Avoid ubsan bug complaining about &p->field

I reckon it's quite OK to write &p->field in C when p might be NULL,
and lots of old C programmers probably agree with me.  However, ubsan
disagrees and so do some people I respect.  I suspect C++ influence is
to blame for the ubsan behaviour.  See
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92634.  So far no one has
educated me as to why I'm wrong to claim that there isn't anything in
the C standard to say that p->field is always (*p).field.  Note 79
doesn't quite do that because it doesn't cover null pointers.  If
there was such an equivalence then you could claim &p->field has a
null pointer reference when p is NULL, even though no C compiler would
ever dereference p.

Anyway, to silence ubsan I'm going to apply the following though I
prefer to avoid casts when possible.  And I'm using (void *)
deliberately because this is C, not C++!

	* ldlang.c (lang_output_section_find_by_flags): Don't use &p->field
	when p might be NULL.
	* ldelf.c (output_rel_find, ldelf_place_orphan): Likewise.
	(insert_os_after, lang_insert_orphan, lookup_name): Likewise.
	(strip_excluded_output_sections, lang_clear_os_map): Likewise.
	(lang_check, lang_for_each_input_file): Likewise.
	(lang_reset_memory_regions, find_replacements_insert_point): Likewise.
	(find_rescan_insertion, lang_propagate_lma_regions): Likewise.
	(lang_record_phdrs): Likewise.
	* emultempl/alphaelf.em (alpha_after_open): Likewise.
	* emultempl/mmo.em (mmo_place_orphan): Likewise.
	* emultempl/pe.em (gld_${EMULATION_NAME}_place_orphan): Likewise.
	* emultempl/pep.em (gld_${EMULATION_NAME}_place_orphan): Likewise.
	* emultempl/ppc32elf.em (ppc_after_check_relocs): Likewise.
	* emultempl/spuelf.em (spu_before_allocation): Likewise.
	(embedded_spu_file): Likewise.

1 files changed, 3 insertions, 3 deletions

diff --git a/ld/ldelf.c b/ld/ldelf.c
index b27917c..19ec908 100644
--- a/ld/ldelf.c
+++ b/ld/ldelf.c
@@ -1780,7 +1780,7 @@ output_rel_find (int isdyn, int rela)
   lang_output_section_statement_type *last_rel = NULL;
   lang_output_section_statement_type *last_rel_alloc = NULL;
 
-  for (lookup = &lang_os_list.head->output_section_statement;
+  for (lookup = (void *) lang_os_list.head;
        lookup != NULL;
        lookup = lookup->next)
     {
@@ -1952,7 +1952,7 @@ ldelf_place_orphan (asection *s, const char *secname, int constraint)
     {
       /* Find the output mbind section with the same type, attributes
 	 and sh_info field.  */
-      for (os = &lang_os_list.head->output_section_statement;
+      for (os = (void *) lang_os_list.head;
 	   os != NULL;
 	   os = os->next)
 	if (os->bfd_section != NULL
@@ -2129,7 +2129,7 @@ ldelf_place_orphan (asection *s, const char *secname, int constraint)
 					       _bfd_elf_match_sections_by_type);
       if (after == NULL)
 	/* *ABS* is always the first output section statement.  */
-	after = &lang_os_list.head->output_section_statement;
+	after = (void *) lang_os_list.head;
     }
 
   return lang_insert_orphan (s, secname, constraint, after, place, NULL, NULL);