没有用于使用clang ++ 3.2初始化'vector <string>'的匹配构造函数

Question

我正在学习c ++与C++ Primer,第5版.

我正在尝试使用clang ++编译一个带有C++ 11特性的简单c ++程序,但是我得到了应该是有效代码的编译错误.

这是一个例子:

#include <iostream>
#include <vector>
#include <string>

using namespace std;

int main(){
  int n = 0;
  auto *p = &n; //<-- this compiles  

  cout << *p << endl;

  vector<string> articles = {"a", "an", "the"}; //<-- this fails; copied from the book

  return 0;
}

这是完整的错误:

$ clang++ -std=c++11 -v test.cpp -o test
clang version 3.2 (tags/RELEASE_32/final)
Target: x86_64-apple-darwin10.8.0
Thread model: posix
 "/usr/local/Cellar/llvm/3.2/bin/clang" -cc1 -triple x86_64-apple-macosx10.6.0 -emit-obj -mrelax-all -disable-free -main-file-name test.cpp -mrelocation-model pic -pic-level 2 -mdisable-fp-elim -masm-verbose -munwind-tables -target-cpu core2 -target-linker-version 127.2 -v -resource-dir /usr/local/Cellar/llvm/3.2/bin/../lib/clang/3.2 -fmodule-cache-path /var/folders/pk/pkIeYbRaF-yeeUH3Q6Q5AE+++TI/-Tmp-/clang-module-cache -std=c++11 -fdeprecated-macro -fdebug-compilation-dir /Users/Oton/Desktop -ferror-limit 19 -fmessage-length 150 -stack-protector 1 -mstackrealign -fblocks -fobjc-runtime=macosx-10.6.0 -fobjc-dispatch-method=mixed -fobjc-default-synthesize-properties -fencode-extended-block-signature -fcxx-exceptions -fexceptions -fdiagnostics-show-option -fcolor-diagnostics -o /var/folders/pk/pkIeYbRaF-yeeUH3Q6Q5AE+++TI/-Tmp-/test-w65CaF.o -x c++ test.cpp
clang -cc1 version 3.2 based upon LLVM 3.2svn default target x86_64-apple-darwin10.8.0
#include "..." search starts here:
#include <...> search starts here:
 /usr/include/c++/4.2.1
 /usr/include/c++/4.2.1/i686-apple-darwin10/x86_64
 /usr/include/c++/4.2.1/backward
 /usr/include/c++/4.0.0
 /usr/include/c++/4.0.0/i686-apple-darwin8
 /usr/include/c++/4.0.0/backward
 /usr/local/include
 /usr/local/Cellar/llvm/3.2/bin/../lib/clang/3.2/include
 /usr/include
 /System/Library/Frameworks (framework directory)
 /Library/Frameworks (framework directory)
End of search list.
test.cpp:13:18: error: no matching constructor for initialization of 'vector<string>'
  vector<string> articles = {"a", "an", "the"};
                 ^          ~~~~~~~~~~~~~~~~~~
/usr/include/c++/4.2.1/bits/stl_vector.h:255:9: note: candidate constructor [with _InputIterator = const char *] not viable: no known conversion from
      'const char [4]' to 'const allocator_type' (aka 'const std::allocator<std::basic_string<char> >') for 3rd argument
        vector(_InputIterator __first, _InputIterator __last,
        ^
/usr/include/c++/4.2.1/bits/stl_vector.h:213:7: note: candidate constructor not viable: no known conversion from 'const char [2]' to 'size_type'
      (aka 'unsigned long') for 1st argument
      vector(size_type __n, const value_type& __value = value_type(),
      ^
/usr/include/c++/4.2.1/bits/stl_vector.h:201:7: note: candidate constructor not viable: allows at most single argument '__a', but 3 arguments were
      provided
      vector(const allocator_type& __a = allocator_type())
      ^
/usr/include/c++/4.2.1/bits/stl_vector.h:231:7: note: candidate constructor not viable: requires single argument '__x', but 3 arguments were provided
      vector(const vector& __x)
      ^
1 error generated.

