Bob Friesenhahn wrote:
On Sun, 21 Dec 2003, Jeff Sheinberg wrote:
Paul Eggert writes: > Florian Weimer <fw@xxxxxxxxxxxxx> writes: > > > I'm writing a library that will require large-file support on 32-bit GNU ^^^^^^^^^^ > > platforms (so that off_t and ino_t are 64 bits wide, otherwise data > > structure layout would change). What is the canonical way to enforce > > this? > > AC_SYS_LARGEFILE
What about largefile support on a non-GNU system?
largefile support is _required_ according to unix98 specification (sus2), you will find it in all system claiming unix-compatibility.
Posix uses various "getconf" calls for compilation flags, library flags, and linking flags. The values returned from the various
forget about `getconf`, quick! ;-)=)
While it is true that Posix compliant systems should support "getconf", some systems do not. Regardless, my experience with AC_SYS_LARGEFILE on real-world systems is that it does produce the correct results.
The LFS standard specifies a set of -Defines that the system headers _will_ always react to. This is not just `from experience`, it is real paper standard in the unix98 documents. The macro AC_SYS_LARGEFILE will append these -Defines *if* it does notice them to have an effect on your platform. The standard way is "-D_FILE_OFFSET_BITS=64", and the macro checks also for a predecessor def used on AIX before LFS came about. This _will_ shift the off_t into a 64bit entity and reroute some calls to their *64 variants.
My configure script needs to have access to the values that AC_SYS_LARGEFILE sets since including config.h is not sufficient for all applications. Sometimes the options *must* be specified on the compiler command line to work. Therefore I augment AC_SYS_LARGEFILE as follows in order to define a LFS_CPPFLAGS variable which may be used within the Makefile:
Can you specify why? I am always interested in additional info that needs to be put at http://ac-archive.sf.net/largefile/ atleast for a warning. Some `gcc -include xx`? Some aix magic `-Llib64`?
Anyway, I recommend to _always_ use AC_SYS_LARGEFILE _and_ the special macro AC_FUNC_FSEEKO together - despite its innocent name, the latter macro adds again a magic -Define if needed, and that one is again specified int he LFS paper documents that had been included in the unix98 spec later on.
cheers, -- guido http://AC-Archive.sf.net GCS/E/S/P C++/++++$ ULHS L++w- N++@ s+:a d(+-) r+@>+++ y++ 5++X-
