Add option --weak-unresolved-symbols to treat unresolved symbols as weak ref.

This patch adds option --weak-unresolved-symbols to treat unresolved symbols as
weak references.  This is helpful when we want the link to succeed with unresolved
symbols and the dynamic loader to not complain at run-time.  Option
--warn-unresolved-symbols lets the link succeed but could fail at run-time with
unresolved symbol warnings especially when the unresolved symbols have GOT entries
and dynamic relocations against them, like when -fPIE is used.

6 files changed, 69 insertions, 5 deletions

diff --git a/gold/ChangeLog b/gold/ChangeLog
index e736d33..c5b3093 100644
--- a/gold/ChangeLog
+++ b/gold/ChangeLog
@@ -1,3 +1,13 @@
+2015-04-23  Sriraman Tallam  <tmsriram@google.com>	
+	* options.h (--weak-unresolved-symbols): New option.
+	* symtab.cc (Symbol_table::sized_write_globals): Change symbol
+	binding to weak with new option.
+	* symtab.h (is_weak_undefined): Check for new option.
+	(is_strong_undefined): Check for new option.
+	* testsuite/Makefile.am (weak_unresolved_symbols_test): New test.
+	* testsuite/Makefile.in: Regenerate.
+	* testsuite/weak_unresolved_symbols_test.cc: New file.
+
 2015-04-20  Ian Coolidge  <icoolidge@google.com>
 
 	* symtab.cc (Symbol::should_add_dynsym_entry): Return true for
diff --git a/gold/options.h b/gold/options.h
index c1a5743..bb3bee6 100644
--- a/gold/options.h
+++ b/gold/options.h
@@ -1219,6 +1219,9 @@ class General_options
 		    options::TWO_DASHES, '\0',
 		    N_("Report unresolved symbols as errors"),
 		    NULL, true);
+  DEFINE_bool(weak_unresolved_symbols, options::TWO_DASHES, '\0', false,
+	      N_("Convert unresolved symbols to weak references"),
+	      NULL);
 
   DEFINE_bool(wchar_size_warning, options::TWO_DASHES, '\0', true, NULL,
 	      N_("(ARM only) Do not warn about objects with incompatible "
diff --git a/gold/symtab.cc b/gold/symtab.cc
index c197221..d2ed352 100644
--- a/gold/symtab.cc
+++ b/gold/symtab.cc
@@ -2920,6 +2920,13 @@ Symbol_table::sized_write_globals(const Stringpool* sympool,
       typename elfcpp::Elf_types<size>::Elf_Addr dynsym_value = sym_value;
       elfcpp::STB binding = sym->binding();
 
+      // If --weak-unresolved-symbols is set, change binding of unresolved
+      // global symbols to STB_WEAK.
+      if (parameters->options().weak_unresolved_symbols()
+	  && binding == elfcpp::STB_GLOBAL
+	  && sym->is_undefined())
+	binding = elfcpp::STB_WEAK;
+
       // If --no-gnu-unique is set, change STB_GNU_UNIQUE to STB_GLOBAL.
       if (binding == elfcpp::STB_GNU_UNIQUE
 	  && !parameters->options().gnu_unique())
diff --git a/gold/symtab.h b/gold/symtab.h
index 9413360..6f47c5e 100644
--- a/gold/symtab.h
+++ b/gold/symtab.h
@@ -526,7 +526,8 @@ class Symbol
   {
     return (this->is_undefined()
 	    && (this->binding() == elfcpp::STB_WEAK
-		|| this->is_undef_binding_weak()));
+		|| this->is_undef_binding_weak()
+		|| parameters->options().weak_unresolved_symbols()));
   }
 
   // Return whether this is a strong undefined symbol.
@@ -535,7 +536,8 @@ class Symbol
   {
     return (this->is_undefined()
 	    && this->binding() != elfcpp::STB_WEAK
-	    && !this->is_undef_binding_weak());
+	    && !this->is_undef_binding_weak()
+	    && !parameters->options().weak_unresolved_symbols());
   }
 
   // Return whether this is an absolute symbol.
diff --git a/gold/testsuite/Makefile.am b/gold/testsuite/Makefile.am
index c57b2b3..e47174d 100644
--- a/gold/testsuite/Makefile.am
+++ b/gold/testsuite/Makefile.am
@@ -533,6 +533,11 @@ pie_copyrelocs_shared_test.o: pie_copyrelocs_shared_test.cc
 pie_copyrelocs_shared_test.so: pie_copyrelocs_shared_test.o gcctestdir/ld
 	$(CXXLINK) -Bgcctestdir/ -shared pie_copyrelocs_shared_test.o
 
