Re: problem with cached values

[Eric Blake]

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According to Vincent Torri on 12/26/2006 10:39 AM:
> 
> Hey,
> 
> I've written an m4 macro to check if stlport 5.1 is installed or not.
> The m4 file is attached.

> dnl
> dnl AM_CHECK_STLPORT(platform, prefix [, ACTION-IF-FOUND [, 
> ACTION-IF-NOT-FOUND]]])

You should not need to pass platform to the macro, as it is already
available as a shell variable.

> dnl Test for STLport 5.0 and define STLPORT_LIBS and STLPORT_CFLAGS.
> dnl
> AC_DEFUN([AM_CHECK_STLPORT],

The AM_* namespace is reserved for automake.  You should not reuse that
prefix, but invent one more appropriate for your package; perhaps
STL_CHECK_STLPORT.

>     dnl
>     dnl Get the name of the library with respect
>     dnl to the platform and the version of STLport.
>     dnl
>     case "$1" in
>        *bsd* | linux* | irix* | solaris* )

Gross.  Have you considered using libtool?  And even if you don't use
libtool, hard-coding platforms like this is not very portable, and
severely limits the utility of your macro.

>        ;;
>        [[cC]][[yY]][[gG]][[wW]][[iI]][[nN]]* | mingw32* | mks*)
>           if test x"${core_debug_mode}" = x"yes" ; then
>              if test x"${with_stlport_lib_debug_name_arg}" = x"yes" ; then
>                 STLPORT_LIB_NAME=${with_stlport_lib_name}
>              else
>                 STLPORT_LIB_NAME="libstlportg.5.1.a"

This only finds a static library, but cygwin supports shared libraries
(and in your case, you probably want to prefer the shared version).

>     dnl We check the headers, then the library.
>     stlport_lib_fullname=${stlport_libdir_path}/${STLPORT_LIB_NAME}
>     saved_CPPFLAGS="${CPPFLAGS}"
>     CPPFLAGS="${CPPFLAGS} -I${stlport_includedir_path}"
>     AC_CHECK_HEADERS(

Here's where your caching occurs.  Your nested invocation is remembering
the results of the outer invocation, because AC_CHECK_* is given the same
parameters between the two runs.  I'm not sure how I would improve things,
but you are right that calling your current macro in a nested manner runs
afoul of caching rules.

- --
Life is short - so eat dessert first!

Eric Blake             address@hidden
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