Allow extensions to install built as well as unbuilt headers.

Commit df163230b overlooked the case that an out-of-tree extension
might need to build its header files (e.g. via ./configure). If it is
also doing a VPATH build, the HEADERS_* rules in the original commit
would then fail to find the files, since they would be looking only
under $(srcdir) and not in the build directory.

Fix by adding HEADERS_built and HEADERS_built_$(MODULE) which behave
like DATA_built in that they look in the build dir rather than the
source dir (and also make the files dependencies of the "all" target).

No Windows support appears to be needed for this, since it is only
relevant to out-of-tree builds (no support exists in Mkvcbuild.pm to
build extension header files in any case).

doc/src/sgml/extend.sgml

@@ -1224,9 +1224,10 @@ include $(PGXS)
 
      <varlistentry>
       <term><varname>HEADERS</varname></term>
+      <term><varname>HEADERS_built</varname></term>
       <listitem>
        <para>
-        files to install under
+        files to (optionally build and) install under
         <literal><replaceable>prefix</replaceable>/include/server/$MODULEDIR/$MODULE_big</literal>
        </para>
       </listitem>
@@ -1234,12 +1235,21 @@ include $(PGXS)
 
      <varlistentry>
       <term><varname>HEADERS_$MODULE</varname></term>
+      <term><varname>HEADERS_built_$MODULE</varname></term>
       <listitem>
        <para>
-        files to install under
+        Files to install (after building if specified) under
         <literal><replaceable>prefix</replaceable>/include/server/$MODULEDIR/$MODULE</literal>,
         where <literal>$MODULE</literal> must be a module name used
-        in <literal>MODULES</literal> or <literal>MODULE_big</literal>
+        in <literal>MODULES</literal> or <literal>MODULE_big</literal>.
+       </para>
+       <para>
+        It is legal to use both variables for the same module, or any
+        combination, unless you have two module names in the
+        <literal>MODULES</literal> list that differ only by the presence of a
+        prefix <literal>built_</literal>, which would cause ambiguity. In
+        that (hopefully unlikely) case, you should use only the
+        <literal>HEADERS_built_$MODULE</literal> variables.
        </para>
       </listitem>
      </varlistentry>

src/makefiles/pgxs.mk

@@ -39,9 +39,11 @@
 #   SCRIPTS_built -- script files (not binaries) to install into $PREFIX/bin,
 #     which need to be built first
 #   HEADERS -- files to install into $(includedir_server)/$MODULEDIR/$MODULE_big
+#   HEADERS_built -- as above but built first
 #   HEADERS_$(MODULE) -- files to install into
 #     $(includedir_server)/$MODULEDIR/$MODULE; the value of $MODULE must be
 #     listed in MODULES or MODULE_big
+#   HEADERS_built_$(MODULE) -- as above but built first
 #   REGRESS -- list of regression test cases (without suffix)
 #   REGRESS_OPTS -- additional switches to pass to pg_regress
 #   NO_INSTALLCHECK -- don't define an installcheck target, useful e.g. if
@@ -115,26 +117,54 @@ ifdef PG_CPPFLAGS
 override CPPFLAGS := $(PG_CPPFLAGS) $(CPPFLAGS)
 endif
 
+# get list of all names used with or without built_ prefix
+# note that use of HEADERS_built_foo will get both "foo" and "built_foo",
+# we cope with that later when filtering this list against MODULES.
+# If someone wants to name a module "built_foo", they can do that and it
+# works, but if they have MODULES = foo built_foo  then they will need to
+# force building of all headers and use HEADERS_built_foo and
+# HEADERS_built_built_foo.
 HEADER_alldirs := $(patsubst HEADERS_%,%,$(filter HEADERS_%, $(.VARIABLES)))
+HEADER_alldirs += $(patsubst HEADERS_built_%,%,$(filter HEADERS_built_%, $(.VARIABLES)))
+
+# collect all names of built headers to use as a dependency
+HEADER_allbuilt =
 
