diff --git a/Makeconfig b/Makeconfig
index cef0f06..5c6de39 100644
--- a/Makeconfig
+++ b/Makeconfig
@@ -813,6 +813,11 @@ endif	# $(+cflags) == ""
 # of many little headers in the include directory.
 libio-include = -I$(..)libio
 
+in-module = $(strip $(foreach lib,$(libof-$(basename $(@F))) $(libof-$(<F)) \
+				  $(libof-$(@F)),-DIN_MODULE=MODULE_$(lib)))
+
+module-def = $(if $(in-module),$(in-module),-DIN_MODULE=MODULE_libc)
+
 # 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
@@ -821,7 +826,7 @@ CPPFLAGS = $(config-extra-cppflags) $(CPPUNDEFS) $(CPPFLAGS-config) \
 	   $($(subdir)-CPPFLAGS) \
 	   $(+includes) $(defines) \
 	   -include $(..)include/libc-symbols.h $(sysdep-CPPFLAGS) \
-	   $(CPPFLAGS-$(suffix $@)) \
+	   $(CPPFLAGS-$(suffix $@)) $(module-def) \
 	   $(foreach lib,$(libof-$(basename $(@F))) \
 			 $(libof-$(<F)) $(libof-$(@F)),$(CPPFLAGS-$(lib))) \
 	   $(CPPFLAGS-$(<F)) $(CPPFLAGS-$(@F)) $(CPPFLAGS-$(basename $(@F)))
diff --git a/Makerules b/Makerules
index 6b30e8c..2736db7 100644
--- a/Makerules
+++ b/Makerules
@@ -1156,7 +1156,7 @@ xcheck: xtests
 
 all-nonlib = $(strip $(tests) $(xtests) $(test-srcs) $(test-extras) $(others))
 ifneq (,$(all-nonlib))
-cpp-srcs-left = $(all-nonlib:=.c) $(all-nonlib:=.cc)
+cpp-srcs-left = $(all-nonlib)
 lib := nonlib
 include $(patsubst %,$(..)cppflags-iterator.mk,$(cpp-srcs-left))
 endif
diff --git a/elf/Makefile b/elf/Makefile
index 25012cc..f7d384d 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -430,7 +430,8 @@ $(objpfx)ldconfig: $(ldconfig-modules:%=$(objpfx)%.o)
 
 SYSCONF-FLAGS := -D'SYSCONFDIR="$(sysconfdir)"'
 CFLAGS-ldconfig.c = $(SYSCONF-FLAGS) -D'LIBDIR="$(libdir)"' \
-		    -D'SLIBDIR="$(slibdir)"' -DIS_IN_ldconfig=1
+		    -D'SLIBDIR="$(slibdir)"' -DIS_IN_ldconfig=1 -DNOT_IN_libc=1
+libof-ldconfig = ldconfig
 CFLAGS-dl-cache.c = $(SYSCONF-FLAGS)
 CFLAGS-cache.c = $(SYSCONF-FLAGS)
 CFLAGS-rtld.c = $(SYSCONF-FLAGS)
@@ -438,6 +439,10 @@ CFLAGS-rtld.c = $(SYSCONF-FLAGS)
 CPPFLAGS-.os += $(if $(filter $(@F),$(patsubst %,%.os,$(all-rtld-routines))),\
 		     -DNOT_IN_libc=1 -DIS_IN_rtld=1 -DIN_LIB=rtld)
 
+cpp-srcs-left := $(all-rtld-routines:=.os)
+lib := rtld
+include $(patsubst %,$(..)cppflags-iterator.mk,$(cpp-srcs-left))
+
 test-modules = $(addprefix $(objpfx),$(addsuffix .so,$(strip $(modules-names))))
 generated += $(addsuffix .so,$(strip $(modules-names)))
 
diff --git a/elf/rtld-Rules b/elf/rtld-Rules
index 0a5d6af..4d78d90 100644
--- a/elf/rtld-Rules
+++ b/elf/rtld-Rules
@@ -138,6 +138,11 @@ ifdef rtld-depfiles
 -include $(rtld-depfiles)
 endif
 
