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[PATCH 1/2] Makefile: use "find" to determine static header dependencies

From
Jeff King <peff@peff.net>
Date
Aug 21, 2014, 08:29 UTC
Message-ID
<20140821082935.GA25763@peff.net>
In-Reply-To
<20140821082440.GA16402@peff.net>

Most modern platforms will use automatically computed header dependencies to figure out when a C file needs to be rebuilt due to a header changing. With old compilers, however, we fall back to a static list of header files. If any of them changes, we recompile everything. This is overly conservative, but the best we can do without compiler support.

It is unfortunately easy for our static header list to grow stale, as none of the regular developers make use of it. Instead of trying to keep it up to date, let's invoke "find" to generate the list dynamically.

We'd like to avoid running find at all when it is not necessary, since it may add a non-trivial amount of time to the build. Make is _almost_ smart enough to avoid evaluating the function when it is not necessary. For the static header dependencies, we include $(LIB_H) as a dependency only if COMPUTE_HEADER_DEPENDENCIES is turned off, so we don't trigger its use there unless necessary. So far so good.

However, we do always define $(LIB_H) as a dependency of po/git.pot. Even though we do not actually try to build that target, make will still evaluate the dependencies when reading the Makefile, and expand the variable. This is not ideal because almost nobody wants to build po/git.pot (only the translation maintainer does it, and even then only once or twice per release). We can hack around this by invoking a sub-make which evaluates the variable only when po/git.pot is actually being built.

Signed-off-by: Jeff King <peff@peff.net>
---
I also optimized the "find" a bit by pruning out some
directories that are almost certainly uninteresting. That
means we wouldn't catch an include of "t/foo.h", but I think
that is probably an OK assumption.

I'm open to attempts to improve my ugly git.pot hack. I thought at first it was caused by the use of ":=" in assigning LOCALIZED_C, but after much testing, I think it is actually the expansion of the dependencies.

 Makefile | 143 ++++++---------------------------------------------------------
 1 file changed, 13 insertions(+), 130 deletions(-)
diff --git a/Makefile b/Makefile
index 2320de5..08dd973 100644
--- a/Makefile
+++ b/Makefile
@@ -432,7 +432,6 @@ XDIFF_OBJS =
 VCSSVN_OBJS =
 GENERATED_H =
 EXTRA_CPPFLAGS =
-LIB_H =
 LIB_OBJS =
 PROGRAM_OBJS =
 PROGRAMS =
@@ -631,131 +630,11 @@ VCSSVN_LIB = vcs-svn/lib.a
 
