Add heuristics for undefined symbol warnings.

gold/gold.cc

@@ -286,7 +286,7 @@ queue_final_tasks(const General_options& options,
   // Queue a task to write out the symbol table.
   final_blocker->add_blocker();
   workqueue->queue(new Write_symbols_task(symtab,
-					  input_objects->target(),
+					  input_objects,
 					  layout->sympool(),
 					  layout->dynpool(),
 					  of,

gold/i386.cc

@@ -100,6 +100,11 @@ class Target_i386 : public Sized_target<32, false>
   std::string
   do_code_fill(off_t length);
 
+  // Return whether SYM is defined by the ABI.
+  bool
+  do_is_defined_by_abi(Symbol* sym) const
+  { return strcmp(sym->name(), "___tls_get_addr") == 0; }
+
   // Return the size of the GOT section.
   off_t
   got_size()

gold/layout.cc

@@ -1928,8 +1928,8 @@ Write_symbols_task::locks(Workqueue* workqueue)
 void
 Write_symbols_task::run(Workqueue*)
 {
-  this->symtab_->write_globals(this->target_, this->sympool_, this->dynpool_,
-			       this->of_);
+  this->symtab_->write_globals(this->input_objects_, this->sympool_,
+			       this->dynpool_, this->of_);
 }
 
 // Write_after_input_sections_task methods.

gold/layout.h

@@ -506,11 +506,12 @@ class Write_data_task : public Task
 class Write_symbols_task : public Task
 {
  public:
-  Write_symbols_task(const Symbol_table* symtab, const Target* target,
+  Write_symbols_task(const Symbol_table* symtab,
+		     const Input_objects* input_objects,
 		     const Stringpool* sympool, const Stringpool* dynpool,
 		     Output_file* of, Task_token* final_blocker)
-    : symtab_(symtab), target_(target), sympool_(sympool), dynpool_(dynpool),
-      of_(of), final_blocker_(final_blocker)
+    : symtab_(symtab), input_objects_(input_objects), sympool_(sympool),
+      dynpool_(dynpool), of_(of), final_blocker_(final_blocker)
   { }
 
   // The standard Task methods.
@@ -526,7 +527,7 @@ class Write_symbols_task : public Task
 
  private:
   const Symbol_table* symtab_;
-  const Target* target_;
+  const Input_objects* input_objects_;
   const Stringpool* sympool_;
   const Stringpool* dynpool_;
   Output_file* of_;

gold/object.cc

@@ -25,6 +25,7 @@
 #include <cerrno>
 #include <cstring>
 #include <cstdarg>
+#include "libiberty.h"
 
 #include "target-select.h"
 #include "dwarf_reader.h"
@@ -1062,9 +1063,10 @@ Input_objects::add_object(Object* obj)
     {
       // See if this is a duplicate SONAME.
       Dynobj* dynobj = static_cast<Dynobj*>(obj);
+      const char* soname = dynobj->soname();
 
       std::pair<Unordered_set<std::string>::iterator, bool> ins =
-	this->sonames_.insert(dynobj->soname());
+	this->sonames_.insert(soname);
       if (!ins.second)
 	{
 	  // We have already seen a dynamic object with this soname.
@@ -1072,6 +1074,19 @@ Input_objects::add_object(Object* obj)
 	}
 
       this->dynobj_list_.push_back(dynobj);
+
+      // If this is -lc, remember the directory in which we found it.
+      // We use this when issuing warnings about undefined symbols: as
+      // a heuristic, we don't warn about system libraries found in
+      // the same directory as -lc.
+      if (strncmp(soname, "libc.so", 7) == 0)
+	{
+	  const char* object_name = dynobj->name().c_str();
+	  const char* base = lbasename(object_name);
+	  if (base != object_name)
+	    this->system_library_directory_.assign(object_name,
+						   base - 1 - object_name);
+	}
     }
 
   set_parameters_size_and_endianness(target->get_size(),
@@ -1080,6 +1095,17 @@ Input_objects::add_object(Object* obj)
   return true;
 }
 
+// Return whether an object was found in the system library directory.
+
+bool
+Input_objects::found_in_system_library_directory(const Object* object) const
+{
+  return (!this->system_library_directory_.empty()
+	  && object->name().compare(0,
+				    this->system_library_directory_.size(),
+				    this->system_library_directory_) == 0);
+}
+
 // For each dynamic object, record whether we've seen all of its
 // explicit dependencies.
 