+# Set libof-* for each routine.
+cpp-srcs-left := $(subst .os,,$(rtld-modules))
+lib := rtld
+include $(patsubst %,$(..)cppflags-iterator.mk,$(cpp-srcs-left))
+
 # This here is the whole point of all the shenanigans.
 rtld-CPPFLAGS := -DNOT_IN_libc=1 -DIS_IN_rtld=1 -DIN_LIB=rtld
 
diff --git a/extra-modules.mk b/extra-modules.mk
index c7ed850..9c2e4d2 100644
--- a/extra-modules.mk
+++ b/extra-modules.mk
@@ -6,4 +6,5 @@
 module := $(firstword $(extra-modules-left))
 extra-modules-left := $(filter-out $(module),$(extra-modules-left))
 
+libof-$(notdir $(module)) := extramodules
 CPPFLAGS-$(module).c += -DNOT_IN_libc
diff --git a/iconv/Makefile b/iconv/Makefile
index 48d17d7..8031a88 100644
--- a/iconv/Makefile
+++ b/iconv/Makefile
@@ -52,11 +52,12 @@ CFLAGS-gconv_cache.c += -DGCONV_DIR='"$(gconvdir)"'
 CFLAGS-gconv_conf.c = -DGCONV_PATH='"$(gconvdir)"'
 CFLAGS-iconvconfig.c = -DGCONV_PATH='"$(gconvdir)"' -DGCONV_DIR='"$(gconvdir)"'
 
-CPPFLAGS-iconv_charmap = -DNOT_IN_libc
-CPPFLAGS-linereader = -DNOT_IN_libc
-CPPFLAGS-strtab = -DNOT_IN_libc
-CPPFLAGS-charmap = -DNOT_IN_libc
-CPPFLAGS-charmap-dir = -DNOT_IN_libc
+CPPFLAGS-iconvprogs = -DNOT_IN_libc
+
+# Set libof-* for each routine.
+cpp-srcs-left := $(iconv_prog-modules) $(iconvconfig-modules)
+lib := iconvprogs
+include $(patsubst %,$(..)cppflags-iterator.mk,$(cpp-srcs-left))
 
 ifeq ($(run-built-tests),yes)
 xtests-special += $(objpfx)test-iconvconfig.out
diff --git a/iconvdata/Makefile b/iconvdata/Makefile
index 0a410a1..63ed612 100644
--- a/iconvdata/Makefile
+++ b/iconvdata/Makefile
@@ -211,6 +211,7 @@ $(objpfx)iconv-rules: Makefile
 	$(AWK) 'NR == 1 { \
 		  for (i = 1; i <= NF; i++) { \
 		    printf "%s-routines := %s\n", $$i, tolower($$i); \
+		    printf "libof-%s := iconvdata\n", tolower($$i); \
 		    printf "%s-map := gconv.map\n", $$i; \
 		  } \
 		}; \
@@ -273,6 +274,11 @@ endif
 
 include ../Rules
 
+# Set libof-* for each routine.
+cpp-srcs-left := $(modules) $(generated-modules)
+lib := iconvdata
+include $(patsubst %,$(..)cppflags-iterator.mk,$(cpp-srcs-left))
+
 tst-loading-ENV = MALLOC_TRACE=$(objpfx)tst-loading.mtrace
 $(objpfx)mtrace-tst-loading.out: $(objpfx)tst-loading.out
 	$(common-objpfx)malloc/mtrace $(objpfx)tst-loading.mtrace > $@; \
diff --git a/include/libc-modules.h b/include/libc-modules.h
new file mode 100644
index 0000000..d12fb90
--- /dev/null
+++ b/include/libc-modules.h
@@ -0,0 +1,37 @@
+#define MODULE_libc		1
+#define MODULE_libpthread	2
+#define MODULE_rtld		3
+#define MODULE_libdl		4
+#define MODULE_libm		5
+#define MODULE_iconvprogs	6
+#define MODULE_iconvdata	7
+#define MODULE_lddlibc4		8
+#define MODULE_locale_programs	9
+#define MODULE_memusagestat	10
+#define MODULE_libutil		12
+#define MODULE_libBrokenLocale	13
+#define MODULE_libmemusage	15
+#define MODULE_libresolv	16
+#define MODULE_libnss_db	17
+#define MODULE_libnss_files	18
+#define	MODULE_libnss_dns	19
+#define MODULE_libnss_compat	20
+#define MODULE_libnss_hesiod	21
+#define MODULE_libnss_nis	22
+#define MODULE_libnss_nisplus	23
+#define MODULE_libanl		24
+#define MODULE_librt		25
+#define MODULE_libSegFault	26
+#define MODULE_libthread_db	27
+#define MODULE_libcidn		28
+#define MODULE_libcrypt		29
+#define MODULE_libnsl		30
+#define MODULE_libpcprofile	31
+#define MODULE_librpcsvc	32
+#define MODULE_nscd		33
+#define MODULE_ldconfig 	34
+#define MODULE_libnldbl 	35
+
+/* Catch-all for test modules and other binaries.  */
+#define MODULE_nonlib		98
+#define MODULE_extramodules	99
diff --git a/include/libc-symbols.h b/include/libc-symbols.h
index d4ab1f3..131d7eb 100644
--- a/include/libc-symbols.h
+++ b/include/libc-symbols.h
@@ -20,6 +20,10 @@
 #ifndef _LIBC_SYMBOLS_H
 #define _LIBC_SYMBOLS_H	1
 
