Hello Ralf, On Fri, Mar 09, 2007 at 10:51:18AM +0100, Ralf Wildenhues wrote: > If they need an installable file that contains information generated by > configure, they could use a second config header with a manually written > template that contains only the minimal set of macros to be defined (and > those should all be package-specific, e.g., have a prefix like ACE_ or > so). > > Example: > AC_CONFIG_HEADERS(config.h ace_config.h) > > put this in ace_config.h.in: > > /* clients of the ACE library need to know whether this library was > compiled with features FOO and BAR */ > #undef ACE_FEATURE_FOO > #undef ACE_FEATURE_BAR I agree with this, but there is a trap, so let me go one step further: It is probable that the installable config header will be included by some other installable headers, say ace-beetles.h And it is usual that this public header is also used within the project itself, so the corresponding implementation file, say ace-1.2.3/beetles.c, includes ace-beetles.h. It also includes confog.h, of course. This implies that config.h and ace_config.h are sometimes used together. But since ACE_FEATURE_FOO et al. are sniffed out by autoheader, they get into config.h, too. Thus you get warnings from the compiler that ACE_FEATURE_FOO is being defined twice. I can see two ways to fix this: 1) one can fix ace-beetles.h and all similar files, so that they do not include ace_config.h when used within the ace pacakge. Disadvantage: the #ifdef's in the public headers might anoy users of ace-*.h. 2) Supposing that ace_config.h is guarded by symbol ACE_CONFIG_H, define that symbol in config.h, so that ace_config.h is then ignored. (config.h should be the first include in every *.c file, right?) The disadvantage is that the implementation might look a bit tricky. Here is how I did it in goffice/configure.ac: -----8<----- dnl This one is created by autoheader, ... AC_CONFIG_HEADERS(goffice/goffice-config.h) dnl ... and this one is a small subset, maintained manually, dnl which will be installed. AC_CONFIG_HEADERS(goffice/goffice-features.h) dnl dnl Make sure these two won't clash. Put the following to goffice-config.h: AH_BOTTOM([/* Don't include goffice-features.h, it's a subset of goffice-config.h. */ #define GOFFICE_FEATURES_H]) -----8<----- HTH, Stepan Kasal _______________________________________________ Autoconf mailing list Autoconf@xxxxxxx http://lists.gnu.org/mailman/listinfo/autoconf