+check_PROGRAMS += weak_unresolved_symbols_test
+weak_unresolved_symbols_test_SOURCES = weak_unresolved_symbols_test.cc
+weak_unresolved_symbols_test_CXXFLAGS = -fPIE
+weak_unresolved_symbols_test_LDFLAGS = -Bgcctestdir/ -pie -Wl,--weak-unresolved-symbols
+
 check_SCRIPTS += two_file_shared.sh
 check_DATA += two_file_shared.dbg
 MOSTLYCLEANFILES += two_file_shared.dbg
diff --git a/gold/testsuite/Makefile.in b/gold/testsuite/Makefile.in
index 90c3054..4d7a54f 100644
--- a/gold/testsuite/Makefile.in
+++ b/gold/testsuite/Makefile.in
@@ -147,7 +147,8 @@ check_PROGRAMS = $(am__EXEEXT_1) $(am__EXEEXT_2) $(am__EXEEXT_3) \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	two_file_separate_shared_21_test \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	two_file_relocatable_test \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	two_file_pie_test \
-@GCC_TRUE@@NATIVE_LINKER_TRUE@	pie_copyrelocs_test
+@GCC_TRUE@@NATIVE_LINKER_TRUE@	pie_copyrelocs_test \
+@GCC_TRUE@@NATIVE_LINKER_TRUE@	weak_unresolved_symbols_test
 
 # The nonpic tests will fail on platforms which can not put non-PIC
 # code into shared libraries, so we just don't run them in that case.
@@ -842,7 +843,8 @@ libgoldtest_a_OBJECTS = $(am_libgoldtest_a_OBJECTS)
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	two_file_separate_shared_21_test$(EXEEXT) \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	two_file_relocatable_test$(EXEEXT) \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	two_file_pie_test$(EXEEXT) \
-@GCC_TRUE@@NATIVE_LINKER_TRUE@	pie_copyrelocs_test$(EXEEXT)
+@GCC_TRUE@@NATIVE_LINKER_TRUE@	pie_copyrelocs_test$(EXEEXT) \
+@GCC_TRUE@@NATIVE_LINKER_TRUE@	weak_unresolved_symbols_test$(EXEEXT)
 @FN_PTRS_IN_SO_WITHOUT_PIC_TRUE@@GCC_TRUE@@NATIVE_LINKER_TRUE@am__EXEEXT_9 = two_file_shared_1_nonpic_test$(EXEEXT) \
 @FN_PTRS_IN_SO_WITHOUT_PIC_TRUE@@GCC_TRUE@@NATIVE_LINKER_TRUE@	two_file_shared_2_nonpic_test$(EXEEXT) \
 @FN_PTRS_IN_SO_WITHOUT_PIC_TRUE@@GCC_TRUE@@NATIVE_LINKER_TRUE@	two_file_same_shared_nonpic_test$(EXEEXT) \
@@ -1966,6 +1968,17 @@ weak_undef_test_LINK = $(CXXLD) $(AM_CXXFLAGS) $(CXXFLAGS) \
 weak_undef_test_2_OBJECTS = $(am_weak_undef_test_2_OBJECTS)
 weak_undef_test_2_LINK = $(CXXLD) $(AM_CXXFLAGS) $(CXXFLAGS) \
 	$(weak_undef_test_2_LDFLAGS) $(LDFLAGS) -o $@
+@GCC_TRUE@@NATIVE_LINKER_TRUE@am_weak_unresolved_symbols_test_OBJECTS = weak_unresolved_symbols_test-weak_unresolved_symbols_test.$(OBJEXT)
+weak_unresolved_symbols_test_OBJECTS =  \
+	$(am_weak_unresolved_symbols_test_OBJECTS)
+weak_unresolved_symbols_test_LDADD = $(LDADD)
+weak_unresolved_symbols_test_DEPENDENCIES = libgoldtest.a ../libgold.a \
+	../../libiberty/libiberty.a $(am__DEPENDENCIES_1) \
+	$(am__DEPENDENCIES_1) $(am__DEPENDENCIES_1) \
+	$(am__DEPENDENCIES_1)
+weak_unresolved_symbols_test_LINK = $(CXXLD) \
+	$(weak_unresolved_symbols_test_CXXFLAGS) $(CXXFLAGS) \
+	$(weak_unresolved_symbols_test_LDFLAGS) $(LDFLAGS) -o $@
 DEFAULT_INCLUDES = -I.@am__isrc@ -I$(top_builddir)
 depcomp = $(SHELL) $(top_srcdir)/../depcomp
 am__depfiles_maybe = depfiles
@@ -2057,7 +2070,8 @@ SOURCES = $(libgoldtest_a_SOURCES) basic_pic_test.c basic_pie_test.c \
 	$(ver_test_8_SOURCES) $(ver_test_9_SOURCES) \
 	$(weak_alias_test_SOURCES) weak_plt.c $(weak_test_SOURCES) \
 	$(weak_undef_nonpic_test_SOURCES) $(weak_undef_test_SOURCES) \
-	$(weak_undef_test_2_SOURCES)
+	$(weak_undef_test_2_SOURCES) \
+	$(weak_unresolved_symbols_test_SOURCES)
 ETAGS = etags
 CTAGS = ctags
 am__tty_colors = \
@@ -2465,6 +2479,9 @@ LDADD = libgoldtest.a ../libgold.a ../../libiberty/libiberty.a $(LIBINTL) \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@pie_copyrelocs_test_CXXFLAGS = -fno-exceptions -fno-asynchronous-unwind-tables
 @GCC_TRUE@@NATIVE_LINKER_TRUE@pie_copyrelocs_test_LDFLAGS = -Bgcctestdir/ -Wl,-R,. -pie
 @GCC_TRUE@@NATIVE_LINKER_TRUE@pie_copyrelocs_test_LDADD = pie_copyrelocs_shared_test.so
+@GCC_TRUE@@NATIVE_LINKER_TRUE@weak_unresolved_symbols_test_SOURCES = weak_unresolved_symbols_test.cc
+@GCC_TRUE@@NATIVE_LINKER_TRUE@weak_unresolved_symbols_test_CXXFLAGS = -fPIE
+@GCC_TRUE@@NATIVE_LINKER_TRUE@weak_unresolved_symbols_test_LDFLAGS = -Bgcctestdir/ -pie -Wl,--weak-unresolved-symbols
 @FN_PTRS_IN_SO_WITHOUT_PIC_TRUE@@GCC_TRUE@@NATIVE_LINKER_TRUE@two_file_shared_1_nonpic_test_SOURCES = \
 @FN_PTRS_IN_SO_WITHOUT_PIC_TRUE@@GCC_TRUE@@NATIVE_LINKER_TRUE@	two_file_test_2.cc two_file_test_main.cc
 