gold/object.h

@@ -930,7 +930,8 @@ class Input_objects
 {
  public:
   Input_objects()
-    : relobj_list_(), dynobj_list_(), target_(NULL), sonames_()
+    : relobj_list_(), dynobj_list_(), target_(NULL), sonames_(),
+      system_library_directory_()
   { }
 
   // The type of the list of input relocateable objects.
@@ -956,6 +957,11 @@ class Input_objects
   void
   check_dynamic_dependencies() const;
 
+  // Return whether an object was found in the system library
+  // directory.
+  bool
+  found_in_system_library_directory(const Object*) const;
+
   // Iterate over all regular objects.
 
   Relobj_iterator
@@ -998,6 +1004,8 @@ class Input_objects
   Target* target_;
   // SONAMEs that we have seen.
   Unordered_set<std::string> sonames_;
+  // The directory in which we find the libc.so.
+  std::string system_library_directory_;
 };
 
 // Some of the information we pass to the relocation routines.  We

gold/options.cc

@@ -483,7 +483,7 @@ General_options::General_options()
     output_file_name_("a.out"),
     is_relocatable_(false),
     strip_(STRIP_NONE),
-    allow_shlib_undefined_(true),
+    allow_shlib_undefined_(false),
     symbolic_(false),
     detect_odr_violations_(false),
     create_eh_frame_hdr_(false),

gold/symtab.cc

@@ -1524,7 +1524,8 @@ Symbol_table::sized_finalize(unsigned index, off_t off, Stringpool* pool)
 // Write out the global symbols.
 
 void
-Symbol_table::write_globals(const Target* target, const Stringpool* sympool,
+Symbol_table::write_globals(const Input_objects* input_objects,
+			    const Stringpool* sympool,
 			    const Stringpool* dynpool, Output_file* of) const
 {
   if (parameters->get_size() == 32)
@@ -1532,7 +1533,8 @@ Symbol_table::write_globals(const Target* target, const Stringpool* sympool,
       if (parameters->is_big_endian())
 	{
 #ifdef HAVE_TARGET_32_BIG
-	  this->sized_write_globals<32, true>(target, sympool, dynpool, of);
+	  this->sized_write_globals<32, true>(input_objects, sympool,
+					      dynpool, of);
 #else
 	  gold_unreachable();
 #endif
@@ -1540,7 +1542,8 @@ Symbol_table::write_globals(const Target* target, const Stringpool* sympool,
       else
 	{
 #ifdef HAVE_TARGET_32_LITTLE
-	  this->sized_write_globals<32, false>(target, sympool, dynpool, of);
+	  this->sized_write_globals<32, false>(input_objects, sympool,
+					       dynpool, of);
 #else
 	  gold_unreachable();
 #endif
@@ -1551,7 +1554,8 @@ Symbol_table::write_globals(const Target* target, const Stringpool* sympool,
       if (parameters->is_big_endian())
 	{
 #ifdef HAVE_TARGET_64_BIG
-	  this->sized_write_globals<64, true>(target, sympool, dynpool, of);
+	  this->sized_write_globals<64, true>(input_objects, sympool,
+					      dynpool, of);
 #else
 	  gold_unreachable();
 #endif
@@ -1559,7 +1563,8 @@ Symbol_table::write_globals(const Target* target, const Stringpool* sympool,
       else
 	{
 #ifdef HAVE_TARGET_64_LITTLE
-	  this->sized_write_globals<64, false>(target, sympool, dynpool, of);
+	  this->sized_write_globals<64, false>(input_objects, sympool,
+					       dynpool, of);
 #else
 	  gold_unreachable();
 #endif
@@ -1573,11 +1578,13 @@ Symbol_table::write_globals(const Target* target, const Stringpool* sympool,
 
 template<int size, bool big_endian>
 void
-Symbol_table::sized_write_globals(const Target* target,
+Symbol_table::sized_write_globals(const Input_objects* input_objects,
 				  const Stringpool* sympool,
 				  const Stringpool* dynpool,
 				  Output_file* of) const
 {
+  const Target* const target = input_objects->target();
+
   const int sym_size = elfcpp::Elf_sizes<size>::sym_size;
   unsigned int index = this->first_global_index_;
   const off_t oview_size = this->output_count_ * sym_size;
@@ -1599,25 +1606,8 @@ Symbol_table::sized_write_globals(const Target* target,
     {
       Sized_symbol<size>* sym = static_cast<Sized_symbol<size>*>(p->second);
 
