[BFD][PR21703]Override the new defined symbol with the old normal symbol when --allow-multiple-definition is provided.

The behavior of _bfd_elf_merge_symbol and _bfd_generic_link_add_one_symbol is
inconsistent.

In multiple definition case, _bfd_elf_merge_symbol decided to override the old
symbol definition with the new defintion, (size, type, target data)
In _bfd_generic_link_add_one_symbol, it simply return without doing anything
because of allow-multiple-definition is provided.
This leaves the symbol in a wrong state.

Here, following the documentation, I made this patch to force the old definition
override the new definition if the old symbol is not dynamic or weak.
Because, in those two cases, it's expected to do some merge. I have checked
that, those two cases are properly handled.

bfd/
	PR ld/21703
	* elflink.c (_bfd_elf_merge_symbol): Handle multiple definition case.

ld/

	PR ld/21703
	* testsuite/ld-elf/elf.exp: Run new tests.
	* testsuite/ld-elf/pr21703-1.s: New.
	* testsuite/ld-elf/pr21703-2.s: New.
	* testsuite/ld-elf/pr21703-3.s: New.
	* testsuite/ld-elf/pr21703-4.s: New.
	* testsuite/ld-elf/pr21703-r.sd: New.
	* testsuite/ld-elf/pr21703-shared.sd: New.
	* testsuite/ld-elf/pr21703.sd: New.
	* testsuite/ld-elf/pr21703.ver: New.

bfd/ChangeLog

@@ -1,3 +1,8 @@
+2017-10-24  Renlin Li  <renlin.li@arm.com>
+
+	PR ld/21703
+	* elflink.c (_bfd_elf_merge_symbol): Handle multiple definition case.
+
 2017-10-23  Nick Clifton  <nickc@redhat.com>
 
 	PR 22319

bfd/elflink.c

@@ -1036,6 +1036,7 @@ _bfd_elf_merge_symbol (bfd *abfd,
   bfd_boolean newweak, oldweak, newfunc, oldfunc;
   const struct elf_backend_data *bed;
   char *new_version;
+  bfd_boolean default_sym = *matched;
 
   *skip = FALSE;
   *override = FALSE;
@@ -1557,6 +1558,18 @@ _bfd_elf_merge_symbol (bfd *abfd,
       sec = *psec;
     }
 
+  /* There are multiple definitions of a normal symbol.
+     Skip the default symbol as well.  */
+  if (olddef && !olddyn && !oldweak && newdef && !newdyn && !newweak
+      && !default_sym && h->def_regular)
+    {
+      /* Handle a multiple definition.  */
+      (*info->callbacks->multiple_definition) (info, &h->root,
+					       abfd, sec, *pvalue);
+      *skip = TRUE;
+      return TRUE;
+    }
+
   /* If both the old and the new symbols look like common symbols in a
      dynamic object, set the size of the symbol to the larger of the
      two.  */

ld/ChangeLog

@@ -1,3 +1,16 @@
+2017-10-24  Renlin Li  <renlin.li@arm.com>
+
+	PR ld/21703
+	* testsuite/ld-elf/elf.exp: Run new tests.
+	* testsuite/ld-elf/pr21703-1.s: New.
+	* testsuite/ld-elf/pr21703-2.s: New.
+	* testsuite/ld-elf/pr21703-3.s: New.
+	* testsuite/ld-elf/pr21703-4.s: New.
+	* testsuite/ld-elf/pr21703-r.sd: New.
+	* testsuite/ld-elf/pr21703-shared.sd: New.
+	* testsuite/ld-elf/pr21703.sd: New.
+	* testsuite/ld-elf/pr21703.ver: New.
+
 2017-10-23  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* configure.tgt (i[3-7]86-*-linux-*): Move elf32_x86_64 from

ld/testsuite/ld-elf/elf.exp

@@ -70,6 +70,18 @@ run_ld_link_tests [list \
 	{symbol3w.s} {} "symbol3w.a" ] \
 ]
 
