Re: [PATCH 12/24] gdb: make solib-svr4 not use so_list internally

[Lancelot SIX <lsix@lancelotsix.com>]

Hi Simon,

When applying this patch, I have:

Applying: gdb: make solib-svr4 not use so_list internally
.git/rebase-apply/patch:182: trailing whitespace.
               sizeof (newobj->so_name) - 1);                                                                                                                
.git/rebase-apply/patch:183: trailing whitespace.
      newobj->so_name[sizeof (newobj->so_name) - 1] = 0;                                                                                                                            
.git/rebase-apply/patch:184: trailing whitespace.
      strcpy (newobj->so_original_name, newobj->so_name);    
warning: 3 lines add whitespace errors.

I only skimmed through the patch, I have not payed detailed attention to
details so far.

Best,
Lancelot.

On Tue, Oct 10, 2023 at 04:40:07PM -0400, Simon Marchi wrote:
> A subsequent patch makes use of non-trivial types in struct so_list.
> This trips on the fact that svr4_copy_library_list uses memcpy to copy
> so_list objects:
> 
>       so_list *newobj = new so_list;
>       memcpy (newobj, src, sizeof (struct so_list));
> 
> solib-svr4 maintains lists of so_list objects in its own internal data
> structures.  When requested to return a list of so_list objects (through
> target_so_ops::current_sos), it duplicates the internal so_list lists,
> using memcpy.  When changing so_list to make it non-trivial, we would
> need to replace this use of memcpy somehow.  That would mean making
> so_list copyable, with all the complexity that entails, just to satisfy
> this internal usage of solib-svr4 (and solib-rocm, which does the same).
> 
> Change solib-svr4 to use its own data type for its internal lists.  The
> use of so_list is a bit overkill anyway, as most fields of so_list are
> irrelevant for this internal use.
> 
>  - Introduce svr4_so, which contains just an std::string for the name
>    and a unique_ptr for the lm_info.
>  - Change the internal so_list lists to be std::vector<svr4_so>.  Vector
>    seems like a good choice for this, we don't need to insert/remove
>    elements in the middle of these internal lists.
>  - Remove svr4_free_library_list, free_solib_lists and ~svr4_info, as
>    everything is managed automatically now.
>  - Replace svr4_copy_library_list (which duplicated internal lists in
>    order to return them to the core) with so_list_from_svr4_sos, which
>    creates an so_list list from a vector of svr4_so.
>  - Generalize svr4_same a bit, because find_debug_base_for_solib now
>    needs to compare an so_list and an svr4_so to see if they are the
>    same.
> 
> Change-Id: I6012e48e07aace2a8172b74b389f9547ce777877
> ---
>  gdb/solib-svr4.c | 275 +++++++++++++++++------------------------------
>  gdb/solib-svr4.h |   2 +
>  2 files changed, 100 insertions(+), 177 deletions(-)
> 
> diff --git a/gdb/solib-svr4.c b/gdb/solib-svr4.c
> index 7d247fa455e9..9266929d2895 100644
> --- a/gdb/solib-svr4.c
> +++ b/gdb/solib-svr4.c
> @@ -50,7 +50,6 @@
>  static struct link_map_offsets *svr4_fetch_link_map_offsets (void);
>  static int svr4_have_link_map_offsets (void);
>  static void svr4_relocate_main_executable (void);
> -static void svr4_free_library_list (so_list *solist);
>  static void probes_table_remove_objfile_probes (struct objfile *objfile);
>  static void svr4_iterate_over_objfiles_in_search_order
>    (gdbarch *gdbarch, iterate_over_objfiles_in_search_order_cb_ftype cb,
> @@ -172,26 +171,35 @@ svr4_same_1 (const char *gdb_so_name, const char *inferior_so_name)
>    return 0;
>  }
>  
> -static int
> -svr4_same (const so_list &gdb, const so_list &inferior)
> +static bool
> +svr4_same (const char *gdb_name, const char *inferior_name,
> +	   const lm_info_svr4 &gdb_lm_info,
> +	   const lm_info_svr4 &inferior_lm_info)
>  {
> -  if (!svr4_same_1 (gdb.so_original_name, inferior.so_original_name))
> +  if (!svr4_same_1 (gdb_name, inferior_name))
>      return false;
>  
>    /* There may be different instances of the same library, in different
