[automake-commit] branch master updated: test: check that subsecond mtime works with make.

[Karl Berry]

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karl pushed a commit to branch master
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View the commit online:
https://git.savannah.gnu.org/gitweb/?p=automake.git;a=commitdiff;h=23e69f6e6d29b0f9aa5aa3aab2464b3cf38a59bf

The following commit(s) were added to refs/heads/master by this push:
     new 23e69f6e6 test: check that subsecond mtime works with make.
23e69f6e6 is described below

commit 23e69f6e6d29b0f9aa5aa3aab2464b3cf38a59bf
Author: Karl Berry <karl@freefriends.org>
AuthorDate: Mon May 27 12:34:35 2024 -0700

    test: check that subsecond mtime works with make.
    
    Trying to fix https://bugs.gnu.org/68808.
    
    * m4/sanity.m4 (_AM_FILESYSTEM_TIMESTAMP_RESOLUTION): check
    that make works with subsecond mtimes, as well as sleep and ls.
    (Known to fail with the make 3.81 that ships with macOS.)
    * configure.ac (MTIME_RESOLUTION): notice if it erroneously
    expands to the empty string, i.e., fall back to 1 if
    $am_cv_filesystem_timestamp_resolution ended up being unset.
    * t/ax/test-defs.in (MTIME_RESOLUTION): also fall back to 1
    if the variable to not set, with a message.
    Fix other typos en passant.
    * HACKING: tweak.
---
 HACKING           | 10 +++++-----
 configure.ac      |  4 ++++
 m4/sanity.m4      | 57 +++++++++++++++++++++++++++++++++++++++++++++++--------
 t/ax/test-defs.in | 28 +++++++++++++++++++++------
 4 files changed, 80 insertions(+), 19 deletions(-)

diff --git a/HACKING b/HACKING
index ed644ea9f..c0b7702e9 100644
--- a/HACKING
+++ b/HACKING
@@ -204,10 +204,10 @@
 * To get a faithful and correct rebuild, run:
     ./bootstrap && ./config.status --recheck && make clean all
 
-* Usually, it is best to run again latest stable versions of Autoconf,
-  Libtool, etc., since that is what most users will do. Sometimes it may
-  be necessary to use the development versions due to bugs fixed,
-  etc. Whatever is first in PATH wins.
+* Usually, it is best to run against the latest stable versions of
+  Autoconf, Libtool, etc., since that is what most users will
+  do. However, sometimes it may be necessary to use the development
+  versions due to bugs fixed, etc. Whatever is first in PATH wins.
   (Some background: https://bugs.gnu.org/11347)
   
 * The Automake git tree currently carries three basic branches:
@@ -281,7 +281,7 @@
   to follow.  See the further points below for clarifications and minor
   corrections.
 
-      topic: brief description (this is the "summary line")
+      topic: brief description (this is the "summary line").
 
       <reference to relevant bugs, if any>
 
diff --git a/configure.ac b/configure.ac
index eb5383324..062db9935 100644
--- a/configure.ac
+++ b/configure.ac
@@ -191,6 +191,10 @@ AC_PROG_FGREP
 # supported by the filesystem hosting the build.  The value
 # will be acceptable to 'sleep' on this system.
 MTIME_RESOLUTION=$am_cv_filesystem_timestamp_resolution
+if test -z "$MTIME_RESOLUTION"; then
+  AC_MSG_NOTICE(am_cv_filesystem_timestamp_resolution strangely not set; using 
1)
+  MTIME_RESOLUTION=1
+fi
 AC_SUBST([MTIME_RESOLUTION])
 
