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[PATCH v2] Check for -z,defs, -z,relro, -fPIC, -fPIE before using them

From: Ulf Hermann <ulf dot hermann at qt dot io>
To: <elfutils-devel at sourceware dot org>
Date: Thu, 27 Apr 2017 18:01:58 +0200
Subject: [PATCH v2] Check for -z,defs, -z,relro, -fPIC, -fPIE before using them
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On windows those aren't needed because the link results are no ELF
files and all code is position independent anyway. gcc then complains
about them, which is in turn caught by -Werror.

Signed-off-by: Ulf Hermann <ulf.hermann@qt.io>
---
 ChangeLog            |  5 +++++
 backends/ChangeLog   |  4 ++++
 backends/Makefile.am |  4 ++--
 config/ChangeLog     |  4 ++++
 config/eu.am         |  4 ++--
 configure.ac         | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++--
 lib/ChangeLog        |  4 ++++
 lib/Makefile.am      |  2 +-
 libasm/ChangeLog     |  4 ++++
 libasm/Makefile.am   |  2 +-
 libcpu/ChangeLog     |  4 ++++
 libcpu/Makefile.am   |  2 +-
 libdw/ChangeLog      |  4 ++++
 libdw/Makefile.am    |  4 ++--
 libebl/ChangeLog     |  4 ++++
 libebl/Makefile.am   |  2 +-
 libelf/ChangeLog     |  4 ++++
 libelf/Makefile.am   |  6 +++---
 libgnu/Makefile.am   |  2 +-
 tests/ChangeLog      |  4 ++++
 tests/Makefile.am    |  4 ++--
 21 files changed, 111 insertions(+), 18 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 6fe525c..36c3cc7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
 2017-04-27  Ulf Hermann  <ulf.hermann@qt.io>
 
+	* configure.ac: Check if -fPIC, -fPIE, -Wl,-z,defs,
+	and -Wl,-z,relro are supported by the compiler.
+
+2017-04-27  Ulf Hermann  <ulf.hermann@qt.io>
+
 	* configure.ac: Drop checks for memrchr, rawmemchr, mempcpy, argp.
 
 2017-04-21  Ulf Hermann  <ulf.hermann@qt.io>
diff --git a/backends/ChangeLog b/backends/ChangeLog
index 594aa98..baeb7b9 100644
--- a/backends/ChangeLog
+++ b/backends/ChangeLog
@@ -1,3 +1,7 @@
+2017-04-27  Ulf Hermann <ulf.hermann@qt.io>
+
+	* Makefile.am: Use dso_LDFLAGS.
+
 2017-04-21  Ulf Hermann <ulf.hermann@qt.io>
 
 	* Makefile.am: Link backends against libgnu.a if requested.
diff --git a/backends/Makefile.am b/backends/Makefile.am
index 5dcb3e1..3e1992e 100644
--- a/backends/Makefile.am
+++ b/backends/Makefile.am
@@ -138,10 +138,10 @@ libebl_%.so libebl_%.map: libebl_%_pic.a $(libelf) $(libdw) $(libgnu)
 	@rm -f $(@:.so=.map)
 	$(AM_V_at)echo 'ELFUTILS_$(PACKAGE_VERSION) { global: $*_init; local: *; };' \
 	  > $(@:.so=.map)
-	$(AM_V_CCLD)$(LINK) -shared -o $(@:.map=.so) \
+	$(AM_V_CCLD)$(LINK) $(dso_LDFLAGS) -o $(@:.map=.so) \
 		-Wl,--whole-archive $< $(cpu_$*) -Wl,--no-whole-archive \
 		-Wl,--version-script,$(@:.so=.map) \
-		-Wl,-z,defs -Wl,--as-needed $(libelf) $(libdw) $(libgnu)
+		-Wl,--as-needed $(libelf) $(libdw) $(libgnu)
 	@$(textrel_check)
 
 libebl_i386.so: $(cpu_i386)
diff --git a/config/ChangeLog b/config/ChangeLog
index 756bab6..59569e3 100644
--- a/config/ChangeLog
+++ b/config/ChangeLog
@@ -1,3 +1,7 @@
+2017-04-27  Ulf Hermann  <ulf.hermann@qt.io>
+
+	* eu.am: Use fpic_CFLAGS.
+
 2017-04-21  Ulf Hermann  <ulf.hermann@qt.io>
 
