elf: Always honor the first definition in shared object and archive

GCC doesn't put builtin function symbol references, which are defined in
the shared C library, in the IR symbol table.  When linker rescans shared
objects and archives for newly added symbol references generated from the
IR inputs, it skips definitions of the builtin functions in shared
objects and archives.

Add first_hash to elf_link_hash_table to track unreferenced definitions
defined first in shared objects and archives.  Always use them to resolve
any references.

bfd/

	PR ld/31482
	PR ld/31489
	* elf-bfd.h (elf_link_hash_table): Add first_hash.
	* elflink.c (elf_link_add_to_first_hash): New function.
	(elf_link_add_object_symbols): Initialize first_hash for an IR
	input.  Always use the first definition in shared object.  Add
	the first unreferenced dynamic definition to first_hash.
	(_bfd_elf_archive_symbol_lookup): Add the first unreferenced
	definition to first_hash..
	(elf_link_add_archive_symbols): Use the symbol definition in
	archive if symbol is defined first in this archive.
	(_bfd_elf_link_hash_table_free): Also free first_hash.

ld/

	PR ld/31482
	PR ld/31489
	* testsuite/ld-plugin/lto.exp: Add PR ld/31482 and PR ld/31489
	tests.
	* testsuite/ld-elf/pr31482a-no-lto.c: New file.
	* testsuite/ld-elf/pr31482b-no-lto.c: Likewise.
	* testsuite/ld-elf/pr31482c-no-lto.c: Likewise.
	* testsuite/ld-elf/pr31482d-no-lto.c: Likewise.
	* testsuite/ld-plugin/pass1.out: Likewise.
	* testsuite/ld-plugin/pr31482a.c: Likewise.
	* testsuite/ld-plugin/pr31482b.c: Likewise.
	* testsuite/ld-plugin/pr31482c.c: Likewise.

12 files changed, 267 insertions, 38 deletions

diff --git a/bfd/elf-bfd.h b/bfd/elf-bfd.h
index f31244f..cf043d6 100644
--- a/bfd/elf-bfd.h
+++ b/bfd/elf-bfd.h
@@ -737,6 +737,10 @@ struct elf_link_hash_table
   /* Small local sym cache.  */
   struct sym_cache sym_cache;
 
+  /* Hash table of symbols which are first defined in archives or shared
+     objects when there are any IR inputs.  */
+  struct bfd_link_hash_table *first_hash;
+
   /* Short-cuts to get to dynamic linker sections.  */
   asection *sgot;
   asection *sgotplt;
diff --git a/bfd/elflink.c b/bfd/elflink.c
index fa1f127..3db517c 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -4261,6 +4261,32 @@ _bfd_elf_link_check_relocs (bfd *abfd, struct bfd_link_info *info)
   return true;
 }
 
+/* Add the symbol NAME from ABFD to first hash.  */
+
+static void
+elf_link_add_to_first_hash (bfd *abfd, struct bfd_link_info *info,
+			    const char *name)
+{
+  struct elf_link_hash_table *htab = elf_hash_table (info);
+  /* Skip if there is no first hash.  */
+  if (htab->first_hash == NULL)
+    return;
+
+  struct bfd_link_hash_entry *e
+    = bfd_link_hash_lookup (htab->first_hash, name, true, false, true);
+  if (e == NULL)
+    info->callbacks->einfo
+      (_("%F%P: %pB: failed to add %s to first hash\n"), abfd, name);
+
+  if (e->type == bfd_link_hash_new)
+    {
+      /* Change the type to bfd_link_hash_undefined and store ABFD in
+	 u.undef->abfd.  */
+      e->type = bfd_link_hash_undefined;
+      e->u.undef.abfd = abfd;
+    }
+}
+
 /* Add symbols from an ELF object file to the linker hash table.  */
 
 static bool
@@ -4308,7 +4334,22 @@ elf_link_add_object_symbols (bfd *abfd, struct bfd_link_info *info)
     }
 