+run_ld_link_tests [list \
+    [list "PR ld/21703" \
+	"--allow-multiple-definition tmpdir/pr21703-1.o tmpdir/pr21703-2.o" "" "" \
+	{pr21703-1.s pr21703-2.s} {{readelf {-s} pr21703.sd}} "pr21703" ] \
+    [list "PR ld/21703 -r" \
+	"-r --allow-multiple-definition tmpdir/pr21703-3.o tmpdir/pr21703-4.o" "" "" \
+	{pr21703-3.s pr21703-4.s} {{readelf {-s} pr21703-r.sd}} "pr21703.o" ] \
+    [list "PR ld/21703 shared" \
+	"-shared --allow-multiple-definition --version-script pr21703.ver tmpdir/pr21703-3.o tmpdir/pr21703-4.o" "" "" \
+	{pr21703-3.s pr21703-4.s} {{readelf {--dyn-syms} pr21703-shared.sd}} "pr21703.so" ] \
+]
+
 if { [check_shared_lib_support] } then {
     run_ld_link_tests {
 	{"Build pr14170a.o" "" "" "" {pr14170a.s} {} "pr14170.a" }

ld/testsuite/ld-elf/pr21703-1.s

@@ -0,0 +1,6 @@
+	.text
+	.globl	foo
+	.type	foo, %function
+foo:
+	.space	4
+	.size	foo, 4

ld/testsuite/ld-elf/pr21703-2.s

@@ -0,0 +1,6 @@
+	.text
+	.globl	foo
+	.type	foo, %function
+foo:
+	.space	16
+	.size	foo, 16

ld/testsuite/ld-elf/pr21703-3.s

@@ -0,0 +1,15 @@
+	.text
+	.global foo
+	.type	foo, %function
+foo:
+	.space	4
+	.size	foo, 4
+
+	.global foo1
+	.type	foo1, %function
+foo1:
+	.space	32
+	.size	foo1, 32
+
+	.symver	foo, foo@FOO
+	.symver	foo1, foo@@FOO1

ld/testsuite/ld-elf/pr21703-4.s

@@ -0,0 +1,15 @@
+	.text
+	.global bar
+	.type	bar, %function
+bar:
+	.space	16
+	.size	bar, 16
+
+	.global bar1
+	.type	bar1, %function
+bar1:
+	.space	8
+	.size	bar1, 8
+
+	.symver	bar, foo@FOO
+	.symver	bar1, foo@@FOO1

ld/testsuite/ld-elf/pr21703-r.sd

@@ -0,0 +1,9 @@
+Symbol table '.symtab' contains .* entries:
+#...
+.*: [0-9a-fA-F]* +4 +FUNC +GLOBAL +DEFAULT +. foo@FOO
+.*: [0-9a-fA-F]* +32 +FUNC +GLOBAL +DEFAULT +. foo1
+.*: [0-9a-fA-F]* +32 +FUNC +GLOBAL +DEFAULT +. foo@@FOO1
+.*: [0-9a-fA-F]* +8 +FUNC +GLOBAL +DEFAULT +. bar1
+.*: [0-9a-fA-F]* +4 +FUNC +GLOBAL +DEFAULT +. foo
+.*: [0-9a-fA-F]* +16 +FUNC +GLOBAL +DEFAULT +. bar
+#pass

ld/testsuite/ld-elf/pr21703-shared.sd

@@ -0,0 +1,8 @@
+Symbol table '\.dynsym' contains [0-9]+ entries:
+ +Num: +Value +Size Type +Bind +Vis +Ndx Name
+#...
+ +[0-9]+: +[0-9a-f]+ +4 +FUNC +GLOBAL +DEFAULT +[0-9] +foo@FOO
+ +[0-9]+: +[0-9a-f]+ +0 +OBJECT +GLOBAL +DEFAULT +ABS +FOO1
+ +[0-9]+: +[0-9a-f]+ +32 +FUNC +GLOBAL +DEFAULT +[0-9] +foo@@FOO1
+ +[0-9]+: +[0-9a-f]+ +0 +OBJECT +GLOBAL +DEFAULT +ABS +FOO
+#...

ld/testsuite/ld-elf/pr21703.sd

@@ -0,0 +1,4 @@
+Symbol table '.symtab' contains .* entries:
+#...
+.*: [0-9a-fA-F]* +4 +FUNC +GLOBAL +DEFAULT +. foo
+#pass

ld/testsuite/ld-elf/pr21703.ver

@@ -0,0 +1,4 @@
+FOO
+{ global: foo; local: *; };
+FOO1
+{ global: foo; local: *; };