 	* eu.am: Add $(top_srcdir)libgnu and $(top_builddir)/libgnu to -I if requested.
diff --git a/config/eu.am b/config/eu.am
index 11c2fec..bc8c767 100644
--- a/config/eu.am
+++ b/config/eu.am
@@ -89,14 +89,14 @@ endif
 
 %.os: %.c %.o
 if AMDEP
-	$(AM_V_CC)if $(COMPILE.os) -c -o $@ -fPIC $(DEFS.os) -MT $@ -MD -MP \
+	$(AM_V_CC)if $(COMPILE.os) -c -o $@ $(fpic_CFLAGS) $(DEFS.os) -MT $@ -MD -MP \
 	  -MF "$(DEPDIR)/$*.Tpo" `test -f '$<' || echo '$(srcdir)/'`$<; \
 	then cat "$(DEPDIR)/$*.Tpo" >> "$(DEPDIR)/$*.Po"; \
 	     rm -f "$(DEPDIR)/$*.Tpo"; \
 	else rm -f "$(DEPDIR)/$*.Tpo"; exit 1; \
 	fi
 else
-	$(AM_V_CC)$(COMPILE.os) -c -o $@ -fPIC $(DEFS.os) $<
+	$(AM_V_CC)$(COMPILE.os) -c -o $@ $(fpic_CFLAGS) $(DEFS.os) $<
 endif
 
 CLEANFILES = *.gcno *.gcda
diff --git a/configure.ac b/configure.ac
index a48b13e..107762f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -136,13 +136,65 @@ CFLAGS="$old_CFLAGS"])
 AS_IF([test "x$ac_cv_c99" != xyes],
       AC_MSG_ERROR([gcc with GNU99 support required]))
 
+AC_CACHE_CHECK([whether gcc supports -fPIC], ac_cv_fpic, [dnl
+save_CFLAGS="$CFLAGS"
+CFLAGS="$save_CFLAGS -fPIC -Werror"
+AC_COMPILE_IFELSE([AC_LANG_SOURCE()], ac_cv_fpic=yes, ac_cv_fpic=no)
+CFLAGS="$save_CFLAGS"
+])
+if test "$ac_cv_fpic" = "yes"; then
+	fpic_CFLAGS="-fPIC"
+else
+	fpic_CFLAGS=""
+fi
+AC_SUBST([fpic_CFLAGS])
+
+AC_CACHE_CHECK([whether gcc supports -fPIE], ac_cv_fpie, [dnl
+save_CFLAGS="$CFLAGS"
+CFLAGS="$save_CFLAGS -fPIE -Werror"
+AC_COMPILE_IFELSE([AC_LANG_SOURCE()], ac_cv_fpie=yes, ac_cv_fpie=no)
+CFLAGS="$save_CFLAGS"
+])
+if test "$ac_cv_fpie" = "yes"; then
+	fpie_CFLAGS="-fPIE"
+else
+	fpie_CFLAGS=""
+fi
+AC_SUBST([fpie_CFLAGS])
+
+dso_LDFLAGS="-shared"
+
+ZDEFS_LDFLAGS="-Wl,-z,defs"
+AC_CACHE_CHECK([whether gcc supports $ZDEFS_LDFLAGS], ac_cv_zdefs, [dnl
+save_LDFLAGS="$LDFLAGS"
+LDFLAGS="$ZDEFS_LDFLAGS $save_LDFLAGS"
+AC_LINK_IFELSE([AC_LANG_PROGRAM()], ac_cv_zdefs=yes, ac_cv_zdefs=no)
+LDFLAGS="$save_LDFLAGS"
+])
+if test "$ac_cv_zdefs" = "yes"; then
+	dso_LDFLAGS="$dso_LDFLAGS $ZDEFS_LDFLAGS"
+fi
+
+ZRELRO_LDFLAGS="-Wl,-z,relro"
+AC_CACHE_CHECK([whether gcc supports $ZRELRO_LDFLAGS], ac_cv_zrelro, [dnl
+save_LDFLAGS="$LDFLAGS"
+LDFLAGS="$ZRELRO_LDFLAGS $save_LDFLAGS"
+AC_LINK_IFELSE([AC_LANG_PROGRAM()], ac_cv_zrelro=yes, ac_cv_zrelro=no)
+LDFLAGS="$save_LDFLAGS"
+])
+if test "$ac_cv_zrelro" = "yes"; then
+	dso_LDFLAGS="$dso_LDFLAGS $ZRELRO_LDFLAGS"
+fi
+
+AC_SUBST([dso_LDFLAGS])
+
 AC_CACHE_CHECK([for __thread support], ac_cv_tls, [dnl
 # Use the same flags that we use for our DSOs, so the test is representative.
 # Some old compiler/linker/libc combinations fail some ways and not others.
 save_CFLAGS="$CFLAGS"
 save_LDFLAGS="$LDFLAGS"
-CFLAGS="-fPIC $CFLAGS"
-LDFLAGS="-shared -Wl,-z,defs,-z,relro $LDFLAGS"
+CFLAGS="$fpic_CFLAGS $CFLAGS"
+LDFLAGS="$dso_LDFLAGS $LDFLAGS"
 AC_LINK_IFELSE([dnl
 AC_LANG_PROGRAM([[#include <stdlib.h>
 #undef __thread
diff --git a/lib/ChangeLog b/lib/ChangeLog
index 82c009e..605b9b9 100644
--- a/lib/ChangeLog
+++ b/lib/ChangeLog
@@ -1,5 +1,9 @@
 2017-04-27  Ulf Hermann  <ulf.hermann@qt.io>
 