-      // Optionally check for unresolved symbols in shared libraries.
-      // This is controlled by the --allow-shlib-undefined option.  We
-      // only warn about libraries for which we have seen all the
-      // DT_NEEDED entries.  We don't try to track down DT_NEEDED
-      // entries which were not seen in this link.  If we didn't see a
-      // DT_NEEDED entry, we aren't going to be able to reliably
-      // report whether the symbol is undefined.
-      if (sym->source() == Symbol::FROM_OBJECT
-          && sym->object()->is_dynamic()
-          && sym->shndx() == elfcpp::SHN_UNDEF
-	  && sym->binding() != elfcpp::STB_WEAK
-	  && !parameters->allow_shlib_undefined())
-	{
-	  // A very ugly cast.
-	  Dynobj* dynobj = static_cast<Dynobj*>(sym->object());
-	  if (!dynobj->has_unknown_needed_entries())
-	    gold_error(_("%s: undefined reference to '%s'"),
-		       sym->object()->name().c_str(), sym->name());
-	}
+      // Possibly warn about unresolved symbols in shared libraries.
+      this->warn_about_undefined_dynobj_symbol(input_objects, sym);
 
       unsigned int sym_index = sym->symtab_index();
       unsigned int dynsym_index;
@@ -1749,6 +1739,42 @@ Symbol_table::sized_write_symbol(
   osym.put_st_shndx(shndx);
 }
 
+// Check for unresolved symbols in shared libraries.  This is
+// controlled by the --allow-shlib-undefined option.
+
+// We only warn about libraries for which we have seen all the
+// DT_NEEDED entries.  We don't try to track down DT_NEEDED entries
+// which were not seen in this link.  If we didn't see a DT_NEEDED
+// entry, we aren't going to be able to reliably report whether the
+// symbol is undefined.
+
+// We also don't warn about libraries found in the system library
+// directory (the directory were we find libc.so); we assume that
+// those libraries are OK.  This heuristic avoids problems in
+// GNU/Linux, in which -ldl can have undefined references satisfied by
+// ld-linux.so.
+
+inline void
+Symbol_table::warn_about_undefined_dynobj_symbol(
+    const Input_objects* input_objects,
+    Symbol* sym) const
+{
+  if (sym->source() == Symbol::FROM_OBJECT
+      && sym->object()->is_dynamic()
+      && sym->shndx() == elfcpp::SHN_UNDEF
+      && sym->binding() != elfcpp::STB_WEAK
+      && !parameters->allow_shlib_undefined()
+      && !input_objects->target()->is_defined_by_abi(sym)
+      && !input_objects->found_in_system_library_directory(sym->object()))
+    {
+      // A very ugly cast.
+      Dynobj* dynobj = static_cast<Dynobj*>(sym->object());
+      if (!dynobj->has_unknown_needed_entries())
+	gold_error(_("%s: undefined reference to '%s'"),
+		   sym->object()->name().c_str(), sym->name());
+    }
+}
+
 // Write out a section symbol.  Return the update offset.
 
 void

gold/symtab.h

@@ -46,6 +46,7 @@ class Dynobj;
 template<int size, bool big_endian>
 class Sized_dynobj;
 class Versions;
+class Input_objects;
 class Output_data;
 class Output_section;
 class Output_segment;
@@ -1055,7 +1056,7 @@ class Symbol_table
 
   // Write out the global symbols.
   void
-  write_globals(const Target*, const Stringpool*, const Stringpool*,
+  write_globals(const Input_objects*, const Stringpool*, const Stringpool*,
 		Output_file*) const;
 
   // Write out a section symbol.  Return the updated offset.
@@ -1177,8 +1178,8 @@ class Symbol_table
   // Write globals specialized for size and endianness.
   template<int size, bool big_endian>
   void
-  sized_write_globals(const Target*, const Stringpool*, const Stringpool*,
-		      Output_file*) const;
+  sized_write_globals(const Input_objects*, const Stringpool*,
+		      const Stringpool*, Output_file*) const;
 
