configure: make --prefix=/usr and '' identical

  Ensure that all code that looks for an explicit --prefix=/usr
also checks for an implicit one.

Follow up to 81439a116cf48583127ddf1f09809440aa40969a
  

On Mon, 6 Jan 2025, DJ Delorie wrote:

> diff --git a/configure.ac b/configure.ac
> index 9af8d541e5..4934b044ce 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -2,6 +2,7 @@ dnl Process this file with autoconf to produce a configure script.
>  dnl Note we do not use AC_PREREQ here!  See aclocal.m4 for what we use instead.
>  AC_INIT([GNU C Library], [(see version.h)], [https://sourceware.org/bugzilla/],
>    [glibc], [https://www.gnu.org/software/glibc/])
> +AC_PREFIX_DEFAULT([/usr])

Does the AC_PREFIX_DEFAULT interface require such an autoconf-time 
constant at an early point in configure.ac?  (The proper default for Hurd 
is empty - no /usr - as used in build-many-glibcs.py.)

It looks like the previous commit regarding the default was missing a NEWS 
entry, and also an update to install.texi (+ INSTALL regeneration) to 
document the changed default.
  

Joseph Myers <josmyers@redhat.com> writes:
> Does the AC_PREFIX_DEFAULT interface require such an autoconf-time 
> constant at an early point in configure.ac?

The problem is that we pull in sysdeps config files from the most
specific to the generic, so setting --prefix in the linux config means
it won't be set in the linux/x86_64 config, which is where we set
libc_cv_complocaledir

If this is not acceptable, reverting my original patch makes more
sense.  It's just annoying to have to type --prefix=/usr ALL THE TIME.

> (The proper default for Hurd is empty - no /usr - as used in
> build-many-glibcs.py.)

The proper incantation for Hurd is --prefix= which still does the right
thing.  My change only affects if you omit --prefix= completely, which
previously did the wrong thing for Hurd too (defaulting to /usr/local)
  

Hi DJ, 

given that the original patch was not really a user-visible feature, just a "convenience
help" (that I fully agree with, I'd also happily omit --prefix=/usr), how about we revert
it now and put the full fix in after the release?

That automatically also gives the build code more "developer testing" then...