 GENERATED_H += common-cmds.h
 
-LIB_H += advice.h
-LIB_H += archive.h
-LIB_H += argv-array.h
-LIB_H += attr.h
-LIB_H += bisect.h
-LIB_H += blob.h
-LIB_H += branch.h
-LIB_H += builtin.h
-LIB_H += bulk-checkin.h
-LIB_H += bundle.h
-LIB_H += cache-tree.h
-LIB_H += cache.h
-LIB_H += color.h
-LIB_H += column.h
-LIB_H += commit.h
-LIB_H += compat/bswap.h
-LIB_H += compat/mingw.h
-LIB_H += compat/obstack.h
-LIB_H += compat/poll/poll.h
-LIB_H += compat/precompose_utf8.h
-LIB_H += compat/terminal.h
-LIB_H += compat/win32/dirent.h
-LIB_H += compat/win32/pthread.h
-LIB_H += compat/win32/syslog.h
-LIB_H += connected.h
-LIB_H += convert.h
-LIB_H += credential.h
-LIB_H += csum-file.h
-LIB_H += decorate.h
-LIB_H += delta.h
-LIB_H += diff.h
-LIB_H += diffcore.h
-LIB_H += dir.h
-LIB_H += exec_cmd.h
-LIB_H += ewah/ewok.h
-LIB_H += ewah/ewok_rlw.h
-LIB_H += fetch-pack.h
-LIB_H += fmt-merge-msg.h
-LIB_H += fsck.h
-LIB_H += gettext.h
-LIB_H += git-compat-util.h
-LIB_H += gpg-interface.h
-LIB_H += graph.h
-LIB_H += grep.h
-LIB_H += hashmap.h
-LIB_H += help.h
-LIB_H += http.h
-LIB_H += kwset.h
-LIB_H += levenshtein.h
-LIB_H += line-log.h
-LIB_H += line-range.h
-LIB_H += list-objects.h
-LIB_H += ll-merge.h
-LIB_H += log-tree.h
-LIB_H += mailmap.h
-LIB_H += merge-blobs.h
-LIB_H += merge-recursive.h
-LIB_H += mergesort.h
-LIB_H += notes-cache.h
-LIB_H += notes-merge.h
-LIB_H += notes-utils.h
-LIB_H += notes.h
-LIB_H += object.h
-LIB_H += pack-objects.h
-LIB_H += pack-revindex.h
-LIB_H += pack.h
-LIB_H += pack-bitmap.h
-LIB_H += parse-options.h
-LIB_H += patch-ids.h
-LIB_H += pathspec.h
-LIB_H += pkt-line.h
-LIB_H += prio-queue.h
-LIB_H += progress.h
-LIB_H += prompt.h
-LIB_H += quote.h
-LIB_H += reachable.h
-LIB_H += reflog-walk.h
-LIB_H += refs.h
-LIB_H += remote.h
-LIB_H += rerere.h
-LIB_H += resolve-undo.h
-LIB_H += revision.h
-LIB_H += run-command.h
-LIB_H += send-pack.h
-LIB_H += sequencer.h
-LIB_H += sha1-array.h
-LIB_H += sha1-lookup.h
-LIB_H += shortlog.h
-LIB_H += sideband.h
-LIB_H += sigchain.h
-LIB_H += strbuf.h
-LIB_H += streaming.h
-LIB_H += string-list.h
-LIB_H += submodule.h
-LIB_H += tag.h
-LIB_H += tar.h
-LIB_H += thread-utils.h
-LIB_H += transport.h
-LIB_H += tree-walk.h
-LIB_H += tree.h
-LIB_H += unpack-trees.h
-LIB_H += unicode_width.h
-LIB_H += url.h
-LIB_H += urlmatch.h
-LIB_H += userdiff.h
-LIB_H += utf8.h
-LIB_H += varint.h
-LIB_H += vcs-svn/fast_export.h
-LIB_H += vcs-svn/line_buffer.h
-LIB_H += vcs-svn/repo_tree.h
-LIB_H += vcs-svn/sliding_window.h
-LIB_H += vcs-svn/svndiff.h
-LIB_H += vcs-svn/svndump.h
-LIB_H += walker.h
-LIB_H += wildmatch.h
-LIB_H += wt-status.h
-LIB_H += xdiff-interface.h
-LIB_H += xdiff/xdiff.h
-LIB_H += xdiff/xdiffi.h
-LIB_H += xdiff/xemit.h
-LIB_H += xdiff/xinclude.h
-LIB_H += xdiff/xmacros.h
-LIB_H += xdiff/xprepare.h
-LIB_H += xdiff/xtypes.h
-LIB_H += xdiff/xutils.h
+LIB_H = $(shell find . \
+	-name .git -prune -o \
+	-name t -prune -o \
+	-name Documentation -prune -o \
+	-name '*.h' -print)
 
