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6.1 Language Choice
Autoconf-generated configure scripts check for the C compiler and
its features by default. Packages that use other programming languages
(maybe more than one, e.g., C and C++) need to test features of the
compilers for the respective languages. The following macros determine
which programming language is used in the subsequent tests in
configure.ac.
— Macro: AC_LANG ( language)
Do compilation tests using the compiler, preprocessor, and file
extensions for the specified language.
Supported languages are:
- ‘C’
- Do compilation tests using
CC and CPP and use extension
.c for test programs. Use compilation flags: CPPFLAGS with
CPP, and both CPPFLAGS and CFLAGS with CC.
- ‘C++’
- Do compilation tests using
CXX and CXXCPP and use
extension .C for test programs. Use compilation flags:
CPPFLAGS with CXXPP, and both CPPFLAGS and
CXXFLAGS with CXX.
- ‘Fortran 77’
- Do compilation tests using
F77 and use extension .f for
test programs. Use compilation flags: FFLAGS.
- ‘Fortran’
- Do compilation tests using
FC and use extension .f (or
whatever has been set by AC_FC_SRCEXT) for test programs. Use
compilation flags: FCFLAGS.
- ‘Erlang’
- Compile and execute tests using
ERLC and ERL and use extension
.erl for test Erlang modules. Use compilation flags: ERLCFLAGS.
- ‘Objective C’
- Do compilation tests using
OBJC and OBJCCPP and use
extension .m for test programs. Use compilation flags:
CPPFLAGS with OBJCPP, and both CPPFLAGS and
OBJCFLAGS with OBJC.
— Macro: AC_LANG_PUSH ( language)
Remember the current language (as set by AC_LANG) on a stack, and
then select the language. Use this macro and AC_LANG_POP
in macros that need to temporarily switch to a particular language.
— Macro: AC_LANG_POP ( [language])
Select the language that is saved on the top of the stack, as set by
AC_LANG_PUSH, and remove it from the stack.
If given, language specifies the language we just quit. It
is a good idea to specify it when it's known (which should be the
case...), since Autoconf detects inconsistencies.
AC_LANG_PUSH([Fortran 77])
# Perform some tests on Fortran 77.
# ...
AC_LANG_POP([Fortran 77])
— Macro: AC_LANG_ASSERT ( language)
Check statically that the current language is
language. You should use this in your language specific macros
to avoid that they be called with an inappropriate language.
This macro runs only at autoconf time, and incurs no cost at
configure time. Sadly enough and because Autoconf is a two
layer language 2, the macros
AC_LANG_PUSH and AC_LANG_POP cannot be “optimizing”,
therefore as much as possible you ought to avoid using them to wrap
your code, rather, require from the user to run the macro with a
correct current language, and check it with AC_LANG_ASSERT.
And anyway, that may help the user understand she is running a Fortran
macro while expecting a result about her Fortran 77 compiler...
— Macro: AC_REQUIRE_CPP
Ensure that whichever preprocessor would currently be used for tests has
been found. Calls AC_REQUIRE (see Prerequisite Macros) with an
argument of either AC_PROG_CPP or AC_PROG_CXXCPP,
depending on which language is current.
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