   if ((abfd->flags & DYNAMIC) == 0)
-    dynamic = false;
+    {
+      dynamic = false;
+      if ((abfd->flags & BFD_PLUGIN) != 0
+	  && is_elf_hash_table (&htab->root)
+	  && htab->first_hash == NULL)
+	{
+	  /* Initialize first_hash for an IR input.  */
+	  htab->first_hash = (struct bfd_link_hash_table *)
+	    xmalloc (sizeof (struct bfd_link_hash_table));
+	  if (!bfd_hash_table_init (&htab->first_hash->table,
+				    _bfd_link_hash_newfunc,
+				    sizeof (struct bfd_link_hash_entry)))
+	    info->callbacks->einfo
+	      (_("%F%P: first_hash failed to initialize: %E\n"));
+	}
+    }
   else
     {
       dynamic = true;
@@ -5161,16 +5202,31 @@ elf_link_add_object_symbols (bfd *abfd, struct bfd_link_info *info)
 	  if (skip)
 	    continue;
 
-	  /* Override a definition only if the new symbol matches the
-	     existing one.  */
-	  if (override && matched)
-	    definition = false;
-
 	  h = *sym_hash;
 	  while (h->root.type == bfd_link_hash_indirect
 		 || h->root.type == bfd_link_hash_warning)
 	    h = (struct elf_link_hash_entry *) h->root.u.i.link;
 
+	  /* Override a definition only if the new symbol matches the
+	     existing one.  */
+	  if (override && matched)
+	    {
+	      definition = false;
+	      if (htab->first_hash != NULL
+		  && (elf_dyn_lib_class (abfd) & DYN_AS_NEEDED) != 0
+		  && h->root.non_ir_ref_regular)
+		{
+		  /* When reloading --as-needed shared objects for new
+		     symbols added from IR inputs, if this shared object
+		     has the first definition, use it.  */
+		  struct bfd_link_hash_entry *e
+		    = bfd_link_hash_lookup (htab->first_hash, name,
+					    false, false, true);
+		  if (e != NULL && e->u.undef.abfd == abfd)
+		    definition = true;
+		}
+	    }
+
 	  if (h->versioned != unversioned
 	      && elf_tdata (abfd)->verdef != NULL
 	      && vernum > 1
@@ -5520,8 +5576,9 @@ elf_link_add_object_symbols (bfd *abfd, struct bfd_link_info *info)
 	  if (!add_needed
 	      && matched
 	      && definition
-	      && h->root.type != bfd_link_hash_indirect
-	      && ((dynsym
+	      && h->root.type != bfd_link_hash_indirect)
+	    {
+	      if ((dynsym
 		   && h->ref_regular_nonweak)
 		  || (old_bfd != NULL
 		      && (old_bfd->flags & BFD_PLUGIN) != 0
@@ -5530,37 +5587,43 @@ elf_link_add_object_symbols (bfd *abfd, struct bfd_link_info *info)
 		  || (h->ref_dynamic_nonweak
 		      && (elf_dyn_lib_class (abfd) & DYN_AS_NEEDED) != 0
 		      && !on_needed_list (elf_dt_name (abfd),
-					  htab->needed, NULL))))
-	    {
-	      const char *soname = elf_dt_name (abfd);
-
-	      info->callbacks->minfo ("%!", soname, old_bfd,
-				      h->root.root.string);
-
-	      /* A symbol from a library loaded via DT_NEEDED of some
-		 other library is referenced by a regular object.
-		 Add a DT_NEEDED entry for it.  Issue an error if
-		 --no-add-needed is used and the reference was not
-		 a weak one.  */
-	      if (old_bfd != NULL
-		  && (elf_dyn_lib_class (abfd) & DYN_NO_NEEDED) != 0)
+					  htab->needed, NULL)))
 		{
-		  _bfd_error_handler
-		    /* xgettext:c-format */
-		    (_("%pB: undefined reference to symbol '%s'"),
-		     old_bfd, name);
-		  bfd_set_error (bfd_error_missing_dso);
-		  goto error_free_vers;
-		}
+		  const char *soname = elf_dt_name (abfd);
+
+		  info->callbacks->minfo ("%!", soname, old_bfd,
+					  h->root.root.string);
+
+		  /* A symbol from a library loaded via DT_NEEDED of some
+		     other library is referenced by a regular object.
+		     Add a DT_NEEDED entry for it.  Issue an error if
+		     --no-add-needed is used and the reference was not
+		     a weak one.  */
+		  if (old_bfd != NULL
+		      && (elf_dyn_lib_class (abfd) & DYN_NO_NEEDED) != 0)
+		    {
+		      _bfd_error_handler
+			/* xgettext:c-format */
+			(_("%pB: undefined reference to symbol '%s'"),
+			 old_bfd, name);
+		      bfd_set_error (bfd_error_missing_dso);
+		      goto error_free_vers;
+		    }
 
