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Re: gold cannot handle _start in a library


Roland McGrath <mcgrathr@google.com> writes:

> Given:
>
> 	$ gcc -c -xc <(echo '_start(){}') -o start.o
> 	$ ar cq libstart.a start.o
> 	$ ./gold/ld-new -o foo libstart.a
>
> The output file foo is an empty ELF file.
> With:
>
> 	$ ./gold/ld-new -o foo -e _start libstart.a
> 	./gold/ld-new: warning: cannot find entry symbol '_start'
>
> The results are the same, plus the extra warning.
>
> BFD ld does not have this bug.
> I tested with today's trunk builds of gold and BFD ld.

Thanks.  Fixed like so.  Committed to mainline.

Ian


2011-05-24  Ian Lance Taylor  <iant@google.com>

	* archive.cc (Library_base::should_include_member): Pull in object
	from archive if it defines the entry symbol.
	* parameters.cc (Parameters::entry): New function.
	* parameters.h (class Parameters): Declare entry.
	* output.h (class Output_file_header): Remove entry_ field.
	* output.cc (Output_file_header::Output_file_header): Remove entry
	parameter.  Change all callers.
	(Output_file_header::entry): Use parameters->entry.
	* gold.cc (queue_middle_tasks): Likewise.
	* plugin.cc (Plugin_hook::run): Likewise.


Index: archive.cc
===================================================================
RCS file: /cvs/src/src/gold/archive.cc,v
retrieving revision 1.67
diff -p -u -r1.67 archive.cc
--- archive.cc	12 Apr 2011 00:44:47 -0000	1.67
+++ archive.cc	25 May 2011 00:11:15 -0000
@@ -113,6 +113,11 @@ Library_base::should_include_member(Symb
 	  *why = buf;
 	  delete[] buf;
 	}
+      else if (strcmp(sym_name, parameters->entry()) == 0)
+	{
+	  *why = "entry symbol ";
+	  *why += sym_name;
+	}
       else
 	return Library_base::SHOULD_INCLUDE_UNKNOWN;
     }
Index: gold.cc
===================================================================
RCS file: /cvs/src/src/gold/gold.cc,v
retrieving revision 1.89
diff -p -u -r1.89 gold.cc
--- gold.cc	24 May 2011 23:31:06 -0000	1.89
+++ gold.cc	25 May 2011 00:11:15 -0000
@@ -501,11 +501,7 @@ queue_middle_tasks(const General_options
   if (parameters->options().gc_sections())
     {
       // Find the start symbol if any.
-      Symbol* start_sym;
-      if (parameters->options().entry())
-        start_sym = symtab->lookup(parameters->options().entry());
-      else
-        start_sym = symtab->lookup("_start");
+      Symbol* start_sym = symtab->lookup(parameters->entry());
       if (start_sym != NULL)
         {
           bool is_ordinary;
Index: layout.cc
===================================================================
RCS file: /cvs/src/src/gold/layout.cc,v
retrieving revision 1.196
diff -p -u -r1.196 layout.cc
--- layout.cc	24 May 2011 21:57:28 -0000	1.196
+++ layout.cc	25 May 2011 00:11:17 -0000
@@ -2192,9 +2192,8 @@ Layout::finalize(const Input_objects* in
      : new Output_segment_headers(this->segment_list_));
 
   // Lay out the file header.
-  Output_file_header* file_header
-    = new Output_file_header(target, symtab, segment_headers,
-			     parameters->options().entry());
+  Output_file_header* file_header = new Output_file_header(target, symtab,
+							   segment_headers);
 
   this->special_output_list_.push_back(file_header);
   if (segment_headers != NULL)
Index: output.h
===================================================================
RCS file: /cvs/src/src/gold/output.h,v
retrieving revision 1.123
diff -p -u -r1.123 output.h
--- output.h	24 May 2011 23:31:07 -0000	1.123
+++ output.h	25 May 2011 00:11:19 -0000
@@ -566,8 +566,7 @@ class Output_file_header : public Output
  public:
   Output_file_header(const Target*,
 		     const Symbol_table*,
-		     const Output_segment_headers*,
-		     const char* entry);
+		     const Output_segment_headers*);
 
   // Add information about the section headers.  We lay out the ELF
   // file header before we create the section headers.
@@ -614,7 +613,6 @@ class Output_file_header : public Output
   const Output_segment_headers* segment_header_;
   const Output_section_headers* section_header_;
   const Output_section* shstrtab_;
-  const char* entry_;
 };
 
