Fix problem where gold cannot build .eh_frame_hdr from ld -r output.

When running ld -r on objects that have comdat groups, when gold
deduplicates a function in a comdat group, it removes the relocations
from the EH information that referred to the dropped copy of the function.
When running a final link using the result of the -r link, the missing
relocation cause it to fail to recognize the FDE for the dropped
function.

This patch improves gold's FDE scanning to take into account the
possibility that an FDE corresponds to a dropped function, and drops
that FDE as well.

Gnu ld, on the other hand, leaves the relocations in the ld -r output,
but makes them R_NONE with an r_sym field of 0. This was sufficient to
let both linkers recognize the FDE properly.

With this fix, if you do an ld -r with gold, then do the final link with
Gnu ld, the .eh_frame_hdr section will not be generated. To make it work
with Gnu ld, we would have to leave the R_NONE relocations in, but I
think it's better to drop the relocations entirely. I'd hope that if
you're doing a -r link with gold, you'll also do the final link with
gold.

gold/
	PR gold/19002
	* ehframe.cc (Eh_frame::read_fde): Check for dropped functions.
	* testsuite/Makefile.am (eh_test_2): New test.
	* testsuite/Makefile.in: Regenerate.
	* testsuite/eh_test_2.sh: New test script.
	* testsuite/eh_test_a.cc (bar): Make it comdat.
	* testsuite/eh_test_b.cc (bar): Add a duplicate copy.

5 files changed, 75 insertions, 2 deletions

diff --git a/gold/testsuite/Makefile.am b/gold/testsuite/Makefile.am
index f5528d1..fbaee16 100644
--- a/gold/testsuite/Makefile.am
+++ b/gold/testsuite/Makefile.am
@@ -388,6 +388,16 @@ eh_test_b.o: eh_test_b.cc
 eh_test: eh_test_a.o eh_test_b.o  gcctestdir/ld
 	$(CXXLINK_S) -Bgcctestdir/ eh_test_a.o eh_test_b.o
 
