From 755bcf086dc163d72d1d2fa1f1d708f6ac75910a Mon Sep 17 00:00:00 2001
From: Reid Spencer <rspencer@reidspencer.com>
Date: Wed, 24 Aug 2005 10:43:10 +0000
Subject: [PATCH] For PR619: Make any header files that are automatically
 generated be preconditions of the compilation. This ensures that if a *.h.in
 file is changed then its corresponding *.h file gets updated on the next
 rebuild. Note that this can lead to confusing (but correct) results if the
 *.h.in file changed unsubstantially so that autoheader doesn't update the *.h
 file. In that case, manually touch the *.h file in question to restore order.
 Moral of the story, if you're going to "touch" a *.in file then modify it
 substantially.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@23006 91177308-0d34-0410-b5e6-96231b3b80d8
---
 Makefile.rules        | 16 ++++++++++++++++
 autoconf/configure.ac |  4 ++++
 2 files changed, 20 insertions(+)

diff --git a/Makefile.rules b/Makefile.rules
index 7dfb2b41507..09c0a9c1722 100644
--- a/Makefile.rules
+++ b/Makefile.rules
@@ -28,6 +28,13 @@ TopLevelTargets  := check dist dist-check dist-clean tags dist-gzip dist-bzip2 \
 UserTargets      := $(RecursiveTargets) $(LocalTargets) $(TopLevelTargets)
 InternalTargets  := preconditions distdir dist-hook
 
+FilesToConfig := \
+  include/llvm/Config/config.h \
+  include/llvm/Support/DataTypes.h \
+  include/llvm/ADT/hash_map \
+  include/llvm/ADT/hash_set \
+  include/llvm/ADT/iterator
+
 ################################################################################
 # INITIALIZATION: Basic things the makefile needs
 ################################################################################
@@ -77,6 +84,9 @@ ifneq ($(MakefileConfigIn),)
 PreConditions      += $(MakefileConfig)
 endif
 
+FilesToConfigPATH  := $(addprefix $(PROJ_OBJ_ROOT)/,$(FilesToConfig))
+PreConditions      += $(FilesToConfigPATH)
+
 preconditions : $(PreConditions)
 
 #------------------------------------------------------------------------
@@ -134,6 +144,11 @@ $(ConfigStatusScript): $(ConfigureScript)
 	  $(ConfigStatusScript) --recheck $(ConfigureScriptFLAGS) && \
 	  $(ConfigStatusScript)
 
+.PRECIOUS: $(FilesToConfigPATH)
+$(FilesToConfigPATH) : $(PROJ_OBJ_ROOT)/% : $(PROJ_SRC_ROOT)/%.in 
+	$(Echo) Regenerating $*
+	$(Verb) cd $(PROJ_OBJ_ROOT) && $(ConfigStatusScript) $*
+
 #------------------------------------------------------------------------
 # Make sure the configuration makefile is up to date
 #------------------------------------------------------------------------
@@ -1576,3 +1591,4 @@ printvars::
 	$(Echo) "YaccFiles    : " '$(YaccFiles)'
 	$(Echo) "LexFiles     : " '$(LexFiles)'
 	$(Echo) "Module       : " '$(Module)'
+	$(Echo) "FilesToConfig: " '$(FilesToConfigPATH)'
diff --git a/autoconf/configure.ac b/autoconf/configure.ac
index 0c184516e3d..661fc1d3501 100644
--- a/autoconf/configure.ac
+++ b/autoconf/configure.ac
@@ -634,6 +634,10 @@ dnl===
 dnl===-----------------------------------------------------------------------===
 
 dnl Configure header files
+dnl WARNING: dnl If you add or remove any of the following config headers, then
+dnl you MUST also update Makefile.rules so that the variable FilesToConfig
+dnl contains the same list of files as AC_CONFIG_HEADERS below. This ensures the
+dnl files can be updated automatically when their *.in sources change.
 AC_CONFIG_HEADERS([include/llvm/Config/config.h])
 AC_CONFIG_HEADERS([include/llvm/Support/DataTypes.h])
 AC_CONFIG_HEADERS([include/llvm/ADT/hash_map])
-- 
2.34.1