 LIB_OBJS += abspath.o
 LIB_OBJS += advice.o
@@ -1381,7 +1260,6 @@ ifdef NO_INET_PTON
 endif
 ifndef NO_UNIX_SOCKETS
 	LIB_OBJS += unix-socket.o
-	LIB_H += unix-socket.h
 	PROGRAM_OBJS += credential-cache.o
 	PROGRAM_OBJS += credential-cache--daemon.o
 endif
@@ -1405,12 +1283,10 @@ endif
 ifdef BLK_SHA1
 	SHA1_HEADER = "block-sha1/sha1.h"
 	LIB_OBJS += block-sha1/sha1.o
-	LIB_H += block-sha1/sha1.h
 else
 ifdef PPC_SHA1
 	SHA1_HEADER = "ppc/sha1.h"
 	LIB_OBJS += ppc/sha1.o ppc/sha1ppc.o
-	LIB_H += ppc/sha1.h
 else
 ifdef APPLE_COMMON_CRYPTO
 	COMPAT_CFLAGS += -DCOMMON_DIGEST_FOR_OPENSSL
@@ -2128,7 +2004,7 @@ XGETTEXT_FLAGS_C = $(XGETTEXT_FLAGS) --language=C \
 XGETTEXT_FLAGS_SH = $(XGETTEXT_FLAGS) --language=Shell \
 	--keyword=gettextln --keyword=eval_gettextln
 XGETTEXT_FLAGS_PERL = $(XGETTEXT_FLAGS) --keyword=__ --language=Perl
-LOCALIZED_C := $(C_OBJ:o=c) $(LIB_H) $(GENERATED_H)
+LOCALIZED_C := $(C_OBJ:o=c) $(GENERATED_H)
 LOCALIZED_SH := $(SCRIPT_SH)
 LOCALIZED_PERL := $(SCRIPT_PERL)
 
@@ -2138,6 +2014,8 @@ LOCALIZED_SH += t/t0200/test.sh
 LOCALIZED_PERL += t/t0200/test.perl
 endif
 
+ifdef REAL_GIT_POT
+LOCALIZED_C += $(LIB_H)
 po/git.pot: $(LOCALIZED_C)
 	$(QUIET_XGETTEXT)$(XGETTEXT) -o$@+ $(XGETTEXT_FLAGS_C) $(LOCALIZED_C)
 	$(QUIET_XGETTEXT)$(XGETTEXT) -o$@+ --join-existing $(XGETTEXT_FLAGS_SH) \
@@ -2145,6 +2023,11 @@ po/git.pot: $(LOCALIZED_C)
 	$(QUIET_XGETTEXT)$(XGETTEXT) -o$@+ --join-existing $(XGETTEXT_FLAGS_PERL) \
 		$(LOCALIZED_PERL)
 	mv $@+ $@
+else
+.PHONY: po/git.pot
+po/git.pot:
+	@$(MAKE) po/git.pot REAL_GIT_POT=Yes
+endif
 
 pot: po/git.pot
 

-- 
2.1.0.346.ga0367b9
Previous: Jeff KingNext: Jonathan Nieder
Message 4 of 27 in “Update hard-coded header dependencies”
  1. Update hard-coded header dependenciesJonathan Nieder, Aug 8, 2014
  2. Jeff KingAug 10, 2014
  3. Jeff KingAug 21, 2014
  4. 1/2 Makefile: use "find" to determine static header dependenciesJeff King, Aug 21, 2014
  5. Jonathan NiederAug 21, 2014
  6. Jeff KingAug 22, 2014
  7. 0/3 dropping manually-maintained LIB_HJeff King, Aug 22, 2014
  8. 1/3 i18n: treat "make pot" as an explicitly-invoked targetJeff King, Aug 22, 2014
  9. 2/3 Makefile: use `find` to determine static header dependenciesJeff King, Aug 22, 2014
  10. Junio C HamanoAug 25, 2014
  11. Jeff KingAug 25, 2014
  12. Jonathan NiederAug 25, 2014
  13. Jeff KingAug 25, 2014
  14. Jeff KingAug 25, 2014
  15. Jonathan NiederAug 25, 2014
  16. Junio C HamanoAug 25, 2014
  17. Jonathan NiederAug 25, 2014
  18. Junio C HamanoAug 25, 2014
  19. Jeff KingAug 26, 2014
  20. Junio C HamanoAug 26, 2014
  21. Jeff KingAug 26, 2014
  22. Junio C HamanoAug 26, 2014
  23. 3/3 Makefile: drop CHECK_HEADER_DEPENDENCIES codeJeff King, Aug 22, 2014
  24. Jiang XinAug 23, 2014
  25. 2/2 Makefile: drop CHECK_HEADER_DEPENDENCIES codeJeff King, Aug 21, 2014
  26. Junio C HamanoAug 10, 2014
  27. Junio C HamanoAug 10, 2014

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