[automake-commit] branch master updated: automake: disable GNU make's internal pattern rules, for speed.

[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=dbdfa65c2d75383f3defc734dd9aab86da6ae29d

The following commit(s) were added to refs/heads/master by this push:
     new dbdfa65c2 automake: disable GNU make's internal pattern rules, for 
speed.
dbdfa65c2 is described below

commit dbdfa65c2d75383f3defc734dd9aab86da6ae29d
Author: Bruno Haible <bruno@clisp.org>
AuthorDate: Thu Jul 20 18:03:27 2023 -0700

    automake: disable GNU make's internal pattern rules, for speed.
    
    From https://bugs.gnu.org/64743.
    
    * lib/am/footer.am: Disable GNU make's internal pattern rules.
    * lib/Automake/Rule.pm (_conditionals_for_rule): Add special handling
    for these pattern rules from footer.am.
    (define): Likewise.
    * t/nodep.sh: Update test to avoid matching the new %:: rules.
    * t/fnoc.sh: Update test to avoid matching the new %:: SCCS rule.
    
    * NEWS: Mention this.
    * doc/automake.texi (Suffixes): Likewise.
    (Doc changes written by Karl.)
---
 NEWS                 |  3 +++
 doc/automake.texi    |  8 ++++++++
 lib/Automake/Rule.pm | 39 +++++++++++++++++++++++----------------
 lib/am/footer.am     | 11 +++++++++++
 t/fnoc.sh            |  7 ++++++-
 t/nodep.sh           |  2 +-
 6 files changed, 52 insertions(+), 18 deletions(-)

diff --git a/NEWS b/NEWS
index c64d4ef15..ced0fd640 100644
--- a/NEWS
+++ b/NEWS
@@ -21,6 +21,9 @@ New in 1.17:
   - Variables using escaped \# will trigger portability warnings, but be
     retained when appended.  GNU Make & BSD Makes are known to support it.
 
+  - GNU Make's default pattern rules are disabled, for speed and debugging.
+    (.SUFFIXES was already cleared.) (bug#64743)
+
   - For Texinfo documents, if a .texi.in file exists, but no .texi, the
     .texi.in will be read. Texinfo source files need not be present at
     all, and if present, need not contain @setfilename. Then the file name
diff --git a/doc/automake.texi b/doc/automake.texi
index 4561d1948..3b4f06e73 100644
--- a/doc/automake.texi
+++ b/doc/automake.texi
@@ -10977,6 +10977,14 @@ Automake generate the suffix list for 
@code{.SUFFIXES}.  Any given
 @code{SUFFIXES} go at the start of the generated suffixes list, followed
 by Automake generated suffixes not already in the list.
 
+@c https://bugs.gnu.org/64743.
+@cindex built-in suffix and pattern rules, disabled
+@cindex suffix rules of Make, disabled
+@cindex pattern rules of GNU Make, disabled
+Automake disables the Make program's built-in rules with a
+@code{.SUFFIXES:} rule, and then adds whatever suffixes are
+necessary.  Automake also disables GNU Make's built-in pattern rules.
+
 @node Include
 @chapter Include
 
diff --git a/lib/Automake/Rule.pm b/lib/Automake/Rule.pm
index 9f72d2728..52ee3be4a 100644
--- a/lib/Automake/Rule.pm
+++ b/lib/Automake/Rule.pm
@@ -695,6 +695,9 @@ sub _conditionals_for_rule ($$$$)
 
   return $cond if !$message; # No ambiguity.
 
+  # Don't coalesce the several pattern rules from footer.am into a single one.
+  return $cond if $target eq "%:" && $where->get =~ /\/am\/footer\.am$/;
+
   if ($owner == RULE_USER)
     {
       # For user rules, just diagnose the ambiguity.
@@ -764,23 +767,27 @@ sub define ($$$$$)
 
   my $tdef = _rule_defn_with_exeext_awareness ($target, $cond, $where);
 
-  # A GNU make-style pattern rule has a single "%" in the target name.
-  msg ('portability', $where,
-       "'%'-style pattern rules are a GNU make extension")
-    if $target =~ /^[^%]*%[^%]*$/;
-
-  # See whether this is a duplicated target declaration.
-  if ($tdef)
+  # The pattern rules in footer.am look like duplicates, but really aren't.
+  if ($source !~ /\/am\/footer\.am$/)
     {
-      # Diagnose invalid target redefinitions, if any.  Note that some
-      # target redefinitions are valid (e.g., for multiple-targets
-      # pattern rules).
-      _maybe_warn_about_duplicated_target ($target, $tdef, $source,
-                                           $owner, $cond, $where);
-      # Return so we don't redefine the rule in our tables, don't check
-      # for ambiguous condition, etc.  The rule will be output anyway
-      # because '&read_am_file' ignores the return code.
-      return ();
+      # A GNU make-style pattern rule has a single "%" in the target name.
+      msg ('portability', $where,
+           "'%'-style pattern rules are a GNU make extension")
+        if $target =~ /^[^%]*%[^%]*$/;
+
+      # See whether this is a duplicated target declaration.
+      if ($tdef)
+        {
+          # Diagnose invalid target redefinitions, if any.  Note that some
+          # target redefinitions are valid (e.g., for multiple-targets
+          # pattern rules).
+          _maybe_warn_about_duplicated_target ($target, $tdef, $source,
+                                               $owner, $cond, $where);
+          # Return so we don't redefine the rule in our tables, don't check
+          # for ambiguous condition, etc.  The rule will be output anyway
+          # because '&read_am_file' ignores the return code.
+          return ();
+        }
     }
 
   my $rule = _crule $target;
diff --git a/lib/am/footer.am b/lib/am/footer.am
index 9715c826c..388defb14 100644
--- a/lib/am/footer.am
+++ b/lib/am/footer.am
@@ -17,3 +17,14 @@
 # Tell versions [3.59,3.63) of GNU make to not export all variables.
 # Otherwise a system limit (for SysV at least) may be exceeded.
 .NOEXPORT:
+
+# Tell GNU make to disable its built-in pattern rules.
+## This reduces make's internal processing.
+## Recommended by Paul Smith in
+## <https://lists.gnu.org/archive/html/bug-make/2023-07/msg00063.html>.
+## These rules have no effect on non-GNU make implementations.
+%:: %,v
+%:: RCS/%,v
+%:: RCS/%
+%:: s.%
+%:: SCCS/s.%
diff --git a/t/fnoc.sh b/t/fnoc.sh
index 97b694c63..7d6b49096 100644
--- a/t/fnoc.sh
+++ b/t/fnoc.sh
@@ -35,5 +35,10 @@ END
 $ACLOCAL
 $AUTOMAKE
 
-grep '[^F]CC' Makefile.in | grep -v MKDEP && exit 1
+# In bug#64743, explicit rules were added to disable make's default
+# built-in rules, including one for SCCS:
+# %:: SCCS/s.%
+# So don't match that. Meanwhile, MKDEP does not occur in the output
+# any more, but leaving it in in case it comes back.
+grep '[^F]CC' Makefile.in | grep -v MKDEP | grep -v SCCS && exit 1
 exit 0
diff --git a/t/nodep.sh b/t/nodep.sh
index 4201c8ead..0174b838e 100644
--- a/t/nodep.sh
+++ b/t/nodep.sh
@@ -37,6 +37,6 @@ $ACLOCAL
 $AUTOMAKE
 
 sed 's/printf .*%s//' Makefile.in > Makefile.tmp
-grep '%' Makefile.tmp && exit 1
+grep -v '^%::' Makefile.tmp | grep '%' && exit 1
 
 :