-	      elf_dyn_lib_class (abfd) = (enum dynamic_lib_link_class)
-		(elf_dyn_lib_class (abfd) & ~DYN_AS_NEEDED);
+		  elf_dyn_lib_class (abfd) = (enum dynamic_lib_link_class)
+		    (elf_dyn_lib_class (abfd) & ~DYN_AS_NEEDED);
 
-	      /* Create dynamic sections for backends that require
-		 that be done before setup_gnu_properties.  */
-	      if (!_bfd_elf_link_create_dynamic_sections (abfd, info))
-		return false;
-	      add_needed = true;
+		  /* Create dynamic sections for backends that require
+		     that be done before setup_gnu_properties.  */
+		  if (!_bfd_elf_link_create_dynamic_sections (abfd, info))
+		    return false;
+		  add_needed = true;
+		}
+	      else if (dynamic
+		       && h->root.u.def.section->owner == abfd)
+		/* Add this symbol to first hash if this shared
+		   object has the first definition.  */
+		elf_link_add_to_first_hash (abfd, info, name);
 	    }
 	}
     }
@@ -6005,7 +6068,12 @@ _bfd_elf_archive_symbol_lookup (bfd *abfd,
 
   p = strchr (name, ELF_VER_CHR);
   if (p == NULL || p[1] != ELF_VER_CHR)
-    return h;
+    {
+      /* Add this symbol to first hash if this archive has the first
+	 definition.  */
+      elf_link_add_to_first_hash (abfd, info, name);
+      return h;
+    }
 
   /* First check with only one `@'.  */
   len = strlen (name);
@@ -6144,7 +6212,22 @@ elf_link_add_archive_symbols (bfd *abfd, struct bfd_link_info *info)
 	      if (h->type != bfd_link_hash_undefweak)
 		/* Symbol must be defined.  Don't check it again.  */
 		included[i] = true;
-	      continue;
+
+	      /* Ignore the archive if the symbol isn't defined in a
+		 shared object.  */
+	      if (!((struct elf_link_hash_entry *) h)->def_dynamic)
+		continue;
+	      /* Ignore the dynamic definition if symbol is first
+		 defined in this archive.  */
+	      struct elf_link_hash_table *htab = elf_hash_table (info);
+	      if (htab->first_hash == NULL)
+		continue;
+	      struct bfd_link_hash_entry *e
+		= bfd_link_hash_lookup (htab->first_hash,
+					symdef->name, false, false,
+					true);
+	      if (e == NULL || e->u.undef.abfd != abfd)
+		continue;
 	    }
 
 	  /* We need to include this archive member.  */
@@ -8226,6 +8309,11 @@ _bfd_elf_link_hash_table_free (bfd *obfd)
     _bfd_elf_strtab_free (htab->dynstr);
   _bfd_merge_sections_free (htab->merge_info);
   _bfd_generic_link_hash_table_free (obfd);
+  if (htab->first_hash != NULL)
+    {
+      bfd_hash_table_free (&htab->first_hash->table);
+      free (htab->first_hash);
+    }
 }
 
