[binutils-gdb/binutils-2_32-branch] PR24567, assertion failure in ldlang.c:6868 when compiling with -flto

[Alan Modra <amodra at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=f10648e0350707e0e51576c60f3f5b9cbb14ab75

commit f10648e0350707e0e51576c60f3f5b9cbb14ab75
Author: Alan Modra <amodra@gmail.com>
Date:   Fri May 17 19:09:42 2019 +0930

    PR24567, assertion failure in ldlang.c:6868 when compiling with -flto
    
    As the existing comment said: "a common ought to be overridden by a
    def in a -flto object".  This patch makes the code actually do that,
    rather than allowing a normal object file common to override a -flto
    defined symbol.
    
    	PR 24567
    	* plugin.c (plugin_notice): Do not let a common symbol override
    	a non-common definition in IR.
    
    (cherry picked from commit af4fa23fba220c1b26bb3c8a7996b406dcc181cc)

Diff:
---
 ld/ChangeLog |  6 ++++++
 ld/plugin.c  | 42 ++++++++++++++++++++++++------------------
 2 files changed, 30 insertions(+), 18 deletions(-)

diff --git a/ld/ChangeLog b/ld/ChangeLog
index 6add6bb..5ac2362 100644
--- a/ld/ChangeLog
+++ b/ld/ChangeLog
@@ -1,3 +1,9 @@
+2019-05-17  Alan Modra  <amodra@gmail.com>
+
+	PR 24567
+	* plugin.c (plugin_notice): Do not let a common symbol override
+	a non-common definition in IR.
+
 2019-04-18  Tamar Christina  <tamar.christina@arm.com>
 
 	Backport from mainline.
diff --git a/ld/plugin.c b/ld/plugin.c
index ea1a7f7..e4e781c 100644
--- a/ld/plugin.c
+++ b/ld/plugin.c
@@ -1316,30 +1316,36 @@ plugin_notice (struct bfd_link_info *info,
 	  ref = TRUE;
 	}
 
-      /* Otherwise, it must be a new def.  */
-      else
+
+      /* A common symbol should be merged with other commons or
+	 defs with the same name.  In particular, a common ought
+	 to be overridden by a def in a -flto object.  In that
+	 sense a common is also a ref.  */
+      else if (bfd_is_com_section (section))
 	{
-	  /* Ensure any symbol defined in an IR dummy BFD takes on a
-	     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.  */
-	  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)))
+	  if (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;
 	    }
+	  ref = TRUE;
+	}
 
-	  /* A common symbol should be merged with other commons or
-	     defs with the same name.  In particular, a common ought
-	     to be overridden by a def in a -flto object.  In that
-	     sense a common is also a ref.  */
-	  if (bfd_is_com_section (section))
-	    ref = TRUE;
+      /* Otherwise, it must be a new def.
+	 Ensure any symbol defined in an IR dummy BFD takes on a
+	 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)))
+	{
+	  h->type = bfd_link_hash_undefweak;
+	  h->u.undef.abfd = sym_bfd;
 	}
 
       if (ref)