 # HEADERS is an error in the absence of MODULE_big to provide a dir name
 ifdef MODULE_big
 ifdef HEADERS
 HEADER_dirs := $(MODULE_big)
-HEADERS_$(MODULE_big) = $(HEADERS)
+HEADER_unbuilt_$(MODULE_big) = $(HEADERS)
+HEADER_built_$(MODULE_big) = $(HEADERS_built)
+HEADER_allbuilt += $(HEADERS_built)
+else ifdef HEADERS_built
+HEADER_dirs := $(MODULE_big)
+HEADER_built_$(MODULE_big) = $(HEADERS_built)
+HEADER_allbuilt += $(HEADERS_built)
 else
-HEADER_dirs := $(filter $(MODULE_big),$(HEADER_alldirs))
+# file might have used HEADERS_foo or HEADERS_built_foo, so check for those
+HEADER_dirs := $(if $(filter $(MODULE_big) built_$(MODULE_big),$(HEADER_alldirs)),$(MODULE_big))
+HEADER_unbuilt_$(MODULE_big) = $(HEADERS_$(MODULE_big))
+HEADER_built_$(MODULE_big) = $(HEADERS_built_$(MODULE_big))
+HEADER_allbuilt += $(HEADERS_built_$(MODULE_big))
 endif
 else
 ifdef HEADERS
 $(error HEADERS requires MODULE_big to be set)
 endif
-HEADER_dirs := $(filter $(MODULES),$(HEADER_alldirs))
+# make list of modules that have either HEADERS_foo or HEADERS_built_foo
+HEADER_dirs := $(foreach m,$(MODULES),$(if $(filter $(m) built_$(m),$(HEADER_alldirs)),$(m)))
+# assign HEADER_unbuilt_foo and HEADER_built_foo, but make sure
+# that "built" takes precedence in the case of conflict, by removing
+# conflicting module names when matching the unbuilt name
+$(foreach m,$(filter-out $(addprefix built_,$(MODULES)),$(MODULES)),$(eval HEADER_unbuilt_$(m) = $$(HEADERS_$(m))))
+$(foreach m,$(MODULES),$(eval HEADER_built_$(m) = $$(HEADERS_built_$(m))))
+$(foreach m,$(MODULES),$(eval HEADER_allbuilt += $$(HEADERS_built_$(m))))
 endif
 
 # HEADERS_foo requires that "foo" is in MODULES as a sanity check
-ifneq ($(filter-out $(HEADER_dirs),$(HEADER_alldirs)),)
-$(error $(patsubst %,HEADERS_%,$(filter-out $(HEADER_dirs),$(HEADER_alldirs))) defined with no module)
+ifneq ($(filter-out $(HEADER_dirs) $(addprefix built_,$(HEADER_dirs)),$(HEADER_alldirs)),)
+$(error $(patsubst %,HEADERS_%,$(filter-out $(HEADER_dirs) $(addprefix built_,$(HEADER_dirs)),$(HEADER_alldirs))) defined with no module)
 endif
 
 # Functions for generating install/uninstall commands; the blank lines
@@ -142,7 +172,7 @@ endif
 # $(call install_headers,dir,headers)
 define install_headers
 $(MKDIR_P) '$(DESTDIR)$(includedir_server)/$(incmoduledir)/$(1)/'
-$(INSTALL_DATA) $(addprefix $(srcdir)/, $(2)) '$(DESTDIR)$(includedir_server)/$(incmoduledir)/$(1)/'
+$(INSTALL_DATA) $(2) '$(DESTDIR)$(includedir_server)/$(incmoduledir)/$(1)/'
 
 endef
 # $(call uninstall_headers,dir,headers)
@@ -152,7 +182,7 @@ rm -f $(addprefix '$(DESTDIR)$(includedir_server)/$(incmoduledir)/$(1)'/, $(notd
 endef
 
 
-all: $(PROGRAM) $(DATA_built) $(SCRIPTS_built) $(addsuffix $(DLSUFFIX), $(MODULES)) $(addsuffix .control, $(EXTENSION))
+all: $(PROGRAM) $(DATA_built) $(HEADER_allbuilt) $(SCRIPTS_built) $(addsuffix $(DLSUFFIX), $(MODULES)) $(addsuffix .control, $(EXTENSION))
 
 ifeq ($(with_llvm), yes)
 all: $(addsuffix .bc, $(MODULES)) $(patsubst %.o,%.bc, $(OBJS))
@@ -199,7 +229,8 @@ ifdef SCRIPTS_built
 	$(INSTALL_SCRIPT) $(SCRIPTS_built) '$(DESTDIR)$(bindir)/'
 endif # SCRIPTS_built
 ifneq ($(strip $(HEADER_dirs)),)
-	$(foreach dir,$(HEADER_dirs),$(if $(HEADERS_$(dir)),$(call install_headers,$(dir),$(HEADERS_$(dir)))))
+	$(foreach dir,$(HEADER_dirs),$(if $(HEADER_unbuilt_$(dir)),$(call install_headers,$(dir),$(addprefix $(srcdir)/, $(HEADER_unbuilt_$(dir))))))
+	$(foreach dir,$(HEADER_dirs),$(if $(HEADER_built_$(dir)),$(call install_headers,$(dir),$(HEADER_built_$(dir)))))
 endif # HEADERS
 ifdef MODULE_big
 ifeq ($(with_llvm), yes)
@@ -266,7 +297,7 @@ ifdef SCRIPTS_built
 	rm -f $(addprefix '$(DESTDIR)$(bindir)'/, $(SCRIPTS_built))
 endif
 ifneq ($(strip $(HEADER_dirs)),)
-	$(foreach dir,$(HEADER_dirs),$(if $(HEADERS_$(dir)),$(call uninstall_headers,$(dir),$(HEADERS_$(dir)))))
+	$(foreach dir,$(HEADER_dirs),$(call uninstall_headers,$(dir),$(HEADER_unbuilt_$(dir)) $(HEADER_built_$(dir))))
 endif # HEADERS
 
 ifdef MODULE_big