Avoid ubsan bug complaining about &p->field

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Avoid ubsan bug complaining about &p->field

Alan Modra-3
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.

diff --git a/ld/emultempl/alphaelf.em b/ld/emultempl/alphaelf.em
index 4e7886fcd6..db53d515ed 100644
--- a/ld/emultempl/alphaelf.em
+++ b/ld/emultempl/alphaelf.em
@@ -47,7 +47,7 @@ alpha_after_open (void)
       lang_output_section_statement_type *plt_os[2];
 
       num_plt = 0;
-      for (os = &lang_os_list.head->output_section_statement;
+      for (os = (void *) lang_os_list.head;
    os != NULL;
    os = os->next)
  {
diff --git a/ld/emultempl/mmo.em b/ld/emultempl/mmo.em
index 85c5863953..247d8a8c0b 100644
--- a/ld/emultempl/mmo.em
+++ b/ld/emultempl/mmo.em
@@ -163,7 +163,7 @@ mmo_place_orphan (asection *s,
 
   /* We have to find the oss before this one, so we can use that as
      "after".  */
-  for (lookup = &lang_os_list.head->output_section_statement;
+  for (lookup = (void *) lang_os_list.head;
        lookup != NULL && lookup->next != before;
        lookup = lookup->next)
     ;
diff --git a/ld/emultempl/pe.em b/ld/emultempl/pe.em
index c4c6464c3c..7e85ede3e2 100644
--- a/ld/emultempl/pe.em
+++ b/ld/emultempl/pe.em
@@ -2151,7 +2151,7 @@ gld_${EMULATION_NAME}_place_orphan (asection *s,
        NULL);
   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;
  }
 
       /* All sections in an executable must be aligned to a page boundary.
diff --git a/ld/emultempl/pep.em b/ld/emultempl/pep.em
index ec2d83fa63..f9f6a8e98d 100644
--- a/ld/emultempl/pep.em
+++ b/ld/emultempl/pep.em
@@ -1950,7 +1950,7 @@ gld_${EMULATION_NAME}_place_orphan (asection *s,
        NULL);
   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;
  }
 
       /* All sections in an executable must be aligned to a page boundary.
diff --git a/ld/emultempl/ppc32elf.em b/ld/emultempl/ppc32elf.em
index 056068edb1..78a2eb1cfa 100644
--- a/ld/emultempl/ppc32elf.em
+++ b/ld/emultempl/ppc32elf.em
@@ -79,7 +79,7 @@ ppc_after_check_relocs (void)
 
       num_got = 0;
       num_plt = 0;
-      for (os = &lang_os_list.head->output_section_statement;
+      for (os = (void *) lang_os_list.head;
    os != NULL;
    os = os->next)
  {
diff --git a/ld/emultempl/spuelf.em b/ld/emultempl/spuelf.em
index 40a757a989..96ac86f3f2 100644
--- a/ld/emultempl/spuelf.em
+++ b/ld/emultempl/spuelf.em
@@ -290,7 +290,7 @@ spu_before_allocation (void)
     }
 
   /* Ensure alignment of overlay sections is sufficient.  */
-  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
@@ -512,7 +512,7 @@ embedded_spu_file (lang_input_statement_type *entry, const char *flags)
     return FALSE;
   close (fd);
 
-  for (search = &input_file_chain.head->input_statement;
+  for (search = (void *) input_file_chain.head;
        search != NULL;
        search = search->next_real_file)
     if (search->filename != NULL)
diff --git a/ld/ldelf.c b/ld/ldelf.c
index b27917c5fc..19ec9085e6 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);
diff --git a/ld/ldlang.c b/ld/ldlang.c
index 05ea0c881f..1106ab145f 100644
--- a/ld/ldlang.c
+++ b/ld/ldlang.c
@@ -1552,7 +1552,7 @@ lang_output_section_find_by_flags (const asection *sec,
 
   /* We know the first statement on this list is *ABS*.  May as well
      skip it.  */
-  first = &lang_os_list.head->output_section_statement;
+  first = (void *) lang_os_list.head;
   first = first->next;
 
   /* First try for an exact match.  */
@@ -1780,7 +1780,7 @@ insert_os_after (lang_output_section_statement_type *after)
   lang_statement_union_type **assign = NULL;
   bfd_boolean ignore_first;
 
