ld: Properly override the IR definition

We change the previous definition in the IR object to undefweak only
after all LTO symbols have been read.

include/

	PR ld/26262
	PR ld/26267
	* bfdlink.h (bfd_link_info): Add lto_all_symbols_read.

ld/

	PR ld/26262
	PR ld/26267
	* ldlang.c (lang_process): Set lto_all_symbols_read after all
	LTO IR symbols have been read.
	* plugin.c (plugin_notice): Override the IR definition only if
	all LTO IR symbols have been read or the new definition is
	non-weak and the the IR definition is weak
	* testsuite/ld-plugin/lto.exp: Run PR ld/26262 and ld/26267
	tests.
	* testsuite/ld-plugin/pr26262a.c: New file.
	* testsuite/ld-plugin/pr26262b.c: Likewise.
	* testsuite/ld-plugin/pr26262c.c: Likewise.
	* testsuite/ld-plugin/pr26267.err: Likewise.
	* testsuite/ld-plugin/pr26267a.c: Likewise.
	* testsuite/ld-plugin/pr26267b.c: Likewise.
	* testsuite/ld-plugin/pr26267c.c: Likewise.

(cherry picked from commit 0e6a3f07f50723d1831291492b96fdf74bcbdc11)

include/ChangeLog

@@ -1,3 +1,9 @@
+2020-07-22  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR ld/26262
+	PR ld/26267
+	* bfdlink.h (bfd_link_info): Add lto_all_symbols_read.
+
 2020-07-04  Nick Clifton  <nickc@redhat.com>
 
 	Binutils 2.35 branch created.

include/bfdlink.h

@@ -361,6 +361,9 @@ struct bfd_link_info
   /* TRUE if the LTO plugin is active.  */
   unsigned int lto_plugin_active: 1;
 
+  /* TRUE if all LTO IR symbols have been read.  */
+  unsigned int lto_all_symbols_read : 1;
+
   /* TRUE if global symbols in discarded sections should be stripped.  */
   unsigned int strip_discarded: 1;
 

ld/ChangeLog

@@ -1,3 +1,22 @@
+2020-07-22  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR ld/26262
+	PR ld/26267
+	* ldlang.c (lang_process): Set lto_all_symbols_read after all
+	LTO IR symbols have been read.
+	* plugin.c (plugin_notice): Override the IR definition only if
+	all LTO IR symbols have been read or the new definition is
+	non-weak and the the IR definition is weak
+	* testsuite/ld-plugin/lto.exp: Run PR ld/26262 and ld/26267
+	tests.
+	* testsuite/ld-plugin/pr26262a.c: New file.
+	* testsuite/ld-plugin/pr26262b.c: Likewise.
+	* testsuite/ld-plugin/pr26262c.c: Likewise.
+	* testsuite/ld-plugin/pr26267.err: Likewise.
+	* testsuite/ld-plugin/pr26267a.c: Likewise.
+	* testsuite/ld-plugin/pr26267b.c: Likewise.
+	* testsuite/ld-plugin/pr26267c.c: Likewise.
+
 2020-07-20  Nick Clifton  <nickc@redhat.com>
 
 	* testsuite/ld-powerpc/powerpc.exp (ppcelftests): Use section name

ld/ldlang.c

@@ -7874,6 +7874,7 @@ lang_process (void)
       if (plugin_call_all_symbols_read ())
 	einfo (_("%F%P: %s: plugin reported error after all symbols read\n"),
 	       plugin_error_plugin ());
+      link_info.lto_all_symbols_read = TRUE;
       /* Open any newly added files, updating the file chains.  */
       plugin_undefs = link_info.hash->undefs_tail;
       open_input_bfds (*added.tail, OPEN_BFD_NORMAL);

ld/plugin.c

@@ -1433,12 +1433,16 @@ plugin_notice (struct bfd_link_info *info,
 	 new value from a real BFD.  Weak symbols are not normally
 	 overridden by a new weak definition, and strong symbols
 	 will normally cause multiple definition errors.  Avoid
-	 this by making the symbol appear to be undefined.  */
-      else if (((h->type == bfd_link_hash_defweak
-		 || h->type == bfd_link_hash_defined)
-		&& is_ir_dummy_bfd (sym_bfd = h->u.def.section->owner))
-	       || (h->type == bfd_link_hash_common
-		   && is_ir_dummy_bfd (sym_bfd = h->u.c.p->section->owner)))
+	 this by making the symbol appear to be undefined.
+
+	 NB: We change the previous definition in the IR object to
+	 undefweak only after all LTO symbols have been read.  */
+      else if (info->lto_all_symbols_read
+	       && (((h->type == bfd_link_hash_defweak
+		     || h->type == bfd_link_hash_defined)
+		    && is_ir_dummy_bfd (sym_bfd = h->u.def.section->owner))
+		   || (h->type == bfd_link_hash_common
+		       && is_ir_dummy_bfd (sym_bfd = h->u.c.p->section->owner))))
 	{
 	  h->type = bfd_link_hash_undefweak;
 	  h->u.undef.abfd = sym_bfd;

