File: autoconf.info,  Node: C++ Compiler,  Next: Objective C Compiler,  Prev: C Compiler,  Up: Compilers and Preprocessors

5.10.4 C++ Compiler Characteristics
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 -- Macro: AC_PROG_CXX ([COMPILER-SEARCH-LIST])
     Determine a C++ compiler to use.

     If either the environment variable ‘CXX’ or the environment
     variable ‘CCC’ is set, its value will be taken as the name of a C++
     compiler.  If both are set, ‘CXX’ is preferred.  If neither are
     set, search for a C++ compiler under a series of likely names,
     trying ‘g++’ and ‘c++’ first.  Regardless, the output variable
     ‘CXX’ is set to the chosen compiler.

     If the optional first argument to the macro is used, it must be a
     whitespace-separated list of potential names for a C++ compiler,
     which overrides the built-in list.

     If no C++ compiler can be found, as a last resort ‘CXX’ is set to
     ‘g++’ (and subsequent tests will probably fail).

     If the selected C++ compiler is found to be GNU C++ (regardless of
     its name), the shell variable ‘GXX’ will be set to ‘yes’.  If the
     shell variable ‘CXXFLAGS’ was not already set, it is set to ‘-g
     -O2’ for the GNU C++ compiler (‘-O2’ on systems where G++ does not
     accept ‘-g’), or ‘-g’ for other compilers.  ‘CXXFLAGS’ is then made
     an output variable.  You can override the default for ‘CXXFLAGS’ by
     inserting a shell default assignment between ‘AC_INIT’ and
     ‘AC_PROG_CXX’:

          : ${CXXFLAGS="OPTIONS"}

     where OPTIONS are the appropriate set of options to use by default.
     (It is important to use this construct rather than a normal
     assignment, so that ‘CXXFLAGS’ can still be overridden by the
     person building the package.  *Note Preset Output Variables::.)

     If necessary, options are added to ‘CXX’ to enable support for ISO
     Standard C++ features with extensions, preferring the newest
     edition of the C++ standard that is supported.  Currently the
     newest edition Autoconf knows how to detect support for is C++11.
     After calling this macro, you can check whether the C++ compiler
     has been set to accept standard C++ by inspecting the shell
     variable ‘ac_prog_cxx_stdcxx’.  Its value will be ‘cxx11’ or
     ‘cxx98’, respectively, if the C++ compiler has been set to use the
     2011 or 1990 edition of the C++ standard, and ‘no’ if the compiler
     does not support compiling standard C++ at all.

     The tests for standard conformance are not comprehensive.  They
     test the value of ‘__cplusplus’ and a representative sample of the
     language features added in each version of the C++ standard.  They
     do not test the C++ standard library, because this can be extremely
     slow, and because the C++ compiler might be generating code for a
     "freestanding environment" (in which most of the C++ standard
     library is optional).  If you need to know whether a particular C++
     standard header exists, use ‘AC_CHECK_HEADER’.

     None of the options that may be added to ‘CXX’ by this macro enable
     _strict_ conformance to the C++ standard.  In particular,
     system-specific extensions are not disabled.  (For example, for GNU
     C++, the ‘-std=gnu++NN’ options may be used, but not the
     ‘-std=c++NN’ options.)

 -- Macro: AC_PROG_CXXCPP
     Set output variable ‘CXXCPP’ to a command that runs the C++
     preprocessor.  If ‘$CXX -E’ doesn't work, tries ‘cpp’ and
     ‘/lib/cpp’, in that order.  Because of this fallback, ‘CXXCPP’ may
     or may not set C++-specific predefined macros (such as
     ‘__cplusplus’).

     It is portable to run ‘CXXCPP’ only on files with a ‘.c’, ‘.C’,
     ‘.cc’, or ‘.cpp’ extension.

     Some preprocessors don't indicate missing include files by the
     error status.  For such preprocessors an internal variable is set
     that causes other macros to check the standard error from the
     preprocessor and consider the test failed if any warnings have been
     reported.  However, it is not known whether such broken
     preprocessors exist for C++.

 -- Macro: AC_PROG_CXX_C_O
     Test whether the C++ compiler accepts the options ‘-c’ and ‘-o’
     simultaneously, and define ‘CXX_NO_MINUS_C_MINUS_O’, if it does
     not.