+check_SCRIPTS += eh_test_2.sh
+check_DATA += eh_test_2.sects
+MOSTLYCLEANFILES += eh_test_2.sects
+eh_test_r.o: eh_test_a.o eh_test_b.o gcctestdir/ld
+	gcctestdir/ld -r -o $@ eh_test_a.o eh_test_b.o
+eh_test_2: eh_test_r.o gcctestdir/ld
+	$(CXXLINK_S) -Bgcctestdir/ -Wl,--eh-frame-hdr eh_test_r.o
+eh_test_2.sects: eh_test_2
+	$(TEST_READELF) -SW $< >$@ 2>/dev/null
+
 if HAVE_STATIC
 check_PROGRAMS += basic_static_test
 basic_static_test: basic_test.o gcctestdir/ld
diff --git a/gold/testsuite/Makefile.in b/gold/testsuite/Makefile.in
index 988d6f7..1246504 100644
--- a/gold/testsuite/Makefile.in
+++ b/gold/testsuite/Makefile.in
@@ -72,7 +72,8 @@ check_PROGRAMS = $(am__EXEEXT_1) $(am__EXEEXT_2) $(am__EXEEXT_3) \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	icf_string_merge_test.sh \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	icf_sht_rel_addend_test.sh \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	merge_string_literals.sh \
-@GCC_TRUE@@NATIVE_LINKER_TRUE@	two_file_shared.sh weak_plt.sh
+@GCC_TRUE@@NATIVE_LINKER_TRUE@	eh_test_2.sh two_file_shared.sh \
+@GCC_TRUE@@NATIVE_LINKER_TRUE@	weak_plt.sh
 @GCC_TRUE@@NATIVE_LINKER_TRUE@am__append_3 = incremental_test.stdout \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	gc_comdat_test.stdout \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	gc_tls_test.stdout \
@@ -95,6 +96,7 @@ check_PROGRAMS = $(am__EXEEXT_1) $(am__EXEEXT_2) $(am__EXEEXT_3) \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	icf_string_merge_test.stdout \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	icf_sht_rel_addend_test.stdout \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	merge_string_literals.stdout \
+@GCC_TRUE@@NATIVE_LINKER_TRUE@	eh_test_2.sects \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	two_file_shared.dbg \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	weak_plt_shared.so
 @GCC_TRUE@@NATIVE_LINKER_TRUE@am__append_4 = incremental_test \
@@ -119,6 +121,7 @@ check_PROGRAMS = $(am__EXEEXT_1) $(am__EXEEXT_2) $(am__EXEEXT_3) \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	icf_string_merge_test \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	icf_sht_rel_addend_test \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	merge_string_literals \
+@GCC_TRUE@@NATIVE_LINKER_TRUE@	eh_test_2.sects \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	two_file_shared.dbg \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	alt/weak_undef_lib.so \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	libweak_undef_2.a
@@ -4496,6 +4499,8 @@ icf_sht_rel_addend_test.sh.log: icf_sht_rel_addend_test.sh
 	@p='icf_sht_rel_addend_test.sh'; $(am__check_pre) $(LOG_COMPILE) "$$tst" $(am__check_post)
 merge_string_literals.sh.log: merge_string_literals.sh
 	@p='merge_string_literals.sh'; $(am__check_pre) $(LOG_COMPILE) "$$tst" $(am__check_post)
+eh_test_2.sh.log: eh_test_2.sh
+	@p='eh_test_2.sh'; $(am__check_pre) $(LOG_COMPILE) "$$tst" $(am__check_post)
 two_file_shared.sh.log: two_file_shared.sh
 	@p='two_file_shared.sh'; $(am__check_pre) $(LOG_COMPILE) "$$tst" $(am__check_post)
 weak_plt.sh.log: weak_plt.sh
@@ -5295,6 +5300,12 @@ uninstall-am:
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	$(CXXCOMPILE) -O0 -c -o $@ $<
 @GCC_TRUE@@NATIVE_LINKER_TRUE@eh_test: eh_test_a.o eh_test_b.o  gcctestdir/ld
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	$(CXXLINK_S) -Bgcctestdir/ eh_test_a.o eh_test_b.o
+@GCC_TRUE@@NATIVE_LINKER_TRUE@eh_test_r.o: eh_test_a.o eh_test_b.o gcctestdir/ld
+@GCC_TRUE@@NATIVE_LINKER_TRUE@	gcctestdir/ld -r -o $@ eh_test_a.o eh_test_b.o
+@GCC_TRUE@@NATIVE_LINKER_TRUE@eh_test_2: eh_test_r.o gcctestdir/ld
+@GCC_TRUE@@NATIVE_LINKER_TRUE@	$(CXXLINK_S) -Bgcctestdir/ -Wl,--eh-frame-hdr eh_test_r.o
+@GCC_TRUE@@NATIVE_LINKER_TRUE@eh_test_2.sects: eh_test_2
+@GCC_TRUE@@NATIVE_LINKER_TRUE@	$(TEST_READELF) -SW $< >$@ 2>/dev/null
 @GCC_TRUE@@HAVE_STATIC_TRUE@@NATIVE_LINKER_TRUE@basic_static_test: basic_test.o gcctestdir/ld
 @GCC_TRUE@@HAVE_STATIC_TRUE@@NATIVE_LINKER_TRUE@	$(CXXLINK) -Bgcctestdir/ -static basic_test.o
 
diff --git a/gold/testsuite/eh_test_2.sh b/gold/testsuite/eh_test_2.sh
new file mode 100755
index 0000000..eb26854
--- /dev/null
+++ b/gold/testsuite/eh_test_2.sh
@@ -0,0 +1,37 @@
+#!/bin/sh
+
+# eh_test_2.sh -- check that .eh_frame_hdr is valid.
+
+# Copyright (C) 2016 Free Software Foundation, Inc.
+# Written by Cary Coutant <ccoutant@gmail.com>.
+
+# This file is part of gold.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
+# MA 02110-1301, USA.
+
+sections="eh_test_2.sects"
+
+hdr_section=`fgrep .eh_frame_hdr $sections`
+size_field=`echo $hdr_section | sed -e 's/\[//' | awk '{print $6;}'`
+size=`printf %d "0x$size_field"`
+
+if test "$size" -le 8; then
+  echo ".eh_frame_hdr section is too small:"
+  echo "$hdr_section"
+  exit 1
+fi
+
+exit 0
diff --git a/gold/testsuite/eh_test_a.cc b/gold/testsuite/eh_test_a.cc
index ad4bcc2..e3c8a16 100644
--- a/gold/testsuite/eh_test_a.cc
+++ b/gold/testsuite/eh_test_a.cc
@@ -1,4 +1,9 @@
+template<typename C>
 void
-bar()
+bar(C*)
 {
 }
+
+template
+void
+bar<int>(int*);
diff --git a/gold/testsuite/eh_test_b.cc b/gold/testsuite/eh_test_b.cc
index 50538df..3bf96e9 100644
--- a/gold/testsuite/eh_test_b.cc
+++ b/gold/testsuite/eh_test_b.cc
@@ -6,6 +6,16 @@ foo()
 {
 }
 
+template<typename C>
+void
+bar(C*)
+{
+}
+
+template
+void
+bar<int>(int*);
+
 int
 main()
 {