+#include "libc-modules.h"
+
+#define IS_IN(lib) (IN_MODULE == MODULE_##lib)
+
 /* This file's macros are included implicitly in the compilation of every
    file in the C library by -imacros.
 
@@ -468,7 +472,7 @@ for linking")
    If the function should be internal to multiple objects, say ld.so and
    libc.so, the best way is to use:
 
-   #if !defined NOT_IN_libc || defined IS_IN_rtld
+   #if IS_IN (libc) || IS_IN (rtld)
    hidden_proto (foo)
    #endif
 
@@ -584,7 +588,7 @@ for linking")
 # define libc_hidden_data_ver(local, name)
 #endif
 
-#ifdef IS_IN_rtld
+#if IS_IN (rtld)
 # define rtld_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 # define rtld_hidden_tls_proto(name, attrs...) hidden_tls_proto (name, ##attrs)
 # define rtld_hidden_def(name) hidden_def (name)
@@ -604,7 +608,7 @@ for linking")
 # define rtld_hidden_data_ver(local, name)
 #endif
 
-#ifdef IS_IN_libm
+#if IS_IN (libm)
 # define libm_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 # define libm_hidden_tls_proto(name, attrs...) hidden_tls_proto (name, ##attrs)
 # define libm_hidden_def(name) hidden_def (name)
@@ -624,7 +628,7 @@ for linking")
 # define libm_hidden_data_ver(local, name)
 #endif
 
-#ifdef IS_IN_libresolv
+#if IS_IN (libresolv)
 # define libresolv_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 # define libresolv_hidden_tls_proto(name, attrs...) \
   hidden_tls_proto (name, ##attrs)
@@ -645,7 +649,7 @@ for linking")
 # define libresolv_hidden_data_ver(local, name)
 #endif
 
-#ifdef IS_IN_librt
+#if IS_IN (librt)
 # define librt_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 # define librt_hidden_tls_proto(name, attrs...) \
   hidden_tls_proto (name, ##attrs)
@@ -666,7 +670,7 @@ for linking")
 # define librt_hidden_data_ver(local, name)
 #endif
 
-#ifdef IS_IN_libdl
+#if IS_IN (libdl)
 # define libdl_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 # define libdl_hidden_tls_proto(name, attrs...) \
   hidden_tls_proto (name, ##attrs)
@@ -687,7 +691,7 @@ for linking")
 # define libdl_hidden_data_ver(local, name)
 #endif
 
-#ifdef IS_IN_libnss_files
+#if IS_IN (libnss_files)
 # define libnss_files_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 # define libnss_files_hidden_tls_proto(name, attrs...) \
   hidden_tls_proto (name, ##attrs)
@@ -708,7 +712,7 @@ for linking")
 # define libnss_files_hidden_data_ver(local, name)
 #endif
 
-#ifdef IS_IN_libnsl
+#if IS_IN (libnsl)
 # define libnsl_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 # define libnsl_hidden_tls_proto(name, attrs...) \
   hidden_tls_proto (name, ##attrs)
@@ -729,7 +733,7 @@ for linking")
 # define libnsl_hidden_data_ver(local, name)
 #endif
 
