Hi Matteo, > > * As you already noticed, we need to avoid build failures and runtime > > failures > > on platforms where this is not supported. > > > > I see "#ifdef __linux__" already in use in gnulibs, I assume this is > the preferred way.
Not really. When being compiled on an older Linux machine, that does not have the necessary include files, this "#ifdef __linux__" would lead to a compilation error. Therefore the preferred way is to test for the essential header files. For example, suppose AF_ALG gets defined by <linux/foobar.h> and is present in every version of <linux/foobar.h> (even the oldest ones). Then in the Autoconf macro we would need AC_CHECK_HEADERS([linux/foobar.h]) and in the code we would have #if HAVE_LINUX_FOOBAR_H > > * In the module description, section 'Include', you should not list all > > include > > files but only those that the user is supposed to include. In this case, > > I think, the af_alg business is invisible to the caller of the 4 > > modules. > > > > How to conditionally add files to lib_SOURCES depending on the system? > I guess that such code snippet is pasted somewhere in the Makefile, so > something like should work: > > lib_SOURCES += sha1.c > UNAME_S := $(shell uname -s) > ifeq ($(UNAME_S),Linux) > lib_SOURCES += af_alg.c > endif > > or do you have a better solution? This "solution" would not work when cross-compiling from Linux to non-Linux platforms or vice versa. It is better to rely only on the preprocessor defines, such as HAVE_LINUX_FOOBAR_H. It is perfectly OK to have a compilation unit that looks like this: #include <config.h> #include <unistd.h> /* or other general include files */ #if HAVE_LINUX_FOOBAR_H # include <linux/foobar.h> ... Here comes the actual code ... #endif In the worst case, this generates a .o file without any function definition. This is OK. (It generates a warning on AIX, IIRC, but that warning can be ignored.) Bruno
