Re: Using --enable-debug and defining a macro from it...?

[Braden McDaniel]

Matthew Woehlke wrote:
> (If this isn't the place for 'how do I...?' questions, please re-direct 
> me, but I do see it isn't the -bugs list.)
>
> First off, I have a very skeleton configure.in (see below). How do I add 

The name "configure.ac" is preferred for autoconf >= 2.5x.

> '--enable-debug' to this? (I see AC_ARG_ENABLE, but is there not a 
> standard one for debug? I can't find one, but it seems to be a standard.)

There isn't and it's not. AC_ARG_ENABLE is what you would use for such 
an option.

Unless you have some unusual debugging requirements, I find that it's 
generally simpler to apply debugging-related options via the CPPFLAGS, 
CFLAGS, and CXXFLAGS user variables at configure time. Many useful 
debugging options will be compiler-specific.

> Second, I want to add a define to config.h based on the value of 
> --enable-debug. How do I do this?

You use AC_DEFINE to specify preprocessor definitions that will appear 
in your config header. Note that the config header is not intended to be 
installed; as such, using it to toggle things that impact your ABI is 
typically unwise.

> ====
> AC_INIT(<...>)
>
> AM_CONFIG_HEADER(config.h)
> AM_INIT_AUTOMAKE(<pkg>, 0.1)

Refer to the documention for a (at least somewhat) recent version of 
automake for the preferred form of AM_INIT_AUTOMAKE invocation.

> AC_LANG_CPLUSPLUS

This is unnecessary.

> AC_PROG_CC
> AC_PROG_CXX
> AC_PROG_RANLIB
> AC_PROG_INSTALL
>
> AC_OUTPUT(Makefile src/Makefile <...>)

The preferred way to do this with modern autoconf is to use 
AC_CONFIG_FILES and invoke AC_OUTPUT with no arguments.

Braden