[PATCH] gnulib: Ensure all libraries are used when building gdb/gdbserver

Andrew Burgess andrew.burgess@embecosm.com
Mon Oct 5 16:51:34 GMT 2020 

An issue was reported here related to building GDB on MinGW:

  https://sourceware.org/pipermail/gdb/2020-September/048927.html

It was suggested here:

  https://sourceware.org/pipermail/gdb/2020-September/048931.html

that the solution might be to make use of $(LIB_GETRANDOM), a variable
defined in the gnulib makefile, when linking GDB.

In fact I think the issue is bigger than just LIB_GETRANDOM.  When
using the script binutils-gdb/gnulib/update-gnulib.sh to reimport
gnulib there is a lot of output from gnulib's gnulib-tool.  Part of
that output is this:

  You may need to use the following makefile variables when linking.
  Use them in <program>_LDADD when linking a program, or
  in <library>_a_LDFLAGS or <library>_la_LDFLAGS when linking a library.
    $(FREXPL_LIBM)
    $(FREXP_LIBM)
    $(INET_NTOP_LIB)
    $(LIBTHREAD)
    $(LIB_GETLOGIN)
    $(LIB_GETRANDOM)
    $(LIB_HARD_LOCALE)
    $(LIB_MBRTOWC)
    $(LIB_SETLOCALE_NULL)
    $(LTLIBINTL) when linking with libtool, $(LIBINTL) otherwise

What I think this is telling us is that we should be including the
value of all these variables on the link line for gdb and gdbserver.

The problem though is that these variables are define in gnulib's
makefile, but are not (necessarily) defined in GDB's makefile.

One solution would be to recreate the checks that gnulib performs in
order to recreate these variables in both gdb's and gdbserver's
makefile.  Though this shouldn't be too hard, most (if not all) of
these checks are in the form macros defined in m4 files in the gnulib
tree, so we could just reference these as needed.  However, in this
commit I propose a different solution.

Currently, in the top level makefile, we give gdb and gdbserver a
dependency on gnulib.  Once gnulib has finished building gdb and
gdbserver can start, these projects then have a hard coded (relative)
path to the compiled gnulib library in their makefiles.

In this commit I extend the gnulib makefile so that after building the
gnulib library we generate a makefile fragment that defines a number
of variables, these variables are:

LIBGNU: The path to the archive containing gnulib.  Can be used as a
       dependency as when this file changes gdb/gdbserver should be
       relinked.

LIBGNU_EXTRA_LIBS: A list of linker -l.... flags that should be
       included in the link line of gdb/gdbserver.  These are
       libraries that $(LIBGNU) depends on.

INCGNU: A list of -I.... include paths that should be passed to the
       compiler, these are where the gnulib headers can be found.

Now both gdb and gdbserver can include the makefile fragment and make
use of these variables.  As the makefile fragment is generated from
within gnulib's makefile, it has full access to the variable list
given above.

The generated makefile fragment relies on the variable GNULIB_BUILDDIR
being defined.  This is checked for in the fragment, and was already
defined in gdb and gdbserver.

gdb/ChangeLog:

	* Makefile.in: Include Makefile.gnulib.inc.  Don't define LIBGNU
	or INCGNU.  Make use of LIBGNU_EXTRA_LIBS when linking.

gdbserver/ChangeLog:

	* Makefile.in: Include Makefile.gnulib.inc.  Don't define LIBGNU
	or INCGNU.  Make use of LIBGNU_EXTRA_LIBS when linking.

gnulib/ChangeLog:

	* Makefile.am: Add rule to generate Makefile.gnulib.inc.
	* Makefile.in: Regenerate.
---
 gdb/ChangeLog         |  5 +++++
 gdb/Makefile.in       |  5 ++---
 gdbserver/ChangeLog   |  5 +++++
 gdbserver/Makefile.in | 11 +++++------
 gnulib/ChangeLog      |  5 +++++
 gnulib/Makefile.am    | 36 ++++++++++++++++++++++++++++++++++++
 gnulib/Makefile.in    | 40 ++++++++++++++++++++++++++++++++++++++--
 7 files changed, 96 insertions(+), 11 deletions(-)

diff --git a/gdb/Makefile.in b/gdb/Makefile.in
index dbede7a9cfc..18a426dc225 100644
--- a/gdb/Makefile.in
+++ b/gdb/Makefile.in
@@ -239,8 +239,7 @@ GDBFLAGS =
 
 # Helper code from gnulib.
 GNULIB_BUILDDIR = ../gnulib
-LIBGNU = $(GNULIB_BUILDDIR)/import/libgnu.a
-INCGNU = -I$(srcdir)/../gnulib/import -I$(GNULIB_BUILDDIR)/import
+include $(GNULIB_BUILDDIR)/Makefile.gnulib.inc
 
