problem with cached values

[Vincent Torri]

Hey,

I've written an m4 macro to check if stlport 5.1 is installed or not. The 
m4 file is attached.

I use that macro in that way:

AM_CHECK_STLPORT(
   [${target_os}],
   [/usr],
   [],
   [AM_CHECK_STLPORT(
      [${target_os}],
      [/usr/local],
      [],
      [AC_MSG_ERROR("STLport is needed !")])
   ])

that is, I want to autodetect STLport 5.1 in /usr or /usr/local.

I've installed STLport 5.1 in /usr/local. So, the first check (in /usr) 
returns a warning, and then STLport is searched in /usr/local. The result 
of the configure script is the following:

checking stl/config/user_config.h usability... no
checking stl/config/user_config.h presence... no
checking for stl/config/user_config.h... no
configure: WARNING: STLport headers not in /usr/include/stlport
checking for stl/config/user_config.h... (cached) no
configure: WARNING: STLport headers not in /usr/local/include/stlport
configure: error: "STLport is needed !"

If I force the check in /usr/local (with --with-stlport-path=/usr/local), 
there is no problem.

Can someone explain what the problem is, and then what kind of solution 
there is to such problem ?

Thank you

Vincent Torri

stlport.m4
Description: Text document