 /* This is a hook for the ELF emulation code in the generic linker to
diff --git a/ld/testsuite/ld-elf/pr31482a-no-lto.c b/ld/testsuite/ld-elf/pr31482a-no-lto.c
new file mode 100644
index 0000000..abc23be
--- /dev/null
+++ b/ld/testsuite/ld-elf/pr31482a-no-lto.c
@@ -0,0 +1,8 @@
+extern void foo (void);
+
+int
+main()
+{
+  foo ();
+  return 0;
+}
diff --git a/ld/testsuite/ld-elf/pr31482b-no-lto.c b/ld/testsuite/ld-elf/pr31482b-no-lto.c
new file mode 100644
index 0000000..f88254d
--- /dev/null
+++ b/ld/testsuite/ld-elf/pr31482b-no-lto.c
@@ -0,0 +1,10 @@
+void
+func (void)
+{
+}
+
+void
+bar (void)
+{
+  func ();
+}
diff --git a/ld/testsuite/ld-elf/pr31482c-no-lto.c b/ld/testsuite/ld-elf/pr31482c-no-lto.c
new file mode 100644
index 0000000..bf326dd
--- /dev/null
+++ b/ld/testsuite/ld-elf/pr31482c-no-lto.c
@@ -0,0 +1,15 @@
+#include <stdlib.h>
+#include <stdio.h>
+
+void
+abort (void)
+{
+  printf ("PASS\n");
+  exit (0);
+}
+
+void
+foo (void)
+{
+  abort ();
+}
diff --git a/ld/testsuite/ld-elf/pr31482d-no-lto.c b/ld/testsuite/ld-elf/pr31482d-no-lto.c
new file mode 100644
index 0000000..7cdaff0
--- /dev/null
+++ b/ld/testsuite/ld-elf/pr31482d-no-lto.c
@@ -0,0 +1,9 @@
+void
+func (void)
+{
+}
+
+void
+foo (void)
+{
+}
diff --git a/ld/testsuite/ld-elf/shared.exp b/ld/testsuite/ld-elf/shared.exp
index 277dc7b..9e89077 100644
--- a/ld/testsuite/ld-elf/shared.exp
+++ b/ld/testsuite/ld-elf/shared.exp
@@ -912,6 +912,30 @@ run_cc_link_tests [list \
 	{{readelf {--dyn-syms --wide} pr28348.rd}} \
 	"pr28348" \
     ] \
+    [list \
+	"Build pr31482b-no-lto.so" \
+	"-shared" \
+	"-fPIC" \
+	{pr31482b-no-lto.c} \
+	{} \
+	"pr31482b-no-lto.so" \
+    ] \
+    [list \
+	"Build pr31482c-no-lto.a" \
+	"" \
+	"" \
+	{pr31482c-no-lto.c} \
+	{} \
+	"pr31482c-no-lto.a" \
+    ] \
+    [list \
+	"Build pr31482d-no-lto.a" \
+	"" \
+	"" \
+	{pr31482d-no-lto.c} \
+	{} \
+	"pr31482d-no-lto.a" \
+    ] \
 ]
 
 # pr19073.s uses .set, which has a different meaning on alpha.
@@ -1165,6 +1189,18 @@ set run_tests [list \
      "" "" \
      {pr26590c.c pr26590d.c} "pr26590" "pass.out" "" "c" "" \
      "-Wl,--as-needed tmpdir/libpr26590a.so tmpdir/libpr26590b.so" ] \
+    [list "Run pr31482 (no-lto)" \
+     "-Wl,--no-as-needed" \
+     "" \
+     {pr31482a-no-lto.c} \
+     "pr31482-no-lto" \
+     "pass.out" \
+     "" \
+     "c" \
+     "" \
+     "tmpdir/pr31482b-no-lto.so tmpdir/pr31482c-no-lto.a \
+      tmpdir/pr31482d-no-lto.a" \
+    ] \
 ]
 
