Language Choice

Packages that use both C and C++ need to test features of both compilers. Autoconf-generated configure scripts check for C features by default. The following macros determine which language's compiler is used in tests that follow in `configure.in'.

Macro: AC_LANG_C

Do compilation tests using CC and CPP and use extension `.c' for test programs.

Macro: AC_LANG_CPLUSPLUS

Do compilation tests using CXX and CXXCPP and use extension `.C' for test programs.

Macro: AC_LANG_SAVE

Remember the current language (as set by AC_LANG_C or AC_LANG_CPLUSPLUS) on a stack. Does not change which language is current. Use this macro and AC_LANG_RESTORE in macros that need to temporarily switch to a particular language.

Macro: AC_LANG_RESTORE

Select the language that is saved on the top of the stack, as set by AC_LANG_SAVE, and remove it from the stack. This macro is equivalent to either AC_LANG_C or AC_LANG_CPLUSPLUS, whichever had been run most recently when AC_LANG_SAVE was last called.

Do not call this macro more times than AC_LANG_SAVE.

Macro: AC_REQUIRE_CPP

Ensure that whichever preprocessor would currently be used for tests has been found. Calls AC_REQUIRE (see section Prerequisite Macros) with an argument of either AC_PROG_CPP or AC_PROG_CXXCPP, depending on which language is current.