 dnl FIXME: could we extract this in a simpler way through autoconf
diff --git a/m4/sanity.m4 b/m4/sanity.m4
index 59afa7b15..4504ef878 100644
--- a/m4/sanity.m4
+++ b/m4/sanity.m4
@@ -24,16 +24,20 @@ AS_IF([sleep 0.001 2>/dev/null], 
[am_cv_sleep_fractional_seconds=true],
 # nanosecond, matching clock_gettime.  However, it is probably not
 # possible to delay execution of a shell script for less than one
 # millisecond, due to process creation overhead and scheduling
-# granularity, so we don't check for anything finer than that.
+# granularity, so we don't check for anything finer than that. (See below.)
 AC_DEFUN([_AM_FILESYSTEM_TIMESTAMP_RESOLUTION], [dnl
 AC_REQUIRE([_AM_SLEEP_FRACTIONAL_SECONDS])
-AC_CACHE_CHECK([filesystem timestamp resolution], 
am_cv_filesystem_timestamp_resolution, [dnl
+AC_CACHE_CHECK([filesystem timestamp resolution],
+               am_cv_filesystem_timestamp_resolution, [dnl
 # Default to the worst case.
 am_cv_filesystem_timestamp_resolution=2
 
 # Only try to go finer than 1s if sleep can do it.
 am_try_resolutions=1
 if $am_cv_sleep_fractional_seconds; then
+  # Even a millisecond often causes a bunch of false positives,
+  # so just try a hundredth of a second. The time saved between .001 and
+  # .01 is not terribly consequential.
   am_try_resolutions="0.01 0.1 $am_try_resolutions"
 fi
 
@@ -48,12 +52,13 @@ rm -f conftest.ts?
 : > conftest.ts3
 
 # Make sure ls -t actually works.  Do 'set' in a subshell so we don't
-# clobber the current shell's arguments.
+# clobber the current shell's arguments. (Outer-level square brackets
+# are for m4; be careful, it's easy to get confused.)
 if (
      set X `[ls -t conftest.ts[12]]` &&
      {
-       test "$[*]" != "X conftest.ts1 conftest.ts2" ||
-       test "$[*]" != "X conftest.ts2 conftest.ts1";
+       test "$[]*" != "X conftest.ts1 conftest.ts2" ||
+       test "$[]*" != "X conftest.ts2 conftest.ts1";
      }
 ); then :; else
   # If neither matched, then we have a broken ls.  This can happen
@@ -64,7 +69,7 @@ if (
     ["Bad output from ls -t: \"`[ls -t conftest.ts[12]]`\""],
     [AS_MESSAGE_LOG_FD])
   AC_MSG_FAILURE([ls -t produces unexpected output.
-Make sure there is not a broken alias in your environment.])
+Make sure there is not a broken ls alias in your environment.])
 fi
 
 for am_try_res in $am_try_resolutions; do
@@ -84,11 +89,47 @@ for am_try_res in $am_try_resolutions; do
       test "$[]2" = conftest.ts3 &&
       test "$[]3" = conftest.ts2 &&
       test "$[]4" = conftest.ts1); then
-    am_cv_filesystem_timestamp_resolution=$am_try_res
-    break
+    #
+    # Ok, ls -t worked. We have one more thing to check: make.
+    # It can happen that everything else supports the subsecond mtimes,
+    # but make doesn't, notably on macOS, which ships make 3.81 from
+    # 2006 (the last one released under GPLv2). https://bugs.gnu.org/68808
+    # 
+    # So, first let's create a Makefile:
+    rm -f conftest.mk
+    echo 'conftest.ts1: conftest.ts2' >conftest.mk
+    echo '     touch conftest.ts2' >>conftest.mk
+    #
+    # Now, running
+    #   touch conftest.ts1; touch conftest.ts2; make
+    # should touch ts1 because ts2 is newer. This could happen by luck,
+    # but most often, it will fail if make's support is insufficient. So
+    # test for several consecutive successes.
+    # 
+    # (We reuse conftest.ts[12] because we still want to modify existing
+    # files, not create new ones, per above.)
+    n=0
+    make_ok=true
+    until test $n -eq 4; do
+      echo one > conftest.ts1
+      sleep $am_try_res
+      echo two > conftest.ts2 # ts2 should now be newer than ts1
+      if make -f conftest.mk | grep 'up to date' >/dev/null; then
+        make_ok=false
+        break # out of $n loop
+      fi
+      n=`expr $n + 1`
+    done
+    if $make_ok; then
+      # Everything we know to check worked out, so call this resolution good.
+      am_cv_filesystem_timestamp_resolution=$am_try_res
+      break # out of resolution loop
+    fi
+    # Otherwise, we'll go on to check the next resolution.
   fi
 done
 rm -f conftest.ts?
+# (end _am_filesystem_timestamp_resolution)
 ])])
 