 # NetBSD ELF systems do not currently support the .*_array sections.
diff --git a/ld/testsuite/ld-plugin/lto.exp b/ld/testsuite/ld-plugin/lto.exp
index 259a064..b56d71a 100644
--- a/ld/testsuite/ld-plugin/lto.exp
+++ b/ld/testsuite/ld-plugin/lto.exp
@@ -539,6 +539,22 @@ set lto_link_elf_tests [list \
    "" \
    "pr30281.so" \
   ] \
+  [list \
+   "Build pr31482b.a" \
+   "" \
+   "" \
+   {pr31482b.c} \
+   "" \
+   "pr31482b.a" \
+  ] \
+  [list \
+   "Build pr31482c.so" \
+   "-shared" \
+   "-fPIC" \
+   {pr31482c.c} \
+   "" \
+   "pr31482c.so" \
+  ] \
 ]
 
 # PR 14918 checks that libgcc is not spuriously included in a shared link of
@@ -722,6 +738,22 @@ set lto_run_elf_shared_tests [list \
    {-Wl,--as-needed,-R,tmpdir} {} \
    {lto-19c.c} {lto-19.exe} {pass.out} {-flto -O2} {c} {} \
    {tmpdir/liblto-19.so tmpdir/liblto-19.a}] \
+  [list {pr31482a} \
+   {-Wl,--no-as-needed,-R,tmpdir} {} \
+   {pr31482a.c} {pr31482a.exe} {pass.out} {-flto} {c} {} \
+   {tmpdir/pr31482b.a tmpdir/pr31482c.so}] \
+  [list {pr31482b} \
+   {-Wl,--no-as-needed,-R,tmpdir} {} \
+   {pr31482a.c} {pr31482b.exe} {pass1.out} {-flto} {c} {} \
+   {tmpdir/pr31482c.so tmpdir/pr31482b.a}] \
+  [list {pr31489a} \
+   {-Wl,--as-needed,-R,tmpdir} {} \
+   {pr31482a.c} {pr31489a.exe} {pass.out} {-flto} {c} {} \
+   {tmpdir/pr31482b.a tmpdir/pr31482c.so}] \
+  [list {pr31489b} \
+   {-Wl,--as-needed,-R,tmpdir} {} \
+   {pr31482a.c} {pr31489b.exe} {pass1.out} {-flto} {c} {} \
+   {tmpdir/pr31482c.so tmpdir/pr31482b.a}] \
 ]
 
 # LTO run-time tests for ELF
diff --git a/ld/testsuite/ld-plugin/pass1.out b/ld/testsuite/ld-plugin/pass1.out
new file mode 100644
index 0000000..8e5c818
--- /dev/null
+++ b/ld/testsuite/ld-plugin/pass1.out
@@ -0,0 +1 @@
+PASS1
diff --git a/ld/testsuite/ld-plugin/pr31482a.c b/ld/testsuite/ld-plugin/pr31482a.c
new file mode 100644
index 0000000..0693e47
--- /dev/null
+++ b/ld/testsuite/ld-plugin/pr31482a.c
@@ -0,0 +1,8 @@
+#include <stdlib.h>
+
+int
+main()
+{
+  abort ();
+  return 0;
+}
diff --git a/ld/testsuite/ld-plugin/pr31482b.c b/ld/testsuite/ld-plugin/pr31482b.c
new file mode 100644
index 0000000..3c24173
--- /dev/null
+++ b/ld/testsuite/ld-plugin/pr31482b.c
@@ -0,0 +1,9 @@
+#include <stdlib.h>
+#include <stdio.h>
+
+void
+abort (void)
+{
+  printf ("PASS\n");
+  exit (0);
+}
diff --git a/ld/testsuite/ld-plugin/pr31482c.c b/ld/testsuite/ld-plugin/pr31482c.c
new file mode 100644
index 0000000..5c3b509
--- /dev/null
+++ b/ld/testsuite/ld-plugin/pr31482c.c
@@ -0,0 +1,9 @@
+#include <stdlib.h>
+#include <stdio.h>
+
+void
+abort (void)
+{
+  printf ("PASS1\n");
+  exit (0);
+}