如何在Makefile.am中指定要C ++ 0x? [英] How can I specify that I want C++0x in Makefile.am?

问题描述

目前，我的项目有以下简单的树:

Currently my project has the following simple tree:

./Makefile.am
./configure.ac
./README
./src/main.cpp
./src/Makefile.am
./bin

我正在尝试遵循以下教程:

I'm trying to following the following tutorial:

http://www.gnu.org/software/automake/manual/automake.html#Hello-World

如何指示configure.ac使用C ++ 0x扩展?特别是，如果main.cpp文件中的hello-world行如下所示:

How can I instruct configure.ac to use the C++0x extensions? In particular, what if the hello-world line in main.cpp file is as follows:

cout << ([] () {return "Hello, World!";}) () << endl;

发出"make"会导致错误.

Issuing "make" results in an error.

推荐答案

如果您正在使用gcc(看起来像您一样)，则可以从

If you're using gcc (looks like you are) then from the libstdc++ manual they have autoconf examples for checking c++ base language features:

# AC_COMPILE_STDCXX_OX
AC_DEFUN([AC_COMPILE_STDCXX_0X], [
  AC_CACHE_CHECK(if g++ supports C++0x features without additional flags,
  ac_cv_cxx_compile_cxx0x_native,
  [AC_LANG_SAVE
  AC_LANG_CPLUSPLUS
  AC_TRY_COMPILE([
  template <typename T>
    struct check
    {
      static_assert(sizeof(int) <= sizeof(T), "not big enough");
    };

    typedef check<check<bool>> right_angle_brackets;

    int a;
    decltype(a) b;

    typedef check<int> check_type;
    check_type c;
    check_type&& cr = c;],,
  ac_cv_cxx_compile_cxx0x_native=yes, ac_cv_cxx_compile_cxx0x_native=no)
  AC_LANG_RESTORE
  ])

  AC_CACHE_CHECK(if g++ supports C++0x features with -std=c++0x,
  ac_cv_cxx_compile_cxx0x_cxx,
  [AC_LANG_SAVE
  AC_LANG_CPLUSPLUS
  ac_save_CXXFLAGS="$CXXFLAGS"
  CXXFLAGS="$CXXFLAGS -std=c++0x"
  AC_TRY_COMPILE([
  template <typename T>
    struct check
    {
      static_assert(sizeof(int) <= sizeof(T), "not big enough");
    };

    typedef check<check<bool>> right_angle_brackets;

    int a;
    decltype(a) b;

    typedef check<int> check_type;
    check_type c;
    check_type&& cr = c;],,
  ac_cv_cxx_compile_cxx0x_cxx=yes, ac_cv_cxx_compile_cxx0x_cxx=no)
  CXXFLAGS="$ac_save_CXXFLAGS"
  AC_LANG_RESTORE
  ])

  AC_CACHE_CHECK(if g++ supports C++0x features with -std=gnu++0x,
  ac_cv_cxx_compile_cxx0x_gxx,
  [AC_LANG_SAVE
  AC_LANG_CPLUSPLUS
  ac_save_CXXFLAGS="$CXXFLAGS"
  CXXFLAGS="$CXXFLAGS -std=gnu++0x"
  AC_TRY_COMPILE([
  template <typename T>
    struct check
    {
      static_assert(sizeof(int) <= sizeof(T), "not big enough");
    };

    typedef check<check<bool>> right_angle_brackets;

    int a;
    decltype(a) b;

    typedef check<int> check_type;
    check_type c;
    check_type&& cr = c;],,
  ac_cv_cxx_compile_cxx0x_gxx=yes, ac_cv_cxx_compile_cxx0x_gxx=no)
  CXXFLAGS="$ac_save_CXXFLAGS"
  AC_LANG_RESTORE
  ])

  if test "$ac_cv_cxx_compile_cxx0x_native" = yes ||
     test "$ac_cv_cxx_compile_cxx0x_cxx" = yes ||
     test "$ac_cv_cxx_compile_cxx0x_gxx" = yes; then
    AC_DEFINE(HAVE_STDCXX_0X,,[Define if g++ supports C++0x features. ])
  fi
])

如果愿意，您可以尝试在其中放一个lambda.然后，在手握HAVE_STDCXX_0X的情况下，可以适当地设置--std = c ++ 0x.

You could probably try to put a lambda in there if you wanted. Then with HAVE_STDCXX_0X in hand you could set --std=c++0x appropriately.

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