 SUPPORT = ../gdbsupport
 LIBSUPPORT = $(SUPPORT)/libgdbsupport.a
@@ -627,7 +626,7 @@ CLIBS = $(SIM) $(READLINE) $(OPCODES) $(LIBCTF) $(BFD) $(ZLIB) \
 	$(XM_CLIBS) $(GDBTKLIBS) \
 	@LIBS@ @GUILE_LIBS@ @PYTHON_LIBS@ \
 	$(LIBEXPAT) $(LIBLZMA) $(LIBBABELTRACE) $(LIBIPT) \
-	$(WIN32LIBS) $(LIBGNU) $(LIBICONV) \
+	$(WIN32LIBS) $(LIBGNU) $(LIBGNU_EXTRA_LIBS) $(LIBICONV) \
 	$(LIBMPFR) $(SRCHIGH_LIBS) $(LIBXXHASH) $(PTHREAD_LIBS) \
 	$(DEBUGINFOD_LIBS)
 CDEPS = $(NAT_CDEPS) $(SIM) $(BFD) $(READLINE_DEPS) $(CTF_DEPS) \
diff --git a/gdbserver/Makefile.in b/gdbserver/Makefile.in
index b0bad0cdb09..54b3f3becc4 100644
--- a/gdbserver/Makefile.in
+++ b/gdbserver/Makefile.in
@@ -111,8 +111,7 @@ ustinc = @ustinc@
 
 # gnulib
 GNULIB_BUILDDIR = ../gnulib
-LIBGNU = $(GNULIB_BUILDDIR)/import/libgnu.a
-INCGNU = -I$(srcdir)/../gnulib/import -I$(GNULIB_BUILDDIR)/import
+include $(GNULIB_BUILDDIR)/Makefile.gnulib.inc
 
 # Where is the INTL library?  Typically in ../intl.
 INTL = @LIBINTL@
@@ -352,16 +351,16 @@ gdbserver$(EXEEXT): $(sort $(OBS)) ${CDEPS} $(LIBGNU) $(LIBIBERTY) \
 	$(SILENCE) rm -f gdbserver$(EXEEXT)
 	$(ECHO_CXXLD) $(CC_LD) $(INTERNAL_CFLAGS) $(INTERNAL_LDFLAGS) \
 		-o gdbserver$(EXEEXT) $(OBS) $(GDBSUPPORT) $(LIBGNU) \
-		$(LIBIBERTY) $(INTL) $(GDBSERVER_LIBS) $(XM_CLIBS) \
-		$(WIN32APILIBS)
+		$(LIBGNU_EXTRA_LIBS) $(LIBIBERTY) $(INTL) \
+		$(GDBSERVER_LIBS) $(XM_CLIBS) $(WIN32APILIBS)
 
 gdbreplay$(EXEEXT): $(sort $(GDBREPLAY_OBS)) $(LIBGNU) $(LIBIBERTY) \
 		$(INTL_DEPS) $(GDBSUPPORT)
 	$(SILENCE) rm -f gdbreplay$(EXEEXT)
 	$(ECHO_CXXLD) $(CC_LD) $(INTERNAL_CFLAGS) $(INTERNAL_LDFLAGS) \
 		-o gdbreplay$(EXEEXT) $(GDBREPLAY_OBS) $(XM_CLIBS) \
-		$(GDBSUPPORT) $(LIBGNU) $(LIBIBERTY) $(INTL) \
-		$(WIN32APILIBS)
+		$(GDBSUPPORT) $(LIBGNU) $(LIBGNU_EXTRA_LIBS) \
+		$(LIBIBERTY) $(INTL) $(WIN32APILIBS)
 
 IPA_OBJS = \
 	alloc-ipa.o \
diff --git a/gnulib/Makefile.am b/gnulib/Makefile.am
index 3732e4d0dc2..29ac3f209e4 100644
--- a/gnulib/Makefile.am
+++ b/gnulib/Makefile.am
@@ -26,3 +26,39 @@
 MAKEOVERRIDES =
 