+	* Makefile.am: Use fpic_CFLAGS.
+
+2017-04-27  Ulf Hermann  <ulf.hermann@qt.io>
+
 	* system.h: Drop mempcpy replacement.
 	* xstrndup.c: Don't include system.h.
 
diff --git a/lib/Makefile.am b/lib/Makefile.am
index 7a65eb9..17d16d0 100644
--- a/lib/Makefile.am
+++ b/lib/Makefile.am
@@ -28,7 +28,7 @@
 ## not, see <http://www.gnu.org/licenses/>.
 ##
 include $(top_srcdir)/config/eu.am
-AM_CFLAGS += -fPIC
+AM_CFLAGS += $(fpic_CFLAGS)
 AM_CPPFLAGS += -I$(srcdir)/../libelf
 
 noinst_LIBRARIES = libeu.a
diff --git a/libasm/ChangeLog b/libasm/ChangeLog
index 80aa7de..971492a 100644
--- a/libasm/ChangeLog
+++ b/libasm/ChangeLog
@@ -1,5 +1,9 @@
 2017-02-27  Ulf Hermann  <ulf.hermann@qt.io>
 
+	* Makefile.am: Use dso_LDFLAGS.
+
+2017-02-27  Ulf Hermann  <ulf.hermann@qt.io>
+
 	* disasm_str.c: Don't include system.h
 
 2017-02-21  Ulf Hermann  <ulf.hermann@qt.io>
diff --git a/libasm/Makefile.am b/libasm/Makefile.am
index 8713070..a5fc9fc 100644
--- a/libasm/Makefile.am
+++ b/libasm/Makefile.am
@@ -65,7 +65,7 @@ endif
 
 libasm_so_SOURCES =
 libasm.so$(EXEEXT): libasm_pic.a libasm.map
-	$(AM_V_CCLD)$(LINK) -shared -o $@ -Wl,--whole-archive,$<,--no-whole-archive \
+	$(AM_V_CCLD)$(LINK) $(dso_LDFLAGS) -o $@ -Wl,--whole-archive,$<,--no-whole-archive \
 		-Wl,--version-script,$(srcdir)/libasm.map,--no-undefined \
 		-Wl,--soname,$@.$(VERSION) \
 		../libebl/libebl.a ../libelf/libelf.so ../libdw/libdw.so \
diff --git a/libcpu/ChangeLog b/libcpu/ChangeLog
index 9235b1b..ef5da58 100644
--- a/libcpu/ChangeLog
+++ b/libcpu/ChangeLog
@@ -1,3 +1,7 @@
+2017-02-27  Ulf Hermann  <ulf.hermann@qt.io>
+
+	* Makefile.am: Use fpic_CFLAGS.
+
 2017-02-21  Ulf Hermann  <ulf.hermann@qt.io>
 