ld/testsuite/ld-plugin/lto.exp

@@ -210,6 +210,36 @@ set lto_link_tests [list \
   [list "Build pr26163a.o" \
    "" "-O2 -fno-lto" \
    {pr26163a.c}] \
+  [list "Build pr26262b.o" \
+   "" "-O2" \
+   {pr26262b.c} {} "" "c"] \
+  [list "Build pr26262c.o" \
+   "" "-O2" \
+   {pr26262c.c} {} "" "c"] \
+  [list "Build pr26267a.o" \
+   "" "-O2 -flto $lto_no_fat" \
+   {pr26267a.c} {} "" "c"] \
+  [list "Build pr26267b.o" \
+   "" "-O2" \
+   {pr26267b.c} {} "" "c"] \
+  [list "Build pr26267c.o" \
+   "" "-O2" \
+   {pr26267c.c} {} "" "c"] \
+  [list "Build pr26267a" \
+   "" "-O2" \
+   {pr26267a.c} {} "" "c"] \
+  [list "Build pr26267a" \
+   "-flto tmpdir/pr26267a.o tmpdir/pr26267b.o tmpdir/pr26267c.o" \
+   "-flto $lto_no_fat" \
+   {dummy.c} \
+   {{error_output "pr26267.err"}} \
+   "pr26267a"] \
+  [list "Build pr26267b" \
+   "-flto tmpdir/pr26267b.o tmpdir/pr26267c.o tmpdir/pr26267a.o" \
+   "-flto $lto_no_fat" \
+   {dummy.c} \
+   {{error_output "pr26267.err"}} \
+   "pr26267b"] \
 ]
 
 if { [at_least_gcc_version 10 0] } {
@@ -510,6 +540,16 @@ set lto_run_tests [list \
    {pr26163b.c} "pr24406-2" "pass.out" \
    "-flto -O2" "c" "" \
    "tmpdir/pr26163a.o -Wl,--defsym,g=real_g"] \
+  [list "Run pr26262a" \
+   "-O2 -flto" "" \
+   {pr26262a.c} "pr26262a" "pass.out" \
+   "-flto -O2" "c" "" \
+   "tmpdir/pr26262b.o tmpdir/pr26262c.o"] \
+  [list "Run pr26262b" \
+   "-flto -O2 tmpdir/pr26262b.o tmpdir/pr26262c.o" "" \
+   {pr26262a.c} "pr26262b" "pass.out" \
+   "-flto -O2" "c" "" \
+   ""] \
 ]
 
 if { [at_least_gcc_version 4 7] } {

ld/testsuite/ld-plugin/pr26262a.c

@@ -0,0 +1,21 @@
+#include <stdio.h>
+
+int counter;
+extern void foo (void);
+extern void xxx (void);
+
+void
+bar (void)
+{
+}
+
+int
+main(void)
+{
+  bar ();
+  foo ();
+  xxx ();
+  if (counter == 1)
+    printf ("PASS\n");
+  return 0;
+}

ld/testsuite/ld-plugin/pr26262b.c

@@ -0,0 +1,16 @@
+#include <stdlib.h>
+
+extern int counter;
+
+void
+foo (void)
+{
+  counter++;
+}
+
+__attribute__((weak))
+void
+bar (void)
+{
+  abort ();
+}

ld/testsuite/ld-plugin/pr26262c.c

@@ -0,0 +1,6 @@
+extern void bar (void);
+void
+xxx (void)
+{
+  bar ();
+}

ld/testsuite/ld-plugin/pr26267.err

@@ -0,0 +1,3 @@
+#...
+.*: multiple definition of `bar'; .*
+#...

ld/testsuite/ld-plugin/pr26267a.c

@@ -0,0 +1,21 @@
+#include <stdio.h>
+
+int counter;
+extern void foo (void);
+extern void xxx (void);
+
+void
+bar (void)
+{
+}
+
+int
+main(void)
+{
+  bar ();
+  foo ();
+  xxx ();
+  if (counter == 1)
+    printf ("PASS\n");
+  return 0;
+}

ld/testsuite/ld-plugin/pr26267b.c

@@ -0,0 +1,15 @@
+#include <stdlib.h>
+
+extern int counter;
+
+void
+foo (void)
+{
+  counter++;
+}
+
+void
+bar (void)
+{
+  abort ();
+}

ld/testsuite/ld-plugin/pr26267c.c

@@ -0,0 +1,6 @@
+extern void bar (void);
+void
+xxx (void)
+{
+  bar ();
+}