automake: make the ARFLAGS default 'cr' instead of 'cru'.

In some GNU/Linux distributions people started to compile 'ar'
binary with --enable-deterministic-archives (binutils project).
That, however, in combination with our previous long time working
default AR_FLAGS=cru causes warnings on such installations:
ar: `u' modifier ignored since `D' is the default (see `U')

The 'u' option (at least with GNU binutils) did small optimization
during repeated builds because it instructed 'ar' to not
open/close unchanged *.o files and to rather read their contents
from old archive file.  However, its removal should not cause a
big performance hit for usual workflows.

Distributions started using --enable-deterministic-archives
knowing that it would disable the 'u', just to rather have a bit
more deterministic builds.

Also, to justify this change a bit more, keeping 'u' in ARFLAGS
could only result in many per-project changes to override
Automake's ARFLAGS default, just to silence such warnings.

Fixes bug#20082.  Reported by Eric Blake.

* bin/automake.in (handle_libraries): Use 'ARFLAGS=cr' by default.
* doc/automake.texi (Building a library): Mention the changed
ARFLAGS default.
(@c LocalWords): Replace 'cru' with 'cr'.
* m4/ar-lib.m4 (AM_PROG_AR): Cut out 'cru' string into separate
ARFLAGS variable with new default 'cr'.
* NEWS: Document.

diff --git a/NEWS b/NEWS
index d9c8640ff5197a751cd2d2b249d7adbd8f1efd7f..2a58785f326b1bb3b103177f4f6cd931d92184c4 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -10,6 +10,9 @@ New in 1.17:
   - AM_PATH_PYTHON will also search for Python versions 3.10 - 3.15.  It has
     previously searched for 3.0 - 3.9. (bug#53530)
 
+  - The default value of $ARFLAGS is now "cr" instead of "cru", to
+    support deterministic builds. (bug#20082)
+
   - RANLIB may be overridden on a per-target basis.
 
   - AM_TEXI2FLAGS may be defined to pass extra flags to TEXI2DVI & TEXI2PDF.
@@ -69,7 +72,7 @@ New in 1.17:
   - Pass any options given to AM_PROG_LEX on to AC_PROG_LEX.
     (bug#65600 and bug#65730)
 
-* Obsolescent features:
+* Obsolescence:
 
   - py-compile no longer supports Python 0.x or 1.x versions.  Python 2.0,
     released in 2000, is currently the minimum required version.

diff --git a/bin/automake.in b/bin/automake.in
index edc0488b8f50a7d9640db07757404964a521ba91..c0ffc198682c6c7b36a42ea9ce752796435dcaea 100644 (file)
--- a/bin/automake.in
+++ b/bin/automake.in
@@ -2674,7 +2674,7 @@ sub handle_libraries ()
     }
 
   define_variable ('AR', 'ar', INTERNAL);
-  define_variable ('ARFLAGS', 'cru', INTERNAL);
+  define_variable ('ARFLAGS', 'cr', INTERNAL);
   define_verbose_tagvar ('AR');
 
   foreach my $pair (@liblist)

diff --git a/doc/automake.texi b/doc/automake.texi
index 635bdd28c450e0ca1335cd1a8249b2ad6ac76316..af8dd836feba0636d865d98b76db8a8252772eb2 100644 (file)
--- a/doc/automake.texi
+++ b/doc/automake.texi
@@ -5181,7 +5181,7 @@ library and the list of objects, and finally by calling
 @code{RANLIB} (Automake will complain otherwise).  You should also
 call @code{AM_PROG_AR} to define @code{AR}, in order to support unusual
 archivers such as Microsoft lib.  @code{ARFLAGS} will default to
-@code{cru}; you can override this variable by setting it in your
+@code{cr}; you can override this variable by setting it in your
 @file{Makefile.am} or by @code{AC_SUBST}ing it from your
 @file{configure.ac}.  You can override the @code{AR} variable by
 defining a per-library @code{maude_AR} variable (@pxref{Program and
@@ -13625,7 +13625,7 @@ attach the @file{test-suite.log} file.
 @c  LocalWords:  Miller's installable includedir inc pkgdata EXEEXT libexec bsd
 @c  LocalWords:  pkglib libexecdir prog libcpio cpio's dlopen dlpreopen linux
 @c  LocalWords:  subsubsection OBJEXT esac lib LTLIBRARIES liblob LIBADD AR ar
-@c  LocalWords:  ARFLAGS cru ing maude libgettext lo LTLIBOBJS rpath SGI PRE yy
+@c  LocalWords:  ARFLAGS cr ing maude libgettext lo LTLIBOBJS rpath SGI PRE yy
 @c  LocalWords:  libmaude CCLD CXXFLAGS FFLAGS LFLAGS OBJCFLAGS RFLAGS DEFS cc
 @c  LocalWords:  OBJCXXFLAGS
 @c  LocalWords:  SHORTNAME vtable srcdir nostdinc basename yxx cxx ll lxx gdb

diff --git a/m4/ar-lib.m4 b/m4/ar-lib.m4
index f55b65019b8b5c10bb859850929991090eb6b216..e655b26f4d555943f301493e02ad945253739574 100644 (file)
--- a/m4/ar-lib.m4
+++ b/m4/ar-lib.m4
@@ -18,12 +18,13 @@ AC_REQUIRE([AM_AUX_DIR_EXPAND])dnl
 AC_REQUIRE_AUX_FILE([ar-lib])dnl
 AC_CHECK_TOOLS([AR], [ar lib "link -lib"], [false])
 : ${AR=ar}
+: ${ARFLAGS=cr}
 
 AC_CACHE_CHECK([the archiver ($AR) interface], [am_cv_ar_interface],
   [AC_LANG_PUSH([C])
    am_cv_ar_interface=ar
    AC_COMPILE_IFELSE([AC_LANG_SOURCE([[int some_variable = 0;]])],
-     [am_ar_try='$AR cru libconftest.a conftest.$ac_objext >&AS_MESSAGE_LOG_FD'
+     [am_ar_try='$AR $ARFLAGS libconftest.a conftest.$ac_objext >&AS_MESSAGE_LOG_FD'
       AC_TRY_EVAL([am_ar_try])
       if test "$ac_status" -eq 0; then
         am_cv_ar_interface=ar