elf: Strip unreferenced weak undefined symbols

diff --git a/bfd/elf-bfd.h b/bfd/elf-bfd.h
index ef5dcb55e72..92a0287d40e 100644
--- a/bfd/elf-bfd.h
+++ b/bfd/elf-bfd.h
@@ -232,6 +232,8 @@  struct elf_link_hash_entry
      a strong defined symbol alias.  U.ALIAS points to a list of aliases,
      the definition having is_weakalias clear.  */
   unsigned int is_weakalias : 1;
+  /* Symbol has a relocation.  */
+  unsigned int has_reloc : 1;
 
   /* String table index in .dynstr if this is a dynamic symbol.  */
   unsigned long dynstr_index;
diff --git a/bfd/elf-vxworks.c b/bfd/elf-vxworks.c
index 4c172cd4115..36e5540f9c0 100644
--- a/bfd/elf-vxworks.c
+++ b/bfd/elf-vxworks.c
@@ -172,35 +172,39 @@  elf_vxworks_emit_relocs (bfd *output_bfd,
 	   irela += bed->s->int_rels_per_ext_rel,
 	     hash_ptr++)
 	{
-	  if (*hash_ptr
-	      && (*hash_ptr)->def_dynamic
-	      && !(*hash_ptr)->def_regular
-	      && ((*hash_ptr)->root.type == bfd_link_hash_defined
-		  || (*hash_ptr)->root.type == bfd_link_hash_defweak)
-	      && (*hash_ptr)->root.u.def.section->output_section != NULL)
+	  if (*hash_ptr)
 	    {
-	      /* This is a relocation from an executable or shared
-		 library against a symbol in a different shared
-		 library.  We are creating a definition in the output
-		 file but it does not come from any of our normal (.o)
-		 files. ie. a PLT stub.  Normally this would be a
-		 relocation against against SHN_UNDEF with the VMA of
-		 the PLT stub.  This upsets the VxWorks loader.
-		 Convert it to a section-relative relocation.  This
-		 gets some other symbols (for instance .dynbss), but
-		 is conservatively correct.  */
-	      for (j = 0; j < bed->s->int_rels_per_ext_rel; j++)
+	      (*hash_ptr)->has_reloc = 1;
+	      if ((*hash_ptr)->def_dynamic
+		  && !(*hash_ptr)->def_regular
+		  && ((*hash_ptr)->root.type == bfd_link_hash_defined
+		      || (*hash_ptr)->root.type == bfd_link_hash_defweak)
+		  && (*hash_ptr)->root.u.def.section->output_section != NULL)
 		{
-		  asection *sec = (*hash_ptr)->root.u.def.section;
-		  int this_idx = sec->output_section->target_index;
-
-		  irela[j].r_info
-		    = ELF32_R_INFO (this_idx, ELF32_R_TYPE (irela[j].r_info));
-		  irela[j].r_addend += (*hash_ptr)->root.u.def.value;
-		  irela[j].r_addend += sec->output_offset;
+		  /* This is a relocation from an executable or shared
+		     library against a symbol in a different shared
+		     library.  We are creating a definition in the output
+		     file but it does not come from any of our normal (.o)
+		     files. ie. a PLT stub.  Normally this would be a
+		     relocation against against SHN_UNDEF with the VMA of
+		     the PLT stub.  This upsets the VxWorks loader.
+		     Convert it to a section-relative relocation.  This
+		     gets some other symbols (for instance .dynbss), but
+		     is conservatively correct.  */
+		  for (j = 0; j < bed->s->int_rels_per_ext_rel; j++)
+		    {
+		      asection *sec = (*hash_ptr)->root.u.def.section;
+		      int this_idx = sec->output_section->target_index;
+
+		      irela[j].r_info
+			= ELF32_R_INFO (this_idx,
+					ELF32_R_TYPE (irela[j].r_info));
+		      irela[j].r_addend += (*hash_ptr)->root.u.def.value;
+		      irela[j].r_addend += sec->output_offset;
+		    }
+		  /* Stop the generic routine adjusting this entry.  */
+		  *hash_ptr = NULL;
 		}
-	      /* Stop the generic routine adjusting this entry.  */
-	      *hash_ptr = NULL;
 	    }
 	}
     }
diff --git a/bfd/elflink.c b/bfd/elflink.c
index 9c53bfcf7d4..4f72d1b2a90 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -2942,8 +2942,7 @@  _bfd_elf_link_output_relocs (bfd *output_bfd,
 			     asection *input_section,
 			     Elf_Internal_Shdr *input_rel_hdr,
 			     Elf_Internal_Rela *internal_relocs,
-			     struct elf_link_hash_entry **rel_hash
-			       ATTRIBUTE_UNUSED)
+			     struct elf_link_hash_entry **rel_hash)
 {
   Elf_Internal_Rela *irela;
   Elf_Internal_Rela *irelaend;
@@ -2986,9 +2985,12 @@  _bfd_elf_link_output_relocs (bfd *output_bfd,
 		      * bed->s->int_rels_per_ext_rel);
   while (irela < irelaend)
     {
+      if (*rel_hash)
+	(*rel_hash)->has_reloc = 1;
       (*swap_out) (output_bfd, irela, erel);
       irela += bed->s->int_rels_per_ext_rel;
       erel += input_rel_hdr->sh_entsize;
+      rel_hash++;
     }
 
