[binutils-gdb] Add option --weak-unresolved-symbols to treat unresolved as weak references.

[Sriraman Tallam <tmsriram at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=65eb8c79be0c71f9b52d14563c0817fc5ca33c0d

commit 65eb8c79be0c71f9b52d14563c0817fc5ca33c0d
Author: Sriraman Tallam <tmsriram@google.com>
Date:   Thu Apr 23 13:48:24 2015 -0700

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

Diff:
---
 gold/testsuite/weak_unresolved_symbols_test.cc | 45 ++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/gold/testsuite/weak_unresolved_symbols_test.cc b/gold/testsuite/weak_unresolved_symbols_test.cc
new file mode 100644
index 0000000..ec2c462
--- /dev/null
+++ b/gold/testsuite/weak_unresolved_symbols_test.cc
@@ -0,0 +1,45 @@
+// weak_unresolved_symbols_test.cc -- a test case for gold
+
+// Copyright (C) 2015 Free Software Foundation, Inc.
+// Written by Sriraman Tallam <tmsriram@google.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.
+
+// Test --weak-unresolved-symbols.  Symbol foo remains unresolved but
+// with -fPIE, needs a GOT entry and has a dynsym entry and a dynamic
+// relocation against it created.  This  will fail to link and run without
+// --weak-unresolved-symbols.  With --warn-unresolved-symbols, it will link
+// but the dynamic linker will complain that foo(_Z3foov) is unresolved.
+
+extern int foo();
+
+int bar() {
+  return 0;
+}
+
+int (*p)() = &bar;
+
+int main() {
+  if (p == &foo)
+    {
+      foo();
+    }
+  else
+    (*p)();
+  return 0;
+}