>       namespaces.  Each instance, however, must have been loaded at a
>       different address so its relocation offset would be different.  */
> +  return gdb_lm_info.l_addr_inferior == inferior_lm_info.l_addr_inferior;
> +}
> +
> +static int
> +svr4_same (const so_list &gdb, const so_list &inferior)
> +{
>    auto *lmg = gdb::checked_static_cast<const lm_info_svr4 *> (gdb.lm_info);
>    auto *lmi = gdb::checked_static_cast<const lm_info_svr4 *> (inferior.lm_info);
>  
> -  return (lmg->l_addr_inferior == lmi->l_addr_inferior);
> +  return svr4_same (gdb.so_original_name, inferior.so_original_name,
> +		    *lmg, *lmi);
>  }
>  
> -static std::unique_ptr<lm_info_svr4>
> +static lm_info_svr4_up
>  lm_info_read (CORE_ADDR lm_addr)
>  {
>    struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
> -  std::unique_ptr<lm_info_svr4> lm_info;
> +  lm_info_svr4_up lm_info;
>  
>    gdb::byte_vector lm (lmo->link_map_size);
>  
> @@ -203,7 +211,7 @@ lm_info_read (CORE_ADDR lm_addr)
>        type *ptr_type
>  	= builtin_type (current_inferior ()->arch ())->builtin_data_ptr;
>  
> -      lm_info.reset (new lm_info_svr4);
> +      lm_info = gdb::make_unique<lm_info_svr4> ();
>        lm_info->lm_addr = lm_addr;
>  
>        lm_info->l_addr_inferior = extract_typed_address (&lm[lmo->l_addr_offset],
> @@ -333,13 +341,20 @@ lm_addr_check (const so_list &so, bfd *abfd)
>    return li->l_addr;
>  }
>  
> +struct svr4_so
> +{
> +  svr4_so (const char *name, lm_info_svr4_up lm_info)
> +    : name (name), lm_info (std::move (lm_info))
> +  {}
> +
> +  std::string name;
> +  lm_info_svr4_up lm_info;
> +};
> +
>  /* Per pspace SVR4 specific data.  */
>  
>  struct svr4_info
>  {
> -  svr4_info () = default;
> -  ~svr4_info ();
> -
>    /* Base of dynamic linker structures in default namespace.  */
>    CORE_ADDR debug_base = 0;
>  
> @@ -385,7 +400,7 @@ struct svr4_info
>  
>       The special entry zero is reserved for a linear list to support
>       gdbstubs that do not support namespaces.  */
> -  std::map<CORE_ADDR, so_list *> solib_lists;
> +  std::map<CORE_ADDR, std::vector<svr4_so>> solib_lists;
>  };
>  
>  /* Per-program-space data key.  */
> @@ -407,23 +422,6 @@ free_probes_table (struct svr4_info *info)
>    info->probes_table.reset (nullptr);
>  }
>  
> -/* Free the solib lists for all namespaces.  */
> -
> -static void
> -free_solib_lists (svr4_info *info)
> -{
> -  for (const std::pair<CORE_ADDR, so_list *> tuple
> -	 : info->solib_lists)
> -    svr4_free_library_list (tuple.second);
> -
> -  info->solib_lists.clear ();
> -}
> -
> -svr4_info::~svr4_info ()
> -{
> -  free_solib_lists (this);
> -}
> -
>  /* Get the svr4 data for program space PSPACE.  If none is found yet, add it now.
>     This function always returns a valid object.  */
>  
> @@ -955,7 +953,7 @@ struct svr4_library_list
>  {
>    /* The tail pointer of the current namespace.  This is internal to XML
>       parsing.  */
> -  so_list **tailp;
> +  std::vector<svr4_so> *cur_list;
>  
>    /* Inferior address of struct link_map used for the main executable.  It is
>       NULL if not known.  */
> @@ -965,7 +963,7 @@ struct svr4_library_list
>       not include any default sos.
>  
>       See comment on struct svr4_info.solib_lists.  */
> -  std::map<CORE_ADDR, so_list *> solib_lists;
> +  std::map<CORE_ADDR, std::vector<svr4_so>> solib_lists;
>  };
>  
>  /* This module's 'free_objfile' observer.  */
> @@ -987,41 +985,27 @@ svr4_clear_so (const so_list &so)
>      li->l_addr_p = 0;
>  }
>  
> -/* Free so_list built so far.  */
> -
> -static void
> -svr4_free_library_list (so_list *list)
> -{
> -  while (list != NULL)
> -    {
> -      struct so_list *next = list->next;
> +/* Create the so_list objects equivalent to the svr4_sos in SOS.  */
>  
> -      free_so (*list);
> -      list = next;
> -    }
> -}
> -
> -/* Copy library list.  */
> -
> -static struct so_list *
> -svr4_copy_library_list (struct so_list *src)
> +static so_list *
> +so_list_from_svr4_sos (const std::vector<svr4_so> &sos)
>  {
>    struct so_list *dst = NULL;