   /* Bump the counter, so that we know where to add the next set of
@@ -10769,6 +10771,13 @@  elf_link_output_extsym (struct bfd_hash_entry *bh, void *data)
 	   && (h->root.u.undef.abfd->flags & BFD_PLUGIN) != 0)
     strip = true;
 
+  /* Remember if this symbol should be stripped.  */
+  bool should_strip = strip;
+
+  /* Strip undefined weak symbols link if they don't have relocation.  */
+  if (!strip)
+    strip = !h->has_reloc && h->root.type == bfd_link_hash_undefweak;
+
   type = h->type;
 
   /* If we're stripping it, and it's not a dynamic symbol, there's
@@ -10917,6 +10926,10 @@  elf_link_output_extsym (struct bfd_hash_entry *bh, void *data)
 	  eoinfo->failed = true;
 	  return false;
 	}
+      /* If a symbol is in the dynamic symbol table and isn't a
+	 should-strip symbol, also keep it in the symbol table.  */
+      if (!should_strip)
+	strip = false;
     }
 
   /* If we are marking the symbol as undefined, and there are no
diff --git a/ld/testsuite/ld-elf/elf.exp b/ld/testsuite/ld-elf/elf.exp
index 685b87588e7..874ba662d2b 100644
--- a/ld/testsuite/ld-elf/elf.exp
+++ b/ld/testsuite/ld-elf/elf.exp
@@ -171,6 +171,21 @@  run_ld_link_tests [list \
 	"implib" ] \
 ] \[uses_genelf\]
 