   // Write out a symbol to P.
   template<int size, bool big_endian>
@@ -1189,6 +1190,10 @@ class Symbol_table
 		     const Stringpool*, unsigned char* p
                      ACCEPT_SIZE_ENDIAN) const;
 
+  // Possibly warn about an undefined symbol from a dynamic object.
+  void
+  warn_about_undefined_dynobj_symbol(const Input_objects*, Symbol*) const;
+
   // Write out a section symbol, specialized for size and endianness.
   template<int size, bool big_endian>
   void

gold/target.h

@@ -137,6 +137,12 @@ class Target
   code_fill(off_t length)
   { return this->do_code_fill(length); }
 
+  // Return whether SYM is known to be defined by the ABI.  This is
+  // used to avoid inappropriate warnings about undefined symbols.
+  bool
+  is_defined_by_abi(Symbol* sym) const
+  { return this->do_is_defined_by_abi(sym); }
+
  protected:
   // This struct holds the constant information for a child class.  We
   // use a struct to avoid the overhead of virtual function calls for
@@ -188,6 +194,11 @@ class Target
   do_code_fill(off_t)
   { gold_unreachable(); }
 
+  // Virtual function which may be implemented by the child class.
+  virtual bool
+  do_is_defined_by_abi(Symbol*) const
+  { return false; }
+
  private:
   Target(const Target&);
   Target& operator=(const Target&);

gold/testsuite/Makefile.am

@@ -30,12 +30,9 @@ if GCC
 
 if NATIVE_LINKER
 
-TESTS += debug_msg.sh
+TESTS += debug_msg.sh undef_symbol.sh
 
-check_DATA += debug_msg.err
-
-# TESTS += undef_symbol.sh
-# check_DATA +=undef_symbol.err
+check_DATA += debug_msg.err undef_symbol.err
 
 NATIVE_PROGS = \
 	constructor_test \

gold/testsuite/Makefile.in

@@ -42,8 +42,8 @@ POST_UNINSTALL = :
 build_triplet = @build@
 host_triplet = @host@
 target_triplet = @target@
-@GCC_TRUE@@NATIVE_LINKER_TRUE@am__append_1 = debug_msg.sh
-@GCC_TRUE@@NATIVE_LINKER_TRUE@am__append_2 = debug_msg.err
+@GCC_TRUE@@NATIVE_LINKER_TRUE@am__append_1 = debug_msg.sh undef_symbol.sh
+@GCC_TRUE@@NATIVE_LINKER_TRUE@am__append_2 = debug_msg.err undef_symbol.err
 @FN_PTRS_IN_SO_WITHOUT_PIC_TRUE@@GCC_TRUE@@NATIVE_LINKER_TRUE@am__append_3 = \
 @FN_PTRS_IN_SO_WITHOUT_PIC_TRUE@@GCC_TRUE@@NATIVE_LINKER_TRUE@	two_file_shared_1_nonpic_test \
 @FN_PTRS_IN_SO_WITHOUT_PIC_TRUE@@GCC_TRUE@@NATIVE_LINKER_TRUE@	two_file_shared_2_nonpic_test \
@@ -573,9 +573,6 @@ INCLUDES = \
 check_SCRIPTS = debug_msg.sh
 check_DATA = $(am__append_2)
 TESTS = object_unittest $(am__append_1) $(NATIVE_TESTING)
-
-# TESTS += undef_symbol.sh
-# check_DATA +=undef_symbol.err
 @GCC_TRUE@@NATIVE_LINKER_TRUE@NATIVE_PROGS = constructor_test \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	constructor_static_test \
 @GCC_TRUE@@NATIVE_LINKER_TRUE@	two_file_test \

gold/x86_64.cc

@@ -113,6 +113,11 @@ class Target_x86_64 : public Sized_target<64, false>
   std::string
   do_code_fill(off_t length);
 
+  // Return whether SYM is defined by the ABI.
+  bool
+  do_is_defined_by_abi(Symbol* sym) const
+  { return strcmp(sym->name(), "__tls_get_addr") == 0; }
+
   // Return the size of the GOT section.
   off_t
   got_size()