Cheers -a

Am Dienstag, 7. Januar 2025, 03:30:53 Mitteleuropäische Normalzeit schrieb DJ Delorie:
> 
> Ensure that all code that looks for an explicit --prefix=/usr
> also checks for an implicit one.
> 
> Follow up to 81439a116cf48583127ddf1f09809440aa40969a
> 
> diff --git a/aclocal.m4 b/aclocal.m4
> index e06366cdb2..61b328c21a 100644
> --- a/aclocal.m4
> +++ b/aclocal.m4
> @@ -311,7 +311,7 @@ dnl LIBC_SLIBDIR_RTLDDIR([slibdir], [rtlddir])
>  AC_DEFUN([LIBC_SLIBDIR_RTLDDIR],
>  [test -n "$libc_cv_slibdir" ||
>  case "$prefix" in
> -/usr | /usr/)
> +/usr | /usr/ | NONE)
>    libc_cv_slibdir='/$1'
>    libc_cv_rtlddir='/$2'
>    if test "$libdir" = '${exec_prefix}/lib'; then
> diff --git a/configure b/configure
> index b410ee4bd9..335cb80160 100755
> --- a/configure
> +++ b/configure
> @@ -608,6 +608,7 @@ PACKAGE_STRING='GNU C Library (see version.h)'
>  PACKAGE_BUGREPORT='https://sourceware.org/bugzilla/'
>  PACKAGE_URL='https://www.gnu.org/software/glibc/'
>  
> +ac_default_prefix=/usr
>  ac_unique_file="include/features.h"
>  enable_option_checking=no
>  ac_subst_vars='LTLIBOBJS
> @@ -2843,6 +2844,7 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
>  
>  
>  
> +
>  ac_config_headers="$ac_config_headers config.h"
>  
>  
> diff --git a/configure.ac b/configure.ac
> index 9af8d541e5..4934b044ce 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -2,6 +2,7 @@ dnl Process this file with autoconf to produce a configure script.
>  dnl Note we do not use AC_PREREQ here!  See aclocal.m4 for what we use instead.
>  AC_INIT([GNU C Library], [(see version.h)], [https://sourceware.org/bugzilla/],
>    [glibc], [https://www.gnu.org/software/glibc/])
> +AC_PREFIX_DEFAULT([/usr])
>  AC_CONFIG_SRCDIR([include/features.h])
>  AC_CONFIG_HEADERS([config.h])
>  AC_CONFIG_AUX_DIR([scripts])
> diff --git a/sysdeps/gnu/configure b/sysdeps/gnu/configure
> index 18c9d7945a..d16766bc70 100644
> --- a/sysdeps/gnu/configure
> +++ b/sysdeps/gnu/configure
> @@ -8,7 +8,7 @@
>  # in /lib and /etc.
>  test -n "$libc_cv_slibdir" ||
>  case "$prefix" in
> -/usr | /usr/)
> +/usr | /usr/ | NONE)
>    libc_cv_slibdir='/lib'
>    libc_cv_rtlddir='/lib'
>    if test "$libdir" = '${exec_prefix}/lib'; then
> @@ -19,7 +19,7 @@ case "$prefix" in
>    ;;
>  esac
>  case "$prefix" in
> -/usr | /usr/)
> +/usr | /usr/ | NONE)
>    # Allow the user to override the path with --sysconfdir.
>    if test "$sysconfdir" = '${prefix}/etc'; then
>      libc_cv_sysconfdir=/etc
> diff --git a/sysdeps/gnu/configure.ac b/sysdeps/gnu/configure.ac
> index 634fe4de2a..52bc35e223 100644
> --- a/sysdeps/gnu/configure.ac
> +++ b/sysdeps/gnu/configure.ac
> @@ -8,7 +8,7 @@ GLIBC_PROVIDES dnl See aclocal.m4 in the top level source directory.
>  # in /lib and /etc.
>  LIBC_SLIBDIR_RTLDDIR([lib], [lib])
>  case "$prefix" in
> -/usr | /usr/)
> +/usr | /usr/ | NONE)
>    # Allow the user to override the path with --sysconfdir.
>    if test "$sysconfdir" = '${prefix}/etc'; then
>      libc_cv_sysconfdir=/etc
> diff --git a/sysdeps/unix/sysv/linux/aarch64/configure b/sysdeps/unix/sysv/linux/aarch64/configure
> index b872b9870c..20669079ae 100644
> --- a/sysdeps/unix/sysv/linux/aarch64/configure
> +++ b/sysdeps/unix/sysv/linux/aarch64/configure
> @@ -5,7 +5,7 @@ arch_minimum_kernel=3.7.0
>  
>  test -n "$libc_cv_slibdir" ||
>  case "$prefix" in
> -/usr | /usr/)
> +/usr | /usr/ | NONE)
>    libc_cv_slibdir='/lib64'
>    libc_cv_rtlddir='/lib'
>    if test "$libdir" = '${exec_prefix}/lib'; then
> diff --git a/sysdeps/unix/sysv/linux/configure b/sysdeps/unix/sysv/linux/configure
> index 8cda8e9451..a23b55e82b 100644
> --- a/sysdeps/unix/sysv/linux/configure
> +++ b/sysdeps/unix/sysv/linux/configure
> @@ -1,4 +1,3 @@
> -ac_default_prefix=/usr
>  # This file is generated from configure.ac by Autoconf.  DO NOT EDIT!
>   # Local configure fragment for sysdeps/unix/sysv/linux.
>  
> @@ -117,8 +116,6 @@ if test -n "$sysheaders"; then
>    CPPFLAGS=$OLD_CPPFLAGS
>  fi
>  
> -
> -
>  if test "$prefix" = "/usr/local" -o "$prefix" = "/usr/local/"; then
>    if test $enable_sanity = yes; then
>      echo "\
> diff --git a/sysdeps/unix/sysv/linux/configure.ac b/sysdeps/unix/sysv/linux/configure.ac
> index 4c43cda877..6f224ed048 100644
> --- a/sysdeps/unix/sysv/linux/configure.ac
> +++ b/sysdeps/unix/sysv/linux/configure.ac
> @@ -71,8 +71,6 @@ if test -n "$sysheaders"; then
>    CPPFLAGS=$OLD_CPPFLAGS
>  fi
>  
> -AC_PREFIX_DEFAULT([/usr])
> -
>  if test "$prefix" = "/usr/local" -o "$prefix" = "/usr/local/"; then
>    if test $enable_sanity = yes; then
>      echo "\
> diff --git a/sysdeps/unix/sysv/linux/loongarch/configure b/sysdeps/unix/sysv/linux/loongarch/configure
> index 914943f914..0c9f2660d0 100644
> --- a/sysdeps/unix/sysv/linux/loongarch/configure
> +++ b/sysdeps/unix/sysv/linux/loongarch/configure
> @@ -196,7 +196,7 @@ case $libc_cv_loongarch_int_abi$libc_cv_loongarch_float_abi in
>  lp64s)
>    test -n "$libc_cv_slibdir" ||
>  case "$prefix" in
> -/usr | /usr/)