+run_ld_link_tests [list \
+    [list "Generate undefweak-1.a" \
+	"" "" \
+	$hpux \
+	{undefweak-1a.s} \
+	{} \
+	"undefweak-1.a" ] \
+    [list "Generate undefweak-1.o" \
+	"-r" "tmpdir/undefweak-1.a" \
+	$hpux \
+	{undefweak-1b.s} \
+	{{readelf {-rsW} undefweak-1.rd}} \
+	"undefweak-1.o" ] \
+] \[uses_genelf\]
+
 #v850 gas complains about .tbss.var section attributes.
 if { [check_gc_sections_available] && ![istarget "v850-*-*"] } {
     run_ld_link_tests {
diff --git a/ld/testsuite/ld-elf/undefweak-1.rd b/ld/testsuite/ld-elf/undefweak-1.rd
new file mode 100644
index 00000000000..5b48c13c892
--- /dev/null
+++ b/ld/testsuite/ld-elf/undefweak-1.rd
@@ -0,0 +1,10 @@ 
+#source: undefweak-1a.s
+#source: undefweak-1b.s
+#as:
+#ld: -r
+#readelf: -sW
+
+#failif
+#...
+.*: 0+ +0 +FUNC +WEAK +DEFAULT +UND +bar
+#pass
diff --git a/ld/testsuite/ld-elf/undefweak-1a.s b/ld/testsuite/ld-elf/undefweak-1a.s
new file mode 100644
index 00000000000..1d885fb9997
--- /dev/null
+++ b/ld/testsuite/ld-elf/undefweak-1a.s
@@ -0,0 +1,14 @@ 
+	.section .text.foobar,"axG",%progbits,foo,comdat
+	.weak foo
+	.type foo,%function
+foo:
+	.nop
+	.size foo, . - foo
+	.weak bar
+	.set bar, foo
+	.text
+	.global baz
+	.type baz,%function
+baz:
+	.dc.a foo
+	.size baz, . - baz
diff --git a/ld/testsuite/ld-elf/undefweak-1b.s b/ld/testsuite/ld-elf/undefweak-1b.s
new file mode 100644
index 00000000000..8ba34ea855e
--- /dev/null
+++ b/ld/testsuite/ld-elf/undefweak-1b.s
@@ -0,0 +1,10 @@ 
+	.section .text.foobar,"axG",%progbits,foo,comdat
+	.weak foo
+	.type foo,%function
+foo:
+	.nop
+	.size foo, . - foo
+	.text
+	.global _start
+	.set _start,foo
+	.dc.a baz
diff --git a/ld/testsuite/ld-x86-64/weakundef-1.nd b/ld/testsuite/ld-x86-64/weakundef-1.nd
new file mode 100644
index 00000000000..c4c89bfabdb
--- /dev/null
+++ b/ld/testsuite/ld-x86-64/weakundef-1.nd
@@ -0,0 +1,6 @@ 
+#nm: -n
+#target: x86_64-*-*
+
+#...
+ +w +bar
+#pass
diff --git a/ld/testsuite/ld-x86-64/weakundef-1a.s b/ld/testsuite/ld-x86-64/weakundef-1a.s
new file mode 100644
index 00000000000..b6eea3201a6
--- /dev/null
+++ b/ld/testsuite/ld-x86-64/weakundef-1a.s
@@ -0,0 +1,6 @@ 
+	.text
+	.global foo
+	.type foo,%function
+foo:
+	.nop
+	.size foo, . - foo
diff --git a/ld/testsuite/ld-x86-64/weakundef-1b.s b/ld/testsuite/ld-x86-64/weakundef-1b.s
new file mode 100644
index 00000000000..3d2da7dc548
--- /dev/null
+++ b/ld/testsuite/ld-x86-64/weakundef-1b.s
@@ -0,0 +1,8 @@ 
+	.weak bar
+	.text
+	.global _start
+	.type _start,%function
+_start:
+	mov	bar@GOTPCREL(%rip), %rax
+	mov	foo@GOTPCREL(%rip), %rax
+	.size _start, . - _start
diff --git a/ld/testsuite/ld-x86-64/x86-64.exp b/ld/testsuite/ld-x86-64/x86-64.exp
index e370f393a7a..6546fff4efc 100644
--- a/ld/testsuite/ld-x86-64/x86-64.exp
+++ b/ld/testsuite/ld-x86-64/x86-64.exp
@@ -264,6 +264,24 @@  run_ld_link_tests [list \
 	 {objdump -drj.plt tlsdesc.pd}} \
 	 "libtlsdesc.so" \
     ] \
+    [list \
+	"Generate x86-64-weakundef-1.so" \
+	"-shared -melf_x86_64" \
+	"" \
+	"--64" \
+	{weakundef-1a.s} \
+	{} \
+	"x86-64-weakundef-1.so" \
+    ] \
+    [list \
+	"Generate x86-64-weakundef-1" \
+	"-melf_x86_64" \
+	"tmpdir/x86-64-weakundef-1.so" \
+	"--64" \
+	{weakundef-1b.s} \
+	{{nm -n weakundef-1.nd}} \
+	"x86-64-weakundef-1" \
+    ] \
 ]
 
 set test_name "Mixed x86_64 and i386 input test 1"