@@ -3722,6 +3739,9 @@ weak_undef_test$(EXEEXT): $(weak_undef_test_OBJECTS) $(weak_undef_test_DEPENDENC
 weak_undef_test_2$(EXEEXT): $(weak_undef_test_2_OBJECTS) $(weak_undef_test_2_DEPENDENCIES) 
 	@rm -f weak_undef_test_2$(EXEEXT)
 	$(weak_undef_test_2_LINK) $(weak_undef_test_2_OBJECTS) $(weak_undef_test_2_LDADD) $(LIBS)
+weak_unresolved_symbols_test$(EXEEXT): $(weak_unresolved_symbols_test_OBJECTS) $(weak_unresolved_symbols_test_DEPENDENCIES) 
+	@rm -f weak_unresolved_symbols_test$(EXEEXT)
+	$(weak_unresolved_symbols_test_LINK) $(weak_unresolved_symbols_test_OBJECTS) $(weak_unresolved_symbols_test_LDADD) $(LIBS)
 
 mostlyclean-compile:
 	-rm -f *.$(OBJEXT)
@@ -3852,6 +3872,7 @@ distclean-compile:
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/weak_test.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/weak_undef_test.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/weak_undef_test_2.Po@am__quote@
+@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/weak_unresolved_symbols_test-weak_unresolved_symbols_test.Po@am__quote@
 
 .c.o:
 @am__fastdepCC_TRUE@	$(COMPILE) -MT $@ -MD -MP -MF $(DEPDIR)/$*.Tpo -c -o $@ $<
@@ -3979,6 +4000,20 @@ pie_copyrelocs_test-pie_copyrelocs_test.obj: pie_copyrelocs_test.cc
 @AMDEP_TRUE@@am__fastdepCXX_FALSE@	DEPDIR=$(DEPDIR) $(CXXDEPMODE) $(depcomp) @AMDEPBACKSLASH@
 @am__fastdepCXX_FALSE@	$(CXX) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS) $(pie_copyrelocs_test_CXXFLAGS) $(CXXFLAGS) -c -o pie_copyrelocs_test-pie_copyrelocs_test.obj `if test -f 'pie_copyrelocs_test.cc'; then $(CYGPATH_W) 'pie_copyrelocs_test.cc'; else $(CYGPATH_W) '$(srcdir)/pie_copyrelocs_test.cc'; fi`
 