-#ifdef IS_IN_libnss_nisplus
+#if IS_IN (libnss_nisplus)
 # define libnss_nisplus_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 # define libnss_nisplus_hidden_tls_proto(name, attrs...) \
   hidden_tls_proto (name, ##attrs)
@@ -758,7 +762,7 @@ for linking")
 # define HIDDEN_BUILTIN_JUMPTARGET(name) HIDDEN_JUMPTARGET(name)
 #endif
 
-#ifdef IS_IN_libutil
+#if IS_IN (libutil)
 # define libutil_hidden_proto(name, attrs...) hidden_proto (name, ##attrs)
 # define libutil_hidden_tls_proto(name, attrs...) \
   hidden_tls_proto (name, ##attrs)
diff --git a/locale/Makefile b/locale/Makefile
index e4c3878..5cd18e0 100644
--- a/locale/Makefile
+++ b/locale/Makefile
@@ -85,7 +85,7 @@ locale-CPPFLAGS = -DLOCALEDIR='"$(localedir)"' \
 		  -DLOCALE_ALIAS_PATH='"$(msgcatdir)"' \
 		  -Iprograms
 
-CPPFLAGS-locale-programs = -DLOCALE_PATH='$(localepath)' \
+CPPFLAGS-locale_programs = -DLOCALE_PATH='$(localepath)' \
 			   -DCHARMAP_PATH='"$(i18ndir)/charmaps"' \
 			   -DREPERTOIREMAP_PATH='"$(i18ndir)/repertoiremaps"' \
 			   -DLOCSRCDIR='"$(i18ndir)/locales"' \
@@ -96,7 +96,7 @@ CFLAGS-locfile.c = -Wno-write-strings -Wno-char-subscripts
 CFLAGS-charmap-dir.c = -Wno-write-strings
 
 # This makes sure -DNOT_IN_libc et al are passed for all these modules.
-cpp-srcs-left := $(addsuffix .c,$(localedef-modules) $(localedef-aux) \
-				$(locale-modules) $(lib-modules))
-lib := locale-programs
+cpp-srcs-left := $(localedef-modules) $(localedef-aux) $(locale-modules) \
+		 $(lib-modules)
+lib := locale_programs
 include $(patsubst %,$(..)cppflags-iterator.mk,$(cpp-srcs-left))
diff --git a/mach/Machrules b/mach/Machrules
index 8b35cf6..632f5f4 100644
--- a/mach/Machrules
+++ b/mach/Machrules
@@ -226,6 +226,7 @@ extra-libs += $(interface-library)
 extra-libs-others += $(interface-library)
 
 ifeq (yes,$(build-shared))
+
 interface.so = $(interface-library:=.so)
 
 # Depend on libc.so so a DT_NEEDED is generated in the shared objects.
diff --git a/malloc/Makefile b/malloc/Makefile
index 9e93523..fbfada2 100644
--- a/malloc/Makefile
+++ b/malloc/Makefile
@@ -89,6 +89,11 @@ endif
 do-memusagestat: $(objpfx)memusagestat
 
 memusagestat-modules = memusagestat
+
+cpp-srcs-left := $(memusagestat-modules)
+lib := memusagestat
+include $(patsubst %,$(..)cppflags-iterator.mk,$(cpp-srcs-left))
+
 $(objpfx)memusagestat: $(memusagestat-modules:%=$(objpfx)%.o)
 	$(LINK.o) -o $@ $^ $(libgd-LDFLAGS) -lgd -lpng -lz -lm
 
diff --git a/nscd/Makefile b/nscd/Makefile
index 639d87b..7ab4e9d 100644
--- a/nscd/Makefile
+++ b/nscd/Makefile
@@ -79,23 +79,22 @@ CFLAGS-nscd_gethst_r.c = -fexceptions
 CFLAGS-nscd_getai.c = -fexceptions
 CFLAGS-nscd_initgroups.c = -fexceptions
 