 // Output sections are mainly comprised of input sections.  However,
Index: output.cc
===================================================================
RCS file: /cvs/src/src/gold/output.cc,v
retrieving revision 1.146
diff -p -u -r1.146 output.cc
--- output.cc	24 May 2011 23:31:07 -0000	1.146
+++ output.cc	25 May 2011 00:11:21 -0000
@@ -425,14 +425,12 @@ Output_segment_headers::do_size() const
 
 Output_file_header::Output_file_header(const Target* target,
 				       const Symbol_table* symtab,
-				       const Output_segment_headers* osh,
-				       const char* entry)
+				       const Output_segment_headers* osh)
   : target_(target),
     symtab_(symtab),
     segment_header_(osh),
     section_header_(NULL),
-    shstrtab_(NULL),
-    entry_(entry)
+    shstrtab_(NULL)
 {
   this->set_data_size(this->do_size());
 }
@@ -572,22 +570,16 @@ Output_file_header::do_sized_write(Outpu
   of->write_output_view(0, ehdr_size, view);
 }
 
-// Return the value to use for the entry address.  THIS->ENTRY_ is the
-// symbol specified on the command line, if any.
+// Return the value to use for the entry address.
 
 template<int size>
 typename elfcpp::Elf_types<size>::Elf_Addr
 Output_file_header::entry()
 {
-  const bool should_issue_warning = (this->entry_ != NULL
+  const bool should_issue_warning = (parameters->options().entry() != NULL
 				     && !parameters->options().relocatable()
                                      && !parameters->options().shared());
-
-  // FIXME: Need to support target specific entry symbol.
-  const char* entry = this->entry_;
-  if (entry == NULL)
-    entry = "_start";
-
+  const char* entry = parameters->entry();
   Symbol* sym = this->symtab_->lookup(entry);
 
   typename Sized_symbol<size>::Value_type v;
Index: parameters.cc
===================================================================
RCS file: /cvs/src/src/gold/parameters.cc,v
retrieving revision 1.34
diff -p -u -r1.34 parameters.cc
--- parameters.cc	14 Oct 2010 22:10:22 -0000	1.34
+++ parameters.cc	25 May 2011 00:11:21 -0000
@@ -211,6 +211,20 @@ Parameters::check_target_endianness()
     }
 }
 
+// Return the name of the entry symbol.
+
+const char*
+Parameters::entry() const
+{
+  const char* ret = this->options().entry();
+  if (ret == NULL)
+    {
+      // FIXME: Need to support target specific entry symbol.
+      ret = "_start";
+    }
+  return ret;
+}
+
 // Set the incremental linking mode to INCREMENTAL_FULL.  Used when
 // the linker determines that an incremental update is not possible.
 // Returns false if the incremental mode was INCREMENTAL_UPDATE,
Index: parameters.h
===================================================================
RCS file: /cvs/src/src/gold/parameters.h,v
retrieving revision 1.30
diff -p -u -r1.30 parameters.h
--- parameters.h	14 Oct 2010 22:10:22 -0000	1.30
+++ parameters.h	25 May 2011 00:11:21 -0000
@@ -134,6 +134,10 @@ class Parameters
     return debug_;
   }
 
+  // Return the name of the entry symbol.
+  const char*
+  entry() const;
+
   // A convenience routine for combining size and endianness.  It also
   // checks the HAVE_TARGET_FOO configure options and dies if the
   // current target's size/endianness is not supported according to
Index: plugin.cc
===================================================================
RCS file: /cvs/src/src/gold/plugin.cc,v
retrieving revision 1.46
diff -p -u -r1.46 plugin.cc
--- plugin.cc	12 Apr 2011 00:44:48 -0000	1.46
+++ plugin.cc	25 May 2011 00:11:21 -0000
@@ -1218,11 +1218,7 @@ void
 Plugin_hook::run(Workqueue* workqueue)
 {
   gold_assert(this->options_.has_plugins());
-  Symbol* start_sym;
-  if (parameters->options().entry())
-    start_sym = this->symtab_->lookup(parameters->options().entry());
-  else
-    start_sym = this->symtab_->lookup("_start");
+  Symbol* start_sym = this->symtab_->lookup(parameters->entry());
   if (start_sym != NULL)
     start_sym->set_in_real_elf();
 

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