> +/usr | /usr/ | NONE)
>    libc_cv_slibdir='/lib64/sf'
>    libc_cv_rtlddir='/lib64'
>    if test "$libdir" = '${exec_prefix}/lib'; then
> @@ -210,7 +210,7 @@ esac
>  lp64d)
>    test -n "$libc_cv_slibdir" ||
>  case "$prefix" in
> -/usr | /usr/)
> +/usr | /usr/ | NONE)
>    libc_cv_slibdir='/lib64'
>    libc_cv_rtlddir='/lib64'
>    if test "$libdir" = '${exec_prefix}/lib'; then
> diff --git a/sysdeps/unix/sysv/linux/mips/configure b/sysdeps/unix/sysv/linux/mips/configure
> index 6e3402c111..93e0f5c8c6 100644
> --- a/sysdeps/unix/sysv/linux/mips/configure
> +++ b/sysdeps/unix/sysv/linux/mips/configure
> @@ -473,7 +473,7 @@ case $machine in
>  mips/mips64/n64/*)
>    test -n "$libc_cv_slibdir" ||
>  case "$prefix" in
> -/usr | /usr/)
> +/usr | /usr/ | NONE)
>    libc_cv_slibdir='/lib64'
>    libc_cv_rtlddir='/lib64'
>    if test "$libdir" = '${exec_prefix}/lib'; then
> @@ -487,7 +487,7 @@ esac
>  mips/mips64/n32/*)
>    test -n "$libc_cv_slibdir" ||
>  case "$prefix" in
> -/usr | /usr/)
> +/usr | /usr/ | NONE)
>    libc_cv_slibdir='/lib32'
>    libc_cv_rtlddir='/lib32'
>    if test "$libdir" = '${exec_prefix}/lib'; then
> diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/configure b/sysdeps/unix/sysv/linux/powerpc/powerpc64/configure
> index 5dd70689fc..42919b7880 100644
> --- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/configure
> +++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/configure
> @@ -3,7 +3,7 @@
>  
>  test -n "$libc_cv_slibdir" ||
>  case "$prefix" in
> -/usr | /usr/)
> +/usr | /usr/ | NONE)
>    libc_cv_slibdir='/lib64'
>    libc_cv_rtlddir='/lib64'
>    if test "$libdir" = '${exec_prefix}/lib'; then
> diff --git a/sysdeps/unix/sysv/linux/riscv/configure b/sysdeps/unix/sysv/linux/riscv/configure
> index 08aed0d805..3da51de84c 100755
> --- a/sysdeps/unix/sysv/linux/riscv/configure
> +++ b/sysdeps/unix/sysv/linux/riscv/configure
> @@ -212,7 +212,7 @@ case $libc_cv_riscv_int_abi$libc_cv_riscv_float_abi-$machine in
>  lp64-riscv/rv64/*)
>    test -n "$libc_cv_slibdir" ||
>  case "$prefix" in
> -/usr | /usr/)
> +/usr | /usr/ | NONE)
>    libc_cv_slibdir='/lib64/lp64'
>    libc_cv_rtlddir='/lib'
>    if test "$libdir" = '${exec_prefix}/lib'; then
> @@ -226,7 +226,7 @@ esac
>  lp64d-riscv/rv64/*)
>    test -n "$libc_cv_slibdir" ||
>  case "$prefix" in
> -/usr | /usr/)
> +/usr | /usr/ | NONE)
>    libc_cv_slibdir='/lib64/lp64d'
>    libc_cv_rtlddir='/lib'
>    if test "$libdir" = '${exec_prefix}/lib'; then
> @@ -240,7 +240,7 @@ esac
>  ilp32-riscv/rv32/*)
>    test -n "$libc_cv_slibdir" ||
>  case "$prefix" in
> -/usr | /usr/)
> +/usr | /usr/ | NONE)
>    libc_cv_slibdir='/lib32/ilp32'
>    libc_cv_rtlddir='/lib'
>    if test "$libdir" = '${exec_prefix}/lib'; then
> @@ -254,7 +254,7 @@ esac
>  ilp32d-riscv/rv32/*)
>    test -n "$libc_cv_slibdir" ||
>  case "$prefix" in
> -/usr | /usr/)
> +/usr | /usr/ | NONE)
>    libc_cv_slibdir='/lib32/ilp32d'
>    libc_cv_rtlddir='/lib'
>    if test "$libdir" = '${exec_prefix}/lib'; then
> diff --git a/sysdeps/unix/sysv/linux/s390/s390-64/configure b/sysdeps/unix/sysv/linux/s390/s390-64/configure
> index 5490bc669e..a858c8bc40 100644
> --- a/sysdeps/unix/sysv/linux/s390/s390-64/configure
> +++ b/sysdeps/unix/sysv/linux/s390/s390-64/configure
> @@ -3,7 +3,7 @@
>  
>  test -n "$libc_cv_slibdir" ||
>  case "$prefix" in
> -/usr | /usr/)
> +/usr | /usr/ | NONE)
>    libc_cv_slibdir='/lib64'
>    libc_cv_rtlddir='/lib'
>    if test "$libdir" = '${exec_prefix}/lib'; then
> diff --git a/sysdeps/unix/sysv/linux/sparc/sparc64/configure b/sysdeps/unix/sysv/linux/sparc/sparc64/configure
> index f09553588c..46c6c20256 100644
> --- a/sysdeps/unix/sysv/linux/sparc/sparc64/configure
> +++ b/sysdeps/unix/sysv/linux/sparc/sparc64/configure
> @@ -3,7 +3,7 @@
>  
>  test -n "$libc_cv_slibdir" ||
>  case "$prefix" in
> -/usr | /usr/)
> +/usr | /usr/ | NONE)
>    libc_cv_slibdir='/lib64'
>    libc_cv_rtlddir='/lib64'
>    if test "$libdir" = '${exec_prefix}/lib'; then
> diff --git a/sysdeps/unix/sysv/linux/x86_64/64/configure b/sysdeps/unix/sysv/linux/x86_64/64/configure
> index 2613d3af4f..73c8eb74de 100644
> --- a/sysdeps/unix/sysv/linux/x86_64/64/configure
> +++ b/sysdeps/unix/sysv/linux/x86_64/64/configure
> @@ -3,7 +3,7 @@
>  
>  test -n "$libc_cv_slibdir" ||
>  case "$prefix" in
> -/usr | /usr/)
> +/usr | /usr/ | NONE)
>    libc_cv_slibdir='/lib64'
>    libc_cv_rtlddir='/lib64'
>    if test "$libdir" = '${exec_prefix}/lib'; then
> diff --git a/sysdeps/unix/sysv/linux/x86_64/x32/configure b/sysdeps/unix/sysv/linux/x86_64/x32/configure
> index bf64c333e1..29073b569e 100644
> --- a/sysdeps/unix/sysv/linux/x86_64/x32/configure
> +++ b/sysdeps/unix/sysv/linux/x86_64/x32/configure
> @@ -5,7 +5,7 @@ arch_minimum_kernel=3.4.0
>  
>  test -n "$libc_cv_slibdir" ||
>  case "$prefix" in
> -/usr | /usr/)
> +/usr | /usr/ | NONE)
>    libc_cv_slibdir='/libx32'
>    libc_cv_rtlddir='/libx32'
>    if test "$libdir" = '${exec_prefix}/lib'; then
> 
>
  