-CPPFLAGS-nonlib += -DIS_IN_nscd=1 -D_FORTIFY_SOURCE=2
+CPPFLAGS-nscd += -DIS_IN_nscd=1 -D_FORTIFY_SOURCE=2 -DNOT_IN_libc=1
 
 ifeq (yesyes,$(have-fpie)$(build-shared))
-CFLAGS-nonlib += $(pie-ccflag)
+CFLAGS-nscd += $(pie-ccflag)
 endif
 ifeq (yes,$(have-ssp))
-CFLAGS-nonlib += -fstack-protector
+CFLAGS-nscd += -fstack-protector
 endif
 
 ifeq (yesyes,$(have-fpie)$(build-shared))
 LDFLAGS-nscd = -Wl,-z,now
 endif
 
-# This makes sure CPPFLAGS-nonlib and CFLAGS-nonlib are passed
-# for all these modules.
-cpp-srcs-left := $(nscd-modules:=.c)
-lib := nonlib
+# Set libof-nscd.
+cpp-srcs-left := $(nscd-modules)
+lib := nscd
 include $(patsubst %,$(..)cppflags-iterator.mk,$(cpp-srcs-left))
 
 $(objpfx)nscd: $(nscd-modules:%=$(objpfx)%.o)
diff --git a/nss/Makefile b/nss/Makefile
index 1fa7f1f..7114d74 100644
--- a/nss/Makefile
+++ b/nss/Makefile
@@ -105,7 +105,8 @@ $(objpfx)makedb: $(makedb-modules:%=$(objpfx)%.o)
 $(inst_vardbdir)/Makefile: db-Makefile $(+force)
 	$(do-install)
 
-CFLAGS-nss_test1.c = -DNOT_IN_libc=1
+libof-nss_test1 = extramodules
+CPPFLAGS-nss_test1 = -DNOT_IN_libc=1
 $(objpfx)/libnss_test1.so: $(objpfx)nss_test1.os $(link-libc-deps)
 	$(build-module)
 ifdef libnss_test1.so-version
diff --git a/stdlib/Makefile b/stdlib/Makefile
index 9b2271b..da6e076 100644
--- a/stdlib/Makefile
+++ b/stdlib/Makefile
@@ -145,6 +145,7 @@ LDFLAGS-tst-putenv = $(no-as-needed)
 
 $(objpfx)tst-putenvmod.so: $(objpfx)tst-putenvmod.os $(link-libc-deps)
 	$(build-module)
+libof-tst-putenvmod = extramodules
 CFLAGS-tst-putenvmod.c = -DNOT_IN_libc=1
 
 $(objpfx)bug-getcontext: $(libm)
diff --git a/sysdeps/gnu/Makefile b/sysdeps/gnu/Makefile
index c05708d..b5b2cf0 100644
--- a/sysdeps/gnu/Makefile
+++ b/sysdeps/gnu/Makefile
@@ -29,6 +29,8 @@ ifeq ($(subdir),stdio-common)
 
 errlist-c = $(firstword $(wildcard $(addsuffix /errlist.c,$(sysdirs) .)))
 
+libof-errlist-compat = extramodules
+
 ifeq ($(build-shared),yes)
 $(objpfx)errlist-compat.c: $(errlist-c) $(..)sysdeps/gnu/errlist-compat.awk \
 			   $(common-objpfx)Versions.v.i $(before-compile)
diff --git a/sysdeps/s390/s390-64/Makefile b/sysdeps/s390/s390-64/Makefile
index fe5030e..ce4f0c5 100644
--- a/sysdeps/s390/s390-64/Makefile
+++ b/sysdeps/s390/s390-64/Makefile
@@ -28,6 +28,10 @@ s390x-iconv-modules = ISO-8859-1_CP037_Z900 UTF8_UTF16_Z9 UTF16_UTF32_Z9 UTF8_UT
 extra-modules-left += $(s390x-iconv-modules)
 include extra-module.mk
 
+cpp-srcs-left := $(foreach mod,$(s390x-iconv-modules),$($(mod)-routines))
+lib := iconvdata
+include $(patsubst %,$(..)cppflags-iterator.mk,$(cpp-srcs-left))
+
 extra-objs      += $(addsuffix .so, $(s390x-iconv-modules))
 install-others  += $(patsubst %, $(inst_gconvdir)/%.so, $(s390x-iconv-modules))
 
diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
index 9ad6d22..2d6d8bb 100644
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -178,6 +178,7 @@ ifeq ($(subdir),elf)
 sysdep-rtld-routines += dl-brk dl-sbrk dl-getcwd dl-openat64 dl-opendir \
 			dl-fxstatat64
 
+libof-lddlibc4 = lddlibc4
 CPPFLAGS-lddlibc4 += -DNOT_IN_libc
 
 others += pldd