 # AM_SANITY_CHECK
diff --git a/t/ax/test-defs.in b/t/ax/test-defs.in
index c1ead418e..275cfb2dc 100644
--- a/t/ax/test-defs.in
+++ b/t/ax/test-defs.in
@@ -64,7 +64,7 @@ case ${am_running_installcheck:=no} in
     am_system_acdir=""
     ;;
   *)
-    echo "$me: variable 'am_running_installcheck' has invalid"
+    echo "$me: variable 'am_running_installcheck' has invalid" \
          "value '$am_running_installcheck'" >&2
     exit 99
     ;;
@@ -172,7 +172,7 @@ 
GNU_CFLAGS=${AM_TESTSUITE_GNU_CFLAGS-${GNU_CFLAGS-'@GNU_CFLAGS@'}}
 GNU_GCJ=${AM_TESTSUITE_GNU_GCJ-${GNU_GCJ-'@GNU_GCJ@'}}
 GNU_GCJFLAGS=${AM_TESTSUITE_GNU_GCJFLAGS-${GNU_GCJFLAGS-'@GNU_GCJFLAGS@'}}
 
-# No all versions of Tex support '--version', so we use a configure
+# Not all versions of Tex support '--version', so we use a configure
 # check to decide if tex is available.  This decision is embodied in
 # this variable.
 TEX=${AM_TESTSUITE_TEX-'@TEX@'}
@@ -190,8 +190,24 @@ case $MTIME_RESOLUTION in
          grep 'Features:.*subsecond-mtime' > /dev/null 2>&1 &&
        $AUTOM4TE --version 2>&1 |
          grep 'Features:.*subsecond-mtime' > /dev/null 2>&1; then
-      :
+      # subsecond-mtime should be supported; use the timestamp
+      # resolution that we determined. If it hasn't been determined,
+      # that's a bug somewhere.
+      if test -n "$am_cv_filesystem_timestamp_resolution"; then
+        #echo "$me: got $am_cv_filesystem_timestamp_resolution" >&2
+        MTIME_RESOLUTION=$am_cv_filesystem_timestamp_resolution
+      else
+        # ends up in test-suite.log.
+        echo "$me: subsecond-mtime supported per automake and auto4mte" \
+             "--version, but am_cv_filesystem_timestamp_resolution not set;" \
+             "that's an error somewhere. Proceeding with value 1." >&2
+        MTIME_RESOLUTION=1
+      fi
     else
+      #echo "$me: --version doesn't support subsecond-mtime" >&2
+      #$AUTOMAKE --version >&2
+      #$AUTOM4TE --version >&2
+      #
       MTIME_RESOLUTION=1
       # we must not sleep for fractional seconds when autom4te does not
       # support subsecond-mtimes, even when sleep supports it. See bug#67670.
@@ -202,10 +218,10 @@ case $MTIME_RESOLUTION in
 esac
 
 # This sleep variable is used explicitly in some tests to avoid
-# too-quick creation. I (Karl) believe that was an incomplete workaround
+# too-quick creation. Seems likely this was an incomplete workaround
 # for this whole subsecond-mtime problem. With this set to "sleep 1",
-# there were still random parallelization failures, without also setting
-# am_cv_sleep_fractional_seconds=false as above.
+# there were still random parallelization failures; setting
+# am_cv_sleep_fractional_seconds=false as above was still needed.
 # 
 sleep="sleep $MTIME_RESOLUTION"