-  ignore_first = after == &lang_os_list.head->output_section_statement;
+  ignore_first = after == (void *) lang_os_list.head;
 
   for (where = &after->header.next;
        *where != NULL;
@@ -1904,7 +1904,7 @@ lang_insert_orphan (asection *s,
       /* Shuffle the bfd section list to make the output file look
  neater.  This is really only cosmetic.  */
       if (place->section == NULL
-  && after != &lang_os_list.head->output_section_statement)
+  && after != (void *) lang_os_list.head)
  {
   asection *bfd_section = after->bfd_section;
 
@@ -2846,7 +2846,7 @@ lookup_name (const char *name)
 {
   lang_input_statement_type *search;
 
-  for (search = &input_file_chain.head->input_statement;
+  for (search = (void *) input_file_chain.head;
        search != NULL;
        search = search->next_real_file)
     {
@@ -4329,7 +4329,7 @@ strip_excluded_output_sections (void)
       lang_reset_memory_regions ();
     }
 
-  for (os = &lang_os_list.head->output_section_statement;
+  for (os = (void *) lang_os_list.head;
        os != NULL;
        os = os->next)
     {
@@ -4390,7 +4390,7 @@ lang_clear_os_map (void)
   if (map_head_is_link_order)
     return;
 
-  for (os = &lang_os_list.head->output_section_statement;
+  for (os = (void *) lang_os_list.head;
        os != NULL;
        os = os->next)
     {
@@ -6728,7 +6728,7 @@ lang_check (void)
   bfd *input_bfd;
   const bfd_arch_info_type *compatible;
 
-  for (file = &file_chain.head->input_statement;
+  for (file = (void *) file_chain.head;
        file != NULL;
        file = file->next)
     {
@@ -7070,7 +7070,7 @@ lang_for_each_input_file (void (*func) (lang_input_statement_type *))
 {
   lang_input_statement_type *f;
 
-  for (f = &input_file_chain.head->input_statement;
+  for (f = (void *) input_file_chain.head;
        f != NULL;
        f = f->next_real_file)
     if (f->flags.real)
@@ -7196,7 +7196,7 @@ lang_reset_memory_regions (void)
       p->last_os = NULL;
     }
 
-  for (os = &lang_os_list.head->output_section_statement;
+  for (os = (void *) lang_os_list.head;
        os != NULL;
        os = os->next)
     {
@@ -7433,8 +7433,8 @@ static lang_input_statement_type *
 find_replacements_insert_point (bfd_boolean *before)
 {
   lang_input_statement_type *claim1, *lastobject;
-  lastobject = &input_file_chain.head->input_statement;
-  for (claim1 = &file_chain.head->input_statement;
+  lastobject = (void *) input_file_chain.head;
+  for (claim1 = (void *) file_chain.head;
        claim1 != NULL;
        claim1 = claim1->next)
     {
@@ -7476,7 +7476,7 @@ find_rescan_insertion (lang_input_statement_type *add)
      file chain if it is full of archive elements.  Archives don't
      appear on the file chain, but if an element has been extracted
      then their input_statement->next points at it.  */
-  for (f = &input_file_chain.head->input_statement;
+  for (f = (void *) input_file_chain.head;
        f != NULL;
        f = f->next_real_file)
     {
@@ -7609,7 +7609,7 @@ lang_propagate_lma_regions (void)
 {
   lang_output_section_statement_type *os;
 
-  for (os = &lang_os_list.head->output_section_statement;
+  for (os = (void *) lang_os_list.head;
        os != NULL;
        os = os->next)
     {
@@ -8286,7 +8286,7 @@ lang_record_phdrs (void)
       bfd_vma at;
 
       c = 0;
-      for (os = &lang_os_list.head->output_section_statement;
+      for (os = (void *) lang_os_list.head;
    os != NULL;
    os = os->next)
  {
@@ -8372,7 +8372,7 @@ lang_record_phdrs (void)
   free (secs);
 
   /* Make sure all the phdr assignments succeeded.  */
-  for (os = &lang_os_list.head->output_section_statement;
+  for (os = (void *) lang_os_list.head;
        os != NULL;
        os = os->next)
     {

--
Alan Modra
Australia Development Lab, IBM