 	* Makefile.am: Link gendis agaist libgnu.a if requested.
diff --git a/libcpu/Makefile.am b/libcpu/Makefile.am
index 30a6799..9ca0f43 100644
--- a/libcpu/Makefile.am
+++ b/libcpu/Makefile.am
@@ -30,7 +30,7 @@
 include $(top_srcdir)/config/eu.am
 AM_CPPFLAGS += -I$(srcdir)/../libelf -I$(srcdir)/../libebl \
 	    -I$(srcdir)/../libdw -I$(srcdir)/../libasm
-AM_CFLAGS += -fPIC -fdollars-in-identifiers
+AM_CFLAGS += $(fpic_CFLAGS) -fdollars-in-identifiers
 LEXCOMPILE = $(LEX) $(LFLAGS) $(AM_LFLAGS) -P$(<F:lex.l=)
 LEX_OUTPUT_ROOT = lex.$(<F:lex.l=)
 AM_YFLAGS = -p$(<F:parse.y=)
diff --git a/libdw/ChangeLog b/libdw/ChangeLog
index 6e11181..d15c861 100644
--- a/libdw/ChangeLog
+++ b/libdw/ChangeLog
@@ -1,5 +1,9 @@
 2017-02-27  Ulf Hermann  <ulf.hermann@qt.io>
 
+	* Makefile.am: Use fpic_CFLAGS and dso_LDFLAGS.
+
+2017-02-27  Ulf Hermann  <ulf.hermann@qt.io>
+
 	* Makefile.am: Remove argp_LDADD.
 
 2017-02-21  Ulf Hermann  <ulf.hermann@qt.io>
diff --git a/libdw/Makefile.am b/libdw/Makefile.am
index 8843062..7b69f6a 100644
--- a/libdw/Makefile.am
+++ b/libdw/Makefile.am
@@ -29,7 +29,7 @@
 ##
 include $(top_srcdir)/config/eu.am
 if BUILD_STATIC
-AM_CFLAGS += -fPIC
+AM_CFLAGS += $(fpic_CFLAGS)
 endif
 AM_CPPFLAGS += -I$(srcdir)/../libelf
 VERSION = 1
@@ -114,7 +114,7 @@ libdw.so$(EXEEXT): $(srcdir)/libdw.map libdw_pic.a ../libdwelf/libdwelf_pic.a \
 	  ../libelf/libelf.so
 # The rpath is necessary for libebl because its $ORIGIN use will
 # not fly in a setuid executable that links in libdw.
-	$(AM_V_CCLD)$(LINK) -shared -o $@ -Wl,--soname,$@.$(VERSION),-z,defs \
+	$(AM_V_CCLD)$(LINK) $(dso_LDFLAGS) -o $@ -Wl,--soname,$@.$(VERSION) \
 		-Wl,--enable-new-dtags,-rpath,$(pkglibdir) \
 		-Wl,--version-script,$<,--no-undefined \
 		-Wl,--whole-archive $(filter-out $<,$^) -Wl,--no-whole-archive\
diff --git a/libebl/ChangeLog b/libebl/ChangeLog
index 0605083..56b0421 100644
--- a/libebl/ChangeLog
+++ b/libebl/ChangeLog
@@ -1,5 +1,9 @@
 2017-04-27  Ulf Hermann  <ulf.hermann@qt.io>
 
+	* Makefile.am: Use fpic_CFLAGS.
+
+2017-04-27  Ulf Hermann  <ulf.hermann@qt.io>
+
 	* eblmachineflagname.c: Don't include system.h.
 	* eblopenbackend.c: Likewise.
 
diff --git a/libebl/Makefile.am b/libebl/Makefile.am
index 6f945eb..60d0e73 100644
--- a/libebl/Makefile.am
+++ b/libebl/Makefile.am
@@ -28,7 +28,7 @@
 ## not, see <http://www.gnu.org/licenses/>.
 ##
 include $(top_srcdir)/config/eu.am
-AM_CFLAGS += -fPIC
+AM_CFLAGS += $(fpic_CFLAGS)
 AM_CPPFLAGS += -I$(srcdir)/../libelf -I$(srcdir)/../libdw -I$(srcdir)/../libasm
 VERSION = 1
 LIBEBL_SUBDIR = @LIBEBL_SUBDIR@
diff --git a/libelf/ChangeLog b/libelf/ChangeLog
index 9165634..1c6cce2 100644
--- a/libelf/ChangeLog
+++ b/libelf/ChangeLog
@@ -1,5 +1,9 @@
 2017-04-27  Ulf Hermann  <ulf.hermann@qt.io>
 
