PR24311, FAIL: S-records with constructors

Not padding string merge section output to its alignment can cause
failures of the S-record tests when input string merge sections are
padded, since the ELF linker output for the single string section
would shrink compared to the SREC linker output.  That might result in
following sections having different addresses.
On the other hand, padding string merge section output when input
string merge sections are *not* padded can also cause failures, in
this case due to the ELF linker output for the string section being
larger (due to padding) than the SREC linker output.

It would be better to write a more robust test, but it is also nice
to leave input unchanged when no string merges occur.

	PR 24311
	* merge.c (merge_strings): Return secinfo.  Don't pad section
	to alignment here.
	(_bfd_merge_sections): Pad section to alignment here, if input
	sections contributing to merged output all pad to alignment.
	Formatting.

2 files changed, 39 insertions, 22 deletions

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 15a5a99..18f1804 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,12 @@
+2019-03-08  Alan Modra  <amodra@gmail.com>
+
+	PR 24311
+	* merge.c (merge_strings): Return secinfo.  Don't pad section
+	to alignment here.
+	(_bfd_merge_sections): Pad section to alignment here, if input
+	sections contributing to merged output all pad to alignment.
+	Formatting.
+
 2019-03-06  Nick Clifton  <nickc@redhat.com>
 
 	* dwarf2.c (_bfd_dwarf2_find_symbol_bias): Check for a NULL symbol
diff --git a/bfd/merge.c b/bfd/merge.c
index fb7c085..632c852 100644
--- a/bfd/merge.c
+++ b/bfd/merge.c
@@ -621,7 +621,7 @@ is_suffix (const struct sec_merge_hash_entry *A,
 
 /* This is a helper function for _bfd_merge_sections.  It attempts to
    merge strings matching suffixes of longer strings.  */
-static bfd_boolean
+static struct sec_merge_sec_info *
 merge_strings (struct sec_merge_info *sinfo)
 {
   struct sec_merge_hash_entry **array, **a, *e;
@@ -633,7 +633,7 @@ merge_strings (struct sec_merge_info *sinfo)
   amt = sinfo->htab->size * sizeof (struct sec_merge_hash_entry *);
   array = (struct sec_merge_hash_entry **) bfd_malloc (amt);
   if (array == NULL)
-    return FALSE;
+    return NULL;
 
   for (e = sinfo->htab->first, a = array; e; e = e->next)
     if (e->alignment)
@@ -703,11 +703,6 @@ merge_strings (struct sec_merge_info *sinfo)
 	}
     }
   secinfo->sec->size = size;
-  if (secinfo->sec->alignment_power != 0)
-    {
-      bfd_size_type align = (bfd_size_type) 1 << secinfo->sec->alignment_power;
-      secinfo->sec->size = (secinfo->sec->size + align - 1) & -align;
-    }
 
   /* And now adjust the rest, removing them from the chain (but not hashtable)
      at the same time.  */
@@ -724,7 +719,7 @@ merge_strings (struct sec_merge_info *sinfo)
 	    e->u.index = e->u.suffix->u.index + (e->u.suffix->len - e->len);
 	  }
       }
-  return TRUE;
+  return secinfo;
 }
 
 /* This function is called once after all SEC_MERGE sections are registered
@@ -740,7 +735,8 @@ _bfd_merge_sections (bfd *abfd,
 
   for (sinfo = (struct sec_merge_info *) xsinfo; sinfo; sinfo = sinfo->next)
     {
-      struct sec_merge_sec_info * secinfo;
+      struct sec_merge_sec_info *secinfo;
+      bfd_size_type align;
 
       if (! sinfo->chain)
 	continue;
@@ -751,6 +747,7 @@ _bfd_merge_sections (bfd *abfd,
       secinfo->next = NULL;
 
       /* Record the sections into the hash table.  */
+      align = 1;
       for (secinfo = sinfo->chain; secinfo; secinfo = secinfo->next)
 	if (secinfo->sec->flags & SEC_EXCLUDE)
 	  {
@@ -758,18 +755,25 @@ _bfd_merge_sections (bfd *abfd,
 	    if (remove_hook)
 	      (*remove_hook) (abfd, secinfo->sec);
 	  }
-	else if (! record_section (sinfo, secinfo))
-	  return FALSE;
-
-      if (secinfo)
-	continue;
+	else
+	  {
+	    if (!record_section (sinfo, secinfo))
+	      return FALSE;
+	    if (align)
+	      {
+		align = (bfd_size_type) 1 << secinfo->sec->alignment_power;
+		if ((secinfo->sec->size & (align - 1)) != 0)
+		  align = 0;
+	      }
+	  }
 
       if (sinfo->htab->first == NULL)
 	continue;
 
       if (sinfo->htab->strings)
 	{
-	  if (!merge_strings (sinfo))
+	  secinfo = merge_strings (sinfo);
+	  if (!secinfo)
 	    return FALSE;
 	}
       else
@@ -789,8 +793,7 @@ _bfd_merge_sections (bfd *abfd,
 		  e->secinfo->first_str = e;
 		  size = 0;
 		}
-	      size = (size + e->alignment - 1)
-		     & ~((bfd_vma) e->alignment - 1);
+	      size = (size + e->alignment - 1) & ~((bfd_vma) e->alignment - 1);
 	      e->u.index = size;
 	      size += e->len;
 	      secinfo = e->secinfo;
@@ -798,11 +801,16 @@ _bfd_merge_sections (bfd *abfd,
 	  secinfo->sec->size = size;
 	}
 
-	/* Finally remove all input sections which have not made it into
-	   the hash table at all.  */
-	for (secinfo = sinfo->chain; secinfo; secinfo = secinfo->next)
-	  if (secinfo->first_str == NULL)
-	    secinfo->sec->flags |= SEC_EXCLUDE | SEC_KEEP;
+      /* If the input sections were padded according to their alignments,
+	 then pad the output too.  */
+      if (align)
+	secinfo->sec->size = (secinfo->sec->size + align - 1) & -align;
+
+      /* Finally remove all input sections which have not made it into
+	 the hash table at all.  */
+      for (secinfo = sinfo->chain; secinfo; secinfo = secinfo->next)
+	if (secinfo->first_str == NULL)
+	  secinfo->sec->flags |= SEC_EXCLUDE | SEC_KEEP;
     }
 
   return TRUE;