* Bruno Haible: > Florian Weimer wrote: > >> 64-bit file offsets enabled real use cases. > > Year 2038 is also a real use-case. It is not so rare that machines are > being used for 15 years. (I still occasionally use a 14-years old > computer, and had a washing machine that lasted 25 years.) > Year 2038 is less than 17 years away. So, it is time to do something for > year 2038 now, not in five years.
Y2038 support requires recompilation. If you are able to do that, why not recompile for a 64-bit architecture? >> I assume GNU clisp (at least in a full build) need to link to some >> system libraries which are not dual ABI (and probably never will be). >> If gnulib forces the use of time64 mode, then it creates a push towards >> time64 mode in those libraries, too. At that point, these libraries >> will no longer be usable for running older binaries (in at least some >> cases; in others, the time_t symbols are not actually used). >> ... >> gnulib is pushing things in one particular direction, a >> direction ... > > Let me try to summarize your arguments, the way I understand them. > > 1) The ability to run older binaries is essential for nearly all > distros. > > 2) On i386, 32-bit time_t and 64-bit time_t are not binary compatible, > when used in the public API of a shared library. Assume an existing > old binary relies on /usr/lib/libfoo.so.5 and uses its API with > 32-bit time_t assumption. Then this library must stay in place with > the same API. > > 3) The distribution can provide a libfoo.so compiled with 64-bit > time_t, but it MUST reside in a different file. I think there is also the possibility of a dual ABI, see below. > Pieces that are missing, AFAICS, are: > > A) Possibly some glibc "magic" with shared library versioning would > make this situation simpler? Or is the combination of ldconfig and > LD_LIBRARY_PATH etc. sufficient? This probably needs per-package/component work to enable dual ABI, similar to what glibc did for its time_t interfaces. There is no linker magic involved, it's either symbol redirects (using a GCC extension) or a preprocessor macro. A dual ABI avoids the need for new soname and the introduction of symbol versioning (so that the object can be loaded twice into the same process with different ABIs). I don't expect many upstreams to support this effort. > B) A writeup for distributors, what is the recommended way to handle > the situation. > There are several _possible_ ways to handle it. But Linux distros > aim at being compatible at the binary level, and that requires > a _common_ approch among distros. IMO, the Linux Standard Base (LSB) > is the forum where such things should be standardized. > Have the LSB people already been involved in the discussion? LSB is quite dead, and it never covered the interesting packages anyway. I can see distributions building 32-bit Arm and a *new*, separate variant of i386 for 64-bit time_t, and the original i386 port remains at 32-bit. The new i386 port would have a glibc that defaults to 64-bit time_t. Two separate i386 ports seem to require the least human resources to maintain. If that's the chosen approach, gnulib should just use whatever the default time_t size is, and not attempt to override it. Thanks, Florian