+weak_unresolved_symbols_test-weak_unresolved_symbols_test.o: weak_unresolved_symbols_test.cc
+@am__fastdepCXX_TRUE@	$(CXX) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS) $(weak_unresolved_symbols_test_CXXFLAGS) $(CXXFLAGS) -MT weak_unresolved_symbols_test-weak_unresolved_symbols_test.o -MD -MP -MF $(DEPDIR)/weak_unresolved_symbols_test-weak_unresolved_symbols_test.Tpo -c -o weak_unresolved_symbols_test-weak_unresolved_symbols_test.o `test -f 'weak_unresolved_symbols_test.cc' || echo '$(srcdir)/'`weak_unresolved_symbols_test.cc
+@am__fastdepCXX_TRUE@	$(am__mv) $(DEPDIR)/weak_unresolved_symbols_test-weak_unresolved_symbols_test.Tpo $(DEPDIR)/weak_unresolved_symbols_test-weak_unresolved_symbols_test.Po
+@AMDEP_TRUE@@am__fastdepCXX_FALSE@	source='weak_unresolved_symbols_test.cc' object='weak_unresolved_symbols_test-weak_unresolved_symbols_test.o' libtool=no @AMDEPBACKSLASH@
+@AMDEP_TRUE@@am__fastdepCXX_FALSE@	DEPDIR=$(DEPDIR) $(CXXDEPMODE) $(depcomp) @AMDEPBACKSLASH@
+@am__fastdepCXX_FALSE@	$(CXX) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS) $(weak_unresolved_symbols_test_CXXFLAGS) $(CXXFLAGS) -c -o weak_unresolved_symbols_test-weak_unresolved_symbols_test.o `test -f 'weak_unresolved_symbols_test.cc' || echo '$(srcdir)/'`weak_unresolved_symbols_test.cc
+
+weak_unresolved_symbols_test-weak_unresolved_symbols_test.obj: weak_unresolved_symbols_test.cc
+@am__fastdepCXX_TRUE@	$(CXX) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS) $(weak_unresolved_symbols_test_CXXFLAGS) $(CXXFLAGS) -MT weak_unresolved_symbols_test-weak_unresolved_symbols_test.obj -MD -MP -MF $(DEPDIR)/weak_unresolved_symbols_test-weak_unresolved_symbols_test.Tpo -c -o weak_unresolved_symbols_test-weak_unresolved_symbols_test.obj `if test -f 'weak_unresolved_symbols_test.cc'; then $(CYGPATH_W) 'weak_unresolved_symbols_test.cc'; else $(CYGPATH_W) '$(srcdir)/weak_unresolved_symbols_test.cc'; fi`
+@am__fastdepCXX_TRUE@	$(am__mv) $(DEPDIR)/weak_unresolved_symbols_test-weak_unresolved_symbols_test.Tpo $(DEPDIR)/weak_unresolved_symbols_test-weak_unresolved_symbols_test.Po
+@AMDEP_TRUE@@am__fastdepCXX_FALSE@	source='weak_unresolved_symbols_test.cc' object='weak_unresolved_symbols_test-weak_unresolved_symbols_test.obj' libtool=no @AMDEPBACKSLASH@
+@AMDEP_TRUE@@am__fastdepCXX_FALSE@	DEPDIR=$(DEPDIR) $(CXXDEPMODE) $(depcomp) @AMDEPBACKSLASH@
+@am__fastdepCXX_FALSE@	$(CXX) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS) $(weak_unresolved_symbols_test_CXXFLAGS) $(CXXFLAGS) -c -o weak_unresolved_symbols_test-weak_unresolved_symbols_test.obj `if test -f 'weak_unresolved_symbols_test.cc'; then $(CYGPATH_W) 'weak_unresolved_symbols_test.cc'; else $(CYGPATH_W) '$(srcdir)/weak_unresolved_symbols_test.cc'; fi`
+
 ID: $(HEADERS) $(SOURCES) $(LISP) $(TAGS_FILES)
 	list='$(SOURCES) $(HEADERS) $(LISP) $(TAGS_FILES)'; \
 	unique=`for i in $$list; do \
@@ -4403,6 +4438,8 @@ two_file_pie_test.log: two_file_pie_test$(EXEEXT)
 	@p='two_file_pie_test$(EXEEXT)'; $(am__check_pre) $(LOG_COMPILE) "$$tst" $(am__check_post)
 pie_copyrelocs_test.log: pie_copyrelocs_test$(EXEEXT)
 	@p='pie_copyrelocs_test$(EXEEXT)'; $(am__check_pre) $(LOG_COMPILE) "$$tst" $(am__check_post)
+weak_unresolved_symbols_test.log: weak_unresolved_symbols_test$(EXEEXT)
+	@p='weak_unresolved_symbols_test$(EXEEXT)'; $(am__check_pre) $(LOG_COMPILE) "$$tst" $(am__check_post)
 two_file_shared_1_nonpic_test.log: two_file_shared_1_nonpic_test$(EXEEXT)
 	@p='two_file_shared_1_nonpic_test$(EXEEXT)'; $(am__check_pre) $(LOG_COMPILE) "$$tst" $(am__check_post)
 two_file_shared_2_nonpic_test.log: two_file_shared_2_nonpic_test$(EXEEXT)