我在Mac上,10.6.8,我用自制的llvm/clang选项:

brew install llvm -v --all-targets --rtti --shared --with-asan --with-clang --use-clang

我究竟做错了什么？

Answer 1

该错误告诉您没有std :: vector构造函数采用初始化列表.问题是您使用的标准库实现尚未针对C++ 11进行更新.您使用的是libstdc ++的gcc 4.2版本,它是在C++ 11之前编写的.

您必须切换到已为C++ 11更新的库.如果您安装了libc ++,那么您可以只使用该标志-stdlib=libc++.我认为libc ++二进制文件是OS X 10.6.8的一部分,但你也需要头文件.也许自制软件有一个食谱,或者你可以从http://libcxx.llvm.org/下载它们并将它们粘贴在适当的位置,以便找到并与之一起使用-stdlib=libc++.

或者你可以手动省略普通的C++标准库头文件(本例中为gcc 4.2)-nostdinc++,手动添加一个include目录,无论你在哪里粘贴头文件,都可以为二进制文件添加库搜索目录(你甚至可以构建)二进制你自己)并添加链接标志-lc++.

Answer 2

我不确定这是不是很好,但我会回答我自己的问题.我希望这会有助于其他人.

(我只是一个初学者,所以如果我做错了,请纠正我.)

构建上述示例的唯一方法是:

-std=c++11 -stdlib=libc++ -nostdinc++ -I/path/to/new/libcxx/include

问题是Snow Leopard,正如其他人在这里所说的那样,它有一个非常古老的gcc版本.使用上面的选项无法链接因为ld: library not found for -lc++.

所以我不得不建立一个最新版本的libcxx.有一个macports端口,但没有自制的食谱.我是手动构建的,但有一些事情我不得不继续成功.

我假设你已经用自制软件安装了llvm并且你的路径设置正确:which clang++ -> /usr/local/bin/clang++.

首先得到libc ++ abi: svn co http://llvm.org/svn/llvm-project/libcxxabi/trunk libcxxabi

然后得到libc ++ : svn co http://llvm.org/svn/llvm-project/libcxx/trunk libcxx.

编辑libc++abi/lib/buildit:

EXTRA_FLAGS="...
             -I/usr/llvm-gcc-4.2/lib/gcc/i686-apple-darwin10/4.2.1/include \
             -I/PATH/TO/libcxx/include"
(Add the last two lines, note that the last include should point to the include folder inside libcxx from svn.)

LDSHARED_FLAGS="...-install_name /usr/local/lib/libc++abi.dylib"
(My libc++abi.dylib will reside inside /usr/local/lib.)

现在构建libc ++ abi:

- cd libc++abi/lib 
- export TRIPLE=-apple-
- ./buildit

我更喜欢用自制软件管理我的所有第三方库,所以这是可选的:

- mkdir -p /usr/local/Cellar/libc++abi/HEAD/lib
- mkdir -p /usr/local/Cellar/libc++abi/HEAD/include
- cp -a *.dylib /usr/local/Cellar/libc++abi/HEAD/lib/
- cp -R /path/to/libcxxabi/include/ /usr/local/Cellar/libc++abi/HEAD/include/libc++abi
  (Note the / after include!)
- brew link libc++abi

现在编辑libc++/lib/buildit:

if [ "$MACOSX_DEPLOYMENT_TARGET" == "10.6" ]
then
    EXTRA_FLAGS="... -I/usr/local/include/libc++abi"
    LDSHARED_FLAGS="...
        -install_name /usr/local/lib/libc++.1.dylib \
        ..."

现在构建libc ++:

- cd libc++abi/lib 
- export TRIPLE=-apple-
- export MACOSX_DEPLOYMENT_TARGET=10.6
- ./buildit

再次可选:

- mkdir -p /usr/local/Cellar/libc++/HEAD/lib
- cp -a *.dylib /usr/local/Cellar/libc++/HEAD/lib
- mkdir -p /usr/local/Cellar/libc++/HEAD/include
- cp -R /path/to/libcxx/include/ /usr/local/Cellar/libc++/HEAD/include/libc++
- brew link libc++

我现在可以用以下代码构建前面的示例:

clang++ -std=c++11 -stdlib=libc++ -nostdinc++ -I/usr/local/include/libc++ -O2 -g -v test.cpp -o test