On Tue, 7 Jan 2025, DJ Delorie wrote:

> Joseph Myers <josmyers@redhat.com> writes:
> > Does the AC_PREFIX_DEFAULT interface require such an autoconf-time 
> > constant at an early point in configure.ac?
> 
> The problem is that we pull in sysdeps config files from the most
> specific to the generic, so setting --prefix in the linux config means
> it won't be set in the linux/x86_64 config, which is where we set
> libc_cv_complocaledir

Maybe having sysdeps/unix/preconfigure.ac and sysdeps/hurd/preconfigure.ac 
that call AC_PREFIX_DEFAULT inside a suitable case condition on the host 
OS could work?  (Arguably the first should be 
sysdeps/unix/sysv/linux/preconfigure.ac, but then the preconfigure logic 
would need to change to look at preconfigure fragments in deeper 
subdirectories of sysdeps.)
  

On Jan 08 2025, Joseph Myers wrote:

> Maybe having sysdeps/unix/preconfigure.ac and sysdeps/hurd/preconfigure.ac 
> that call AC_PREFIX_DEFAULT inside a suitable case condition on the host 
> OS could work?

That cannot work.  AC_PREFIX_DEFAULT adds the assignment to the DEFAULTS
diversion, which is emitted by AC_INIT at the head of the generated
configure script.  That does not work for the sysdep configure
fragments, since they are processed independently and cannot contribute
to the main configure script.  Also, AC_PREFIX_DEFAULT cannot be used
conditionally.
  

"Andreas K. Huettel" <andreas.huettel@ur.de> writes:
> given that the original patch was not really a user-visible feature, just a "convenience
> help" (that I fully agree with, I'd also happily omit --prefix=/usr), how about we revert
> it now and put the full fix in after the release?

I have reverted the original patch.