>    struct so_list **link = &dst;
>  
> -  while (src != NULL)
> +  for (const svr4_so &so : sos)
>      {
>        so_list *newobj = new so_list;
> -      memcpy (newobj, src, sizeof (struct so_list));
>  
> -      auto *src_li = gdb::checked_static_cast<lm_info_svr4 *> (src->lm_info);
> -      newobj->lm_info = new lm_info_svr4 (*src_li);
> +      strncpy (newobj->so_name, so.name.c_str (),
> +	       sizeof (newobj->so_name) - 1);                                                                                                                
> +      newobj->so_name[sizeof (newobj->so_name) - 1] = 0;                                                                                                                            
> +      strcpy (newobj->so_original_name, newobj->so_name);    
> +      newobj->lm_info = new lm_info_svr4 (*so.lm_info);
>  
>        newobj->next = NULL;
>        *link = newobj;
>        link = &newobj->next;
> -
> -      src = src->next;
>      }
>  
>    return dst;
> @@ -1050,48 +1034,25 @@ library_list_start_library (struct gdb_xml_parser *parser,
>    ULONGEST *l_ldp
>      = (ULONGEST *) xml_find_attribute (attributes, "l_ld")->value.get ();
>  
> -  so_list *new_elem = new so_list;
> -  lm_info_svr4 *li = new lm_info_svr4;
> -  new_elem->lm_info = li;
> +  lm_info_svr4_up li = gdb::make_unique<lm_info_svr4> ();
>    li->lm_addr = *lmp;
>    li->l_addr_inferior = *l_addrp;
>    li->l_ld = *l_ldp;
>  
> -  strncpy (new_elem->so_name, name, sizeof (new_elem->so_name) - 1);
> -  new_elem->so_name[sizeof (new_elem->so_name) - 1] = 0;
> -  strcpy (new_elem->so_original_name, new_elem->so_name);
> +  std::vector<svr4_so> *solist;
>  
>    /* Older versions did not supply lmid.  Put the element into the flat
>       list of the special namespace zero in that case.  */
>    gdb_xml_value *at_lmid = xml_find_attribute (attributes, "lmid");
>    if (at_lmid == nullptr)
> -    {
> -      *list->tailp = new_elem;
> -      list->tailp = &new_elem->next;
> -    }
> +    solist = list->cur_list;
>    else
>      {
>        ULONGEST lmid = *(ULONGEST *) at_lmid->value.get ();
> -
> -      /* Ensure that the element is actually initialized.  */
> -      if (list->solib_lists.find (lmid) == list->solib_lists.end ())
> -	list->solib_lists[lmid] = nullptr;
> -
> -      so_list **psolist = &list->solib_lists[lmid];
> -      so_list **pnext = psolist;
> -
> -      /* Walk to the end of the list if we have one.  */
> -      so_list *solist = *psolist;
> -      if (solist != nullptr)
> -	{
> -	  for (; solist->next != nullptr; solist = solist->next)
> -	    /* Nothing.  */;
> -
> -	  pnext = &solist->next;
> -	}
> -
> -      *pnext = new_elem;
> +      solist = &list->solib_lists[lmid];
>      }
> +
> +  solist->emplace_back (name, std::move (li));
>  }
>  
>  /* Handle the start of a <library-list-svr4> element.  */
> @@ -1117,9 +1078,7 @@ svr4_library_list_start_list (struct gdb_xml_parser *parser,
>  
>    /* Older gdbserver do not support namespaces.  We use the special
>       namespace zero for a linear list of libraries.  */
> -  so_list **solist = &list->solib_lists[0];
> -  *solist = nullptr;
> -  list->tailp = solist;
> +  list->cur_list = &list->solib_lists[0];
>  }
>  
>  /* The allowed elements and attributes for an XML library list.
> @@ -1169,13 +1128,9 @@ static int
>  svr4_parse_libraries (const char *document, struct svr4_library_list *list)
>  {
>    auto cleanup = make_scope_exit ([list] ()
> -    {
> -      for (const std::pair<CORE_ADDR, so_list *> tuple
> -	     : list->solib_lists)
> -	svr4_free_library_list (tuple.second);
> -    });
> +    {  list->solib_lists.clear (); });
>  
> -  list->tailp = nullptr;
> +  list->cur_list = nullptr;
>    list->main_lm = 0;
>    list->solib_lists.clear ();
>    if (gdb_xml_parse_quick (_("target library list"), "library-list-svr4.dtd",
> @@ -1253,25 +1208,21 @@ svr4_default_sos (svr4_info *info)
>  
>  /* Read the whole inferior libraries chain starting at address LM.
>     Expect the first entry in the chain's previous entry to be PREV_LM.