 SUBDIRS = import
+
+# Generate a makefile snippet that lists all of the libraries that
+# should be pulled in when linking against gnulib.  Both GDB and
+# GDBSERVER will include this snippet.
+#
+# The defined variables are:
+#
+# LIBGNU: The path to the archive containing gnulib.  Can be used as a
+#        dependency as when this file changes gdb/gdbserver should be
+#        relinked.
+#
+# LIBGNU_EXTRA_LIBS: A list of linker -l.... flags that should be
+#        included in the link line of gdb/gdbserver.  These are
+#        libraries that $(LIBGNU) depends on.
+#
+# INCGNU: A list of -I.... include paths that should be passed to the
+#        compiler, these are where the gnulib headers can be found.
+
+Makefile.gnulib.inc: $(builddir)/Makefile
+	$(AM_V_GEN)
+	@rm -f Makefile.gnulib.inc
+	@echo "ifndef GNULIB_BUILDDIR" > Makefile.gnulib.inc
+	@echo "\$$(error missing GNULIB_BUILDDIR)" >> Makefile.gnulib.inc
+	@echo "endif" >> Makefile.gnulib.inc
+	@echo "" >> Makefile.gnulib.inc
+	@echo "LIBGNU = \$$(GNULIB_BUILDDIR)/import/libgnu.a" \
+                        >> Makefile.gnulib.inc
+	@echo "LIBGNU_EXTRA_LIBS = $(FREXPL_LIBM) $(FREXP_LIBM) \
+                        $(INET_NTOP_LIB) $(LIBTHREAD) $(LIB_GETLOGIN) \
+                        $(LIB_GETRANDOM) $(LIB_HARD_LOCALE) $(LIB_MBRTOWC) \
+                        $(LIB_SETLOCALE_NULL)" | sed "s/ \+$$//" \
+                        >> Makefile.gnulib.inc
+	@echo "INCGNU = -I\$$(srcdir)/../gnulib/import -I\$$(GNULIB_BUILDDIR)/import" \
+                        >> Makefile.gnulib.inc
+
+all-local: Makefile.gnulib.inc
diff --git a/gnulib/Makefile.in b/gnulib/Makefile.in
index bdd3c3f3fbc..40ff899c943 100644
--- a/gnulib/Makefile.in
+++ b/gnulib/Makefile.in
@@ -1750,7 +1750,7 @@ distclean-tags:
 	-rm -f cscope.out cscope.in.out cscope.po.out cscope.files
 check-am: all-am
 check: check-recursive
-all-am: Makefile config.h
+all-am: Makefile config.h all-local
 installdirs: installdirs-recursive
 installdirs-am:
 install: install-recursive
@@ -1854,7 +1854,7 @@ uninstall-am:
 
 .MAKE: $(am__recursive_targets) all install-am install-strip
 
-.PHONY: $(am__recursive_targets) CTAGS GTAGS TAGS all all-am \
+.PHONY: $(am__recursive_targets) CTAGS GTAGS TAGS all all-am all-local \
 	am--refresh check check-am clean clean-cscope clean-generic \
 	cscope cscopelist-am ctags ctags-am distclean \
 	distclean-generic distclean-hdr distclean-tags dvi dvi-am html \
@@ -1870,6 +1870,42 @@ uninstall-am:
 .PRECIOUS: Makefile
 
 
+# Generate a makefile snippet that lists all of the libraries that
+# should be pulled in when linking against gnulib.  Both GDB and
+# GDBSERVER will include this snippet.
+#
+# The defined variables are:
+#
+# LIBGNU: The path to the archive containing gnulib.  Can be used as a
+#        dependency as when this file changes gdb/gdbserver should be
+#        relinked.
+#
+# LIBGNU_EXTRA_LIBS: A list of linker -l.... flags that should be
+#        included in the link line of gdb/gdbserver.  These are
+#        libraries that $(LIBGNU) depends on.
+#
+# INCGNU: A list of -I.... include paths that should be passed to the
+#        compiler, these are where the gnulib headers can be found.
+
+Makefile.gnulib.inc: $(builddir)/Makefile
+	$(AM_V_GEN)
+	@rm -f Makefile.gnulib.inc
+	@echo "ifndef GNULIB_BUILDDIR" > Makefile.gnulib.inc
+	@echo "\$$(error missing GNULIB_BUILDDIR)" >> Makefile.gnulib.inc
+	@echo "endif" >> Makefile.gnulib.inc
+	@echo "" >> Makefile.gnulib.inc
+	@echo "LIBGNU = \$$(GNULIB_BUILDDIR)/import/libgnu.a" \
+                        >> Makefile.gnulib.inc
+	@echo "LIBGNU_EXTRA_LIBS = $(FREXPL_LIBM) $(FREXP_LIBM) \
+                        $(INET_NTOP_LIB) $(LIBTHREAD) $(LIB_GETLOGIN) \
+                        $(LIB_GETRANDOM) $(LIB_HARD_LOCALE) $(LIB_MBRTOWC) \
+                        $(LIB_SETLOCALE_NULL)" | sed "s/ \+$$//" \
+                        >> Makefile.gnulib.inc
+	@echo "INCGNU = -I\$$(srcdir)/../gnulib/import -I\$$(GNULIB_BUILDDIR)/import" \
+                        >> Makefile.gnulib.inc
+
+all-local: Makefile.gnulib.inc
+
 # Tell versions [3.59,3.63) of GNU make to not export all variables.
 # Otherwise a system limit (for SysV at least) may be exceeded.
 .NOEXPORT:
-- 
2.25.4

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