Remove add-ons mechanism

System Internals / glibc - Joseph Myers [] - 5 October 2017 11:58 EDT

glibc has an add-ons mechanism to allow additional software to be integrated into the glibc build. Such add-ons may be within the glibc source tree, or outside it at a path passed to the --enable-add-ons configure option.

localedata and crypt were once add-ons, distributed in separate release tarballs, but long since stopped using that mechanism. Linuxthreads was always an add-on. Ports spent some time as an add-on with separate release tarballs, then was first moved into the glibc source tree, then had its sysdeps files moved into the main sysdeps hierarchy so the add-ons mechanism was no longer used. NPTL spent some time as an add-on in the main glibc tree before stopping using the add-on mechanism. libidn used to have separate release tarballs but no longer does so, but still uses the add-ons mechanism within the glibc source tree. Various other software has supported building with the add-ons mechanism at times in the past, but I don't think any is still widely used.

Add-ons involve significant, little-used complexity in the glibc build system, and make it hard to understand what the space of possible glibc configurations is. This patch removes the add-ons mechanism. libidn is now built via the Subdirs mechanism to cause any configuration using sysdeps/unix/inet to build libidn; HAVE_LIBIDN (which effectively means shared libraries are available) is now defined via sysdeps/unix/inet/configure. Various references to add-ons around the source tree are removed (in the case of maint.texi, the example list of sysdeps directories is still very out of date).

Externally maintained ports should now put their files in the normal sysdeps directory structure rather than being arranged as add-ons; they probably need to change e.g. elf.h anyway, rather than actually being able to work just as a drop-in subtree. Hurd libpthread should be arranged similarly to NPTL, so some files might go in a hurd-pthreads (or similar) top-level directory in glibc, while sysdeps files should go in the normal sysdeps directory structure (possibly in hurd or hurd-pthreads subdirectories, just as there are nptl subdirectories in the sysdeps tree).

Tested for x86_64, and with

- (--enable-add-ons): Remove option. (machine): Do not mention add-ons in comment. (LIBC_PRECONFIGURE): Likewise. (add_ons): Remove variable and sanity checks and logic to locate add-ons. (add_ons_automatic): Remove variable. (configured_add_ons): Likewise. (add_ons_sfx): Likewise. (add_ons_pfx): Likewise. (add_on_subdirs): Likewise. (sysnames_add_ons): Likewise. Remove loop over add-ons and consideration of add-ons in Implies handling. (sysdeps_add_ons): Likewise.
- configure: Regenerated.
- libidn/ Remove.
- libidn/configure: Likewise.
- sysdeps/unix/inet/ New file.
- sysdeps/unix/inet/configure: New generated file.
- sysdeps/unix/inet/Subdirs: Add libidn.
- Makeconfig (sysdeps-srcdirs): Remove variable. (+sysdep_dirs): Do not include $(sysdeps-srcdirs). ($(common-objpfx)config.status): Do not depend on add-on files. ($(common-objpfx)shlib-versions.v.i): Do not mention add-ons in comment. (all-subdirs): Do not include $(add-on-subdirs).
- Makefile (dist-prepare): Do not use $(sysdeps-add-ons).
- (add-ons): Remove variable. (add-on-subdirs): Likewise. (sysdeps-add-ons): Likewise.
- manual/Makefile (add-chapters): Remove. ($(objpfx)texis): Do not depend on $(add-chapters). (nonexamples): Do not handle $(add-chapters). (examples): Do not handle $(add-ons). (chapters.% top-menu.%): Do not pass '$(add-chapters)' to
- manual/install.texi (Installation): Do not mention add-ons. (--enable-add-ons): Do not document configure option.
- INSTALL: Regenerated.
- manual/ Do not handle $2 add-ons argument.
- manual/maint.texi (Hierarchy Conventions): Do not mention add-ons.
- scripts/ (Glibc.build_glibc): Do not use
- scripts/gen-sorted.awk: Do not handle Subdirs files from add-ons.
- scripts/ Do not handle glibc-compat add-on.
- sysdeps/nptl/Makeconfig: Do not mention add-ons in comment.

644d385 Remove add-ons mechanism.
ChangeLog | 50 +++++
INSTALL | 17 --
Makeconfig | 27 +--
Makefile | 3 +-
NEWS | 4 + | 3 -
configure | 287 +++-------------------------- | 268 +++------------------------
libidn/configure | 16 --
manual/Makefile | 9 +-
manual/install.texi | 16 --
manual/ | 17 +-
manual/maint.texi | 11 +-
scripts/ | 1 -
scripts/gen-sorted.awk | 34 +---
scripts/ | 3 +-
sysdeps/nptl/Makeconfig | 2 +-
sysdeps/unix/inet/Subdirs | 1 +
sysdeps/unix/inet/configure | 9 +
{libidn => sysdeps/unix/inet}/ | 8 +-
20 files changed, 137 insertions(+), 649 deletions(-)


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