://github.com/koutheir/libcxx-pretty-printers>`_.
128 Libc++ Configuration Macros
129 ===========================
131 Libc++ provides a number of configuration macros which can be used to enable
132 or disable extended libc++ behavior, including enabling "debug mode" or
133 thread safety annotations.
136 See :ref:`using-debug-mode` for more information.
138 **_LIBCPP_ENABLE_THREAD_SAFETY_ANNOTATIONS**:
139 This macro is used to enable -Wthread-safety annotations on libc++'s
140 ``std::mutex`` and ``std::lock_guard``. By default these annotations are
141 disabled and must be manually enabled by the user.
143 **_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS**:
144 This macro is used to disable all visibility annotations inside libc++.
145 Defining this macro and then building libc++ with hidden visibility gives a
146 build of libc++ which does not export any symbols, which can be useful when
147 building statically for inclusion into another library.
149 **_LIBCPP_DISABLE_EXTERN_TEMPLATE**:
150 This macro is used to disable extern template declarations in the libc++
151 headers. The intended use case is for clients who wish to use the libc++
152 headers without taking a dependency on the libc++ library itself.
154 **_LIBCPP_ENABLE_TUPLE_IMPLICIT_REDUCED_ARITY_EXTENSION**:
155 This macro is used to re-enable an extension in `std::tuple` which allowed
156 it to be implicitly constructed from fewer initializers than contained
157 elements. Elements without an initializer are default constructed. For example:
161 std::tuple<std::string, int, std::error_code> foo() {
162 return {"hello world", 42}; // default constructs error_code
166 Since libc++ 4.0 this extension has been disabled by default. This macro
167 may be defined to re-enable it in order to support existing code that depends
168 on the extension. New use of this extension should be discouraged.
169 See `PR 27374 <http://llvm.org/PR27374>`_ for more information.
171 Note: The "reduced-arity-initialization" extension is still offered but only
172 for explicit conversions. Example:
177 using Tup = std::tuple<std::string, int, std::error_code>;
178 return Tup{"hello world", 42}; // explicit constructor called. OK.
181 **_LIBCPP_DISABLE_ADDITIONAL_DIAGNOSTICS**:
182 This macro disables the additional diagnostics generated by libc++ using the
183 `diagnose_if` attribute. These additional diagnostics include checks for:
185 * Giving `set`, `map`, `multiset`, `multimap` a comparator which is not
188 **_LIBCPP_NO_VCRUNTIME**:
189 Microsoft's C and C++ headers are fairly entangled, and some of their C++
190 headers are fairly hard to avoid. In particular, `vcruntime_new.h` gets pulled
191 in from a lot of other headers and provides definitions which clash with
192 libc++ headers, such as `nothrow_t` (note that `nothrow_t` is a struct, so
193 there's no way for libc++ to provide a compatible definition, since you can't
194 have multiple definitions).
196 By default, libc++ solves this problem by deferring to Microsoft's vcruntime
197 headers where needed. However, it may be undesirable to depend on vcruntime
198 headers, since they may not always be available in cross-compilation setups,
199 or they may clash with other headers. The `_LIBCPP_NO_VCRUNTIME` macro
200 prevents libc++ from depending on vcruntime headers. Consequently, it also
201 prevents libc++ headers from being interoperable with vcruntime headers (from
202 the aforementioned clashes), so users of this macro are promising to not
203 attempt to combine libc++ headers with the problematic vcruntime headers. This
204 macro also currently prevents certain `operator new`/`operator delete`
205 replacement scenarios from working, e.g. replacing `operator new` and
206 expecting a non-replaced `operator new[]` to call the replaced `operator new`.
208 C++17 Specific Configuration Macros
209 -----------------------------------
210 **_LIBCPP_ENABLE_CXX17_REMOVED_FEATURES**:
211 This macro is used to re-enable all the features removed in C++17. The effect
212 is equivalent to manually defining each macro listed below.
214 **_LIBCPP_ENABLE_CXX17_REMOVED_UNEXPECTED_FUNCTIONS**:
215 This macro is used to re-enable the `set_unexpected`, `get_unexpected`, and
216 `unexpected` functions, which were removed in C++17.
218 **_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR**:
219 This macro is used to re-enable `std::auto_ptr` in C++17.