Auto-generate libc-modules.h

Remove libc-modules.h from the tree and auto-generate it from
soversions.i and the list of modules in the built-modules variable
defined in Makeconfig.  Macros generated have increasing numbered
values, with built-modules having lower values starting from 1,
following which a separator value LIBS_BEGIN is added and then finally
the library names from soversions.i are appended to the list.  This
allows us to conveniently differentiate between the versioned
libraries and other built modules, which is needed in errno.h and
netdb.h to decide whether to use an internal symbol or an external
one.

Verified that generated code remains unchanged on x86_64.

	* Makeconfig (built-modules): List non-library modules to be
	built.
	(module-cppflags): Include libc-modules.h for
	everything except shlib-versions.v.i.
	(CPPFLAGS): Use it.
	(before-compile): Add libc-modules.h.
	($(common-objpfx)libc-modules.h,
	$(common-objpfx)libc-modules.stmp): New targets.
	(common-generated): Add libc-modules.h and libc-modules.stmp.
	($(common-objpfx)Versions.v.i): Depend on libc-modules.h.
	* include/libc-symbols.h: Don't include libc-modules.h.
	* include/libc-modules.h: Remove file.
	* scripts/gen-libc-modules.awk: New script to generate
	libc-modules.h.
	* sysdeps/unix/Makefile ($(common-objpfx)sysd-syscalls):
	Depend on libc-modules.stmp.

1 files changed, 38 insertions, 2 deletions

diff --git a/Makeconfig b/Makeconfig
index 9f88f7ca5b..1a26cc5568 100644
--- a/Makeconfig
+++ b/Makeconfig
@@ -813,20 +813,39 @@ endif	# $(+cflags) == ""
 # of many little headers in the include directory.
 libio-include = -I$(..)libio
 
+# List of non-library modules that we build.
+built-modules = iconvprogs iconvdata ldconfig lddlibc4 libmemusage \
+		libSegFault libpcprofile librpcsvc locale-programs \
+		memusagestat nonlib nscd extramodules libnldbl
+
+# We don't include libc-modules.h when these targets are being built.  These
+# targets don't (and will likely never need to) use the IS_IN facility.  In
+# fact, shlib-versions should not use it because that will create a circular
+# dependency as libc-modules.h is generated from shlib-versions.
+skip-module-cppflags = shlib-versions.v.i Versions.v.i
+
 in-module = $(subst -,_,$(firstword $(libof-$(basename $(@F))) \
 				    $(libof-$(<F)) \
 				    $(libof-$(@F)) \
 				    libc))
 
+module-cppflags-real = -include $(common-objpfx)libc-modules.h \
+		       -DIN_MODULE=MODULE_$(in-module)
+
+# We don't need libc-modules.h and the IN_MODULE definition for
+# shlib-version.v.i.
+module-cppflags = $(if $(filter $(@F),$(skip-module-cppflags)), \
+		       ,$(module-cppflags-real))
+
 # These are the variables that the implicit compilation rules use.
 # Note that we can't use -std=* in CPPFLAGS, because it overrides
 # the implicit -lang-asm and breaks cpp behavior for .S files--notably
 # it causes cpp to stop predefining __ASSEMBLER__.
 CPPFLAGS = $(config-extra-cppflags) $(CPPUNDEFS) $(CPPFLAGS-config) \
 	   $($(subdir)-CPPFLAGS) \
-	   $(+includes) $(defines) \
+	   $(+includes) $(defines) $(module-cppflags) \
 	   -include $(..)include/libc-symbols.h $(sysdep-CPPFLAGS) \
-	   $(CPPFLAGS-$(suffix $@)) -DIN_MODULE=MODULE_$(in-module) \
+	   $(CPPFLAGS-$(suffix $@)) \
 	   $(foreach lib,$(libof-$(basename $(@F))) \
 			 $(libof-$(<F)) $(libof-$(@F)),$(CPPFLAGS-$(lib))) \
 	   $(CPPFLAGS-$(<F)) $(CPPFLAGS-$(@F)) $(CPPFLAGS-$(basename $(@F)))
@@ -986,6 +1005,23 @@ endif
 postclean-generated += soversions.mk soversions.i \
 		       shlib-versions.v shlib-versions.v.i
 
+before-compile += $(common-objpfx)libc-modules.h
+ifeq ($(soversions.mk-done),t)
+# Generate a header with macro definitions for use with the IS_IN macro.
+# These are the possible values for the IN_MODULE macro defined when building
+# sources, to identify which module the translation unit is going to be built
+# into.
+$(common-objpfx)libc-modules.h: $(common-objpfx)libc-modules.stmp; @:
+$(common-objpfx)libc-modules.stmp: $(..)scripts/gen-libc-modules.awk \
+				   $(common-objpfx)soversions.i
+	$(AWK) -v buildlist="$(subst -,_,$(built-modules))" -f $^ > ${@:stmp=T}
+	$(move-if-change) ${@:stmp=T} ${@:stmp=h}
+	touch $@
+
+endif
+
+common-generated += libc-modules.h libc-modules.stmp
+
 # The name under which the run-time dynamic linker is installed.
 # We are currently going for the convention that `/lib/ld.so.1'
 # names the SVR4/ELF ABI-compliant dynamic linker.