+	* Makefile.am: Use fpic_CFLAGS and dso_LDFLAGS.
+
+2017-04-27  Ulf Hermann  <ulf.hermann@qt.io>
+
 	* elf_getarsym.c: Don't replace rawmemchr.
 	* elf_strptr.c: Don't replace memrchr.
 
diff --git a/libelf/Makefile.am b/libelf/Makefile.am
index d141c64..78d6853 100644
--- a/libelf/Makefile.am
+++ b/libelf/Makefile.am
@@ -29,7 +29,7 @@
 ##
 include $(top_srcdir)/config/eu.am
 if BUILD_STATIC
-AM_CFLAGS += -fPIC
+AM_CFLAGS += $(fpic_CFLAGS)
 endif
 GCC_INCLUDE = -I$(shell $(CC) -print-file-name=include)
 VERSION = 1
@@ -105,9 +105,9 @@ endif
 
 libelf_so_SOURCES =
 libelf.so$(EXEEXT): libelf_pic.a libelf.map
-	$(AM_V_CCLD)$(LINK) -shared -o $@ -Wl,--whole-archive,$<,--no-whole-archive \
+	$(AM_V_CCLD)$(LINK) $(dso_LDFLAGS) -o $@ -Wl,--whole-archive,$<,--no-whole-archive \
 		-Wl,--version-script,$(srcdir)/libelf.map,--no-undefined \
-		-Wl,--soname,$@.$(VERSION),-z,defs,-z,relro $(libelf_so_LDLIBS)
+		-Wl,--soname,$@.$(VERSION) $(libelf_so_LDLIBS)
 	@$(textrel_check)
 	$(AM_V_at)ln -fs $@ $@.$(VERSION)
 
diff --git a/libgnu/Makefile.am b/libgnu/Makefile.am
index c4a90e8..0d31e69 100644
--- a/libgnu/Makefile.am
+++ b/libgnu/Makefile.am
@@ -30,7 +30,7 @@
 
 # for eu-config.h
 AM_CPPFLAGS = -I$(top_srcdir)/lib
-AM_CFLAGS = -fPIC
+AM_CFLAGS = $(fpic_CFLAGS)
 noinst_LIBRARIES =
 MOSTLYCLEANFILES =
 MOSTLYCLEANDIRS =
diff --git a/tests/ChangeLog b/tests/ChangeLog
index d2a14c2..9d20341 100644
--- a/tests/ChangeLog
+++ b/tests/ChangeLog
@@ -1,5 +1,9 @@
 2017-04-27  Ulf Hermann <ulf.hermann@qt.io>
 
+	* Makefile.am: Use fpie_CFLAGS and fpic_CFLAGS.
+
+2017-04-27  Ulf Hermann <ulf.hermann@qt.io>
+
 	* Makefile.am: Drop argp_LDADD.
 	* elfstrmerge.c: Don't include system.h.
 
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 69d1fcd..7258069 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -468,7 +468,7 @@ dwfl_report_elf_align_LDADD = $(libdw) $(libgnu)
 varlocs_LDADD = $(libdw) $(libelf) $(libgnu)
 backtrace_LDADD = $(libdw) $(libelf) $(libgnu)
 # backtrace-child-biarch also uses those *_CFLAGS and *_LDLAGS variables:
-backtrace_child_CFLAGS = -fPIE
+backtrace_child_CFLAGS = $(fpie_CFLAGS)
 backtrace_child_LDFLAGS = -pie -pthread
 backtrace_child_biarch_SOURCES = backtrace-child.c
 backtrace_data_LDADD = $(libdw) $(libelf) $(libgnu)
@@ -479,7 +479,7 @@ debugaltlink_LDADD = $(libdw) $(libelf) $(libgnu)
 buildid_LDADD = $(libdw) $(libelf) $(libgnu)
 deleted_LDADD = ./deleted-lib.so $(libgnu)
 deleted_lib_so_LDFLAGS = -shared -rdynamic
-deleted_lib_so_CFLAGS = -fPIC -fasynchronous-unwind-tables
+deleted_lib_so_CFLAGS = $(fpic_CFLAGS) -fasynchronous-unwind-tables
 deleted_lib_so_LDADD = $(libgnu)
 aggregate_size_LDADD = $(libdw) $(libelf) $(libgnu)
 peel_type_LDADD = $(libdw) $(libelf) $(libgnu)
-- 
2.1.4
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