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[PATCH] Makeconfig: Move -Wl,-rpath-link options before library references


Previously, the -Wl,-rpath-link options came after the libraries
injected using LDLIBS-* variables on the link editor command line for
main programs.  As a result, it could happen that installed libraries
that reference glibc libraries used the installed glibc from the system
directories, instead of the glibc from the build tree.  This can lead to
link failures if the wrong version of libpthread.so.0 is used, for
instance, due to differences in the internal GLIBC_PRIVATE interfaces,
as seen with memusagestat and -lgd after commit
f9b645b4b0a10c43753296ce3fa40053fa44606a ("memusagestat: use local glibc
when linking [BZ #18465]").

The isolation is necessarily imperfect because these installed
libraries are linked against the installed glibc in the system
directories.  However, in most cases, the built glibc will be newer
than the installed glibc, and this link is permitted because of the
ABI backwards compatibility glibc provides.

(Note: This patch depends on "Makeconfig: Move $(CC) to +link command
variables".)

2019-04-25  Florian Weimer  <fweimer@redhat.com>

	Makeconfig: Move -Wl,-rpath-link options before library references.
	* Makeconfig (+link-pie, +link): Add $(link-libc-rpath-link).
	(link-libc): Remove $(link-libc-rpath-link).

diff --git a/Makeconfig b/Makeconfig
index 92c9b59bb5..76a5d41242 100644
--- a/Makeconfig
+++ b/Makeconfig
@@ -428,8 +428,8 @@ ifndef +link-pie
 	     $(link-extra-libs)
 +link-pie-after-libc = $(+postctorS) $(+postinit)
 define +link-pie
-$(CC) $(+link-pie-before-libc) $(rtld-LDFLAGS) $(link-extra-flags) \
-  $(link-libc) $(+link-pie-after-libc)
+$(CC) $(link-libc-rpath-link) $(+link-pie-before-libc) $(rtld-LDFLAGS) \
+  $(link-extra-flags) $(link-libc) $(+link-pie-after-libc)
 $(call after-link,$@)
 endef
 define +link-pie-tests
@@ -490,8 +490,8 @@ else  # not build-pie-default
 	      $(link-extra-libs)
 +link-after-libc = $(+postctor) $(+postinit)
 define +link
-$(CC) $(+link-before-libc) $(rtld-LDFLAGS) $(link-extra-flags) $(link-libc) \
-  $(+link-after-libc)
+$(CC) $(link-libc-rpath-link) $(+link-before-libc) $(rtld-LDFLAGS) \
+  $(link-extra-flags) $(link-libc) $(+link-after-libc)
 $(call after-link,$@)
 endef
 define +link-tests
@@ -552,6 +552,15 @@ ifeq (yes,$(build-shared))
 link-libc-rpath = -Wl,-rpath=$(rpath-link)
 link-libc-rpath-link = -Wl,-rpath-link=$(rpath-link)
 
+# For programs which are not tests, $(link-libc-rpath-link) is added
+# directly in $(+link), $(+link-pie) above, so that -Wl,-rpath-link
+# comes before the expansion of LDLIBS-* and affects libraries added
+# there.  For shared objects, -Wl,-rpath-link is added via
+# $(build-shlib-helper) and $(build-module-helper) in Makerules (also
+# before the expansion of LDLIBS-* variables).
+
+# Test use -Wl,-rpath instead of -Wl,-rpath-link for
+# build-hardcoded-path-in-tests.
 ifeq (yes,$(build-hardcoded-path-in-tests))
 link-libc-tests-rpath-link = $(link-libc-rpath)
 else
@@ -562,7 +571,7 @@ link-libc-before-gnulib = $(common-objpfx)libc.so$(libc.so-version) \
 			  $(common-objpfx)$(patsubst %,$(libtype.oS),c) \
 			  $(as-needed) $(elf-objpfx)ld.so \
 			  $(no-as-needed)
-link-libc = $(link-libc-rpath-link) $(link-libc-before-gnulib) $(gnulib)
+link-libc = $(link-libc-before-gnulib) $(gnulib)
 
 link-libc-tests-after-rpath-link = $(link-libc-before-gnulib) $(gnulib-tests)
 link-libc-tests = $(link-libc-tests-rpath-link) \


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