> -   Add the entries to the tail referenced by LINK_PTR_PTR.  Ignore the
> -   first entry if IGNORE_FIRST and set global MAIN_LM_ADDR according
> -   to it.  Returns nonzero upon success.  If zero is returned the
> -   entries stored to LINK_PTR_PTR are still valid although they may
> +   Add the entries to SOS.  Ignore the first entry if IGNORE_FIRST and set
> +   global MAIN_LM_ADDR according to it.  Returns nonzero upon success.  If zero
> +   is returned the entries stored to LINK_PTR_PTR are still valid although they may
>     represent only part of the inferior library list.  */
>  
>  static int
>  svr4_read_so_list (svr4_info *info, CORE_ADDR lm, CORE_ADDR prev_lm,
> -		   struct so_list ***link_ptr_ptr, int ignore_first)
> +		   std::vector<svr4_so> &sos, int ignore_first)
>  {
>    CORE_ADDR first_l_name = 0;
>    CORE_ADDR next_lm;
>  
>    for (; lm != 0; prev_lm = lm, lm = next_lm)
>      {
> -      so_list_up newobj (new so_list);
> -
> -      lm_info_svr4 *li = lm_info_read (lm).release ();
> -      newobj->lm_info = li;
> +      lm_info_svr4_up li = lm_info_read (lm);
>        if (li == NULL)
>  	return 0;
>  
> @@ -1298,9 +1249,9 @@ svr4_read_so_list (svr4_info *info, CORE_ADDR lm, CORE_ADDR prev_lm,
>  	}
>  
>        /* Extract this shared object's name.  */
> -      gdb::unique_xmalloc_ptr<char> buffer
> +      gdb::unique_xmalloc_ptr<char> name
>  	= target_read_string (li->l_name, SO_NAME_MAX_PATH_SIZE - 1);
> -      if (buffer == nullptr)
> +      if (name == nullptr)
>  	{
>  	  /* If this entry's l_name address matches that of the
>  	     inferior executable, then this is not a normal shared
> @@ -1311,19 +1262,12 @@ svr4_read_so_list (svr4_info *info, CORE_ADDR lm, CORE_ADDR prev_lm,
>  	  continue;
>  	}
>  
> -      strncpy (newobj->so_name, buffer.get (), SO_NAME_MAX_PATH_SIZE - 1);
> -      newobj->so_name[SO_NAME_MAX_PATH_SIZE - 1] = '\0';
> -      strcpy (newobj->so_original_name, newobj->so_name);
> -
>        /* If this entry has no name, or its name matches the name
>  	 for the main executable, don't include it in the list.  */
> -      if (! newobj->so_name[0] || match_main (newobj->so_name))
> +      if (*name == '\0' || match_main (name.get ()))
>  	continue;
>  
> -      newobj->next = 0;
> -      /* Don't free it now.  */
> -      **link_ptr_ptr = newobj.release ();
> -      *link_ptr_ptr = &(**link_ptr_ptr)->next;
> +      sos.emplace_back (name.get (), std::move (li));
>      }
>  
>    return 1;
> @@ -1342,7 +1286,7 @@ svr4_current_sos_direct (struct svr4_info *info)
>    struct svr4_library_list library_list;
>  
>    /* Remove any old libraries.  We're going to read them back in again.  */
> -  free_solib_lists (info);
> +  info->solib_lists.clear ();
>  
>    /* Fall back to manual examination of the target if the packet is not
>       supported or gdbserver failed to find DT_DEBUG.  gdb.server/solib-list.exp
> @@ -1362,10 +1306,10 @@ svr4_current_sos_direct (struct svr4_info *info)
>        /* Remove an empty special zero namespace so we know that when there
>  	 is one, it is actually used, and we have a flat list without
>  	 namespace information.  */
> -      if ((library_list.solib_lists.find (0)
> -	   != library_list.solib_lists.end ())
> -	  && (library_list.solib_lists[0] == nullptr))
> -	library_list.solib_lists.erase (0);
> +      auto it_0 = library_list.solib_lists.find (0);
> +      if (it_0 != library_list.solib_lists.end ()
> +	  && it_0->second.empty ())
> +	library_list.solib_lists.erase (it_0);
>  
>        /* Replace the (empty) solib_lists in INFO with the one generated
>  	 from the target.  We don't want to copy it on assignment and then
> @@ -1391,9 +1335,7 @@ svr4_current_sos_direct (struct svr4_info *info)
>      ignore_first = true;
>  
>    auto cleanup = make_scope_exit ([info] ()
> -    {
> -      free_solib_lists (info);
> -    });
> +    { info->solib_lists.clear (); });
>  
>    /* Collect the sos in each namespace.  */
>    CORE_ADDR debug_base = info->debug_base;
> @@ -1403,12 +1345,8 @@ svr4_current_sos_direct (struct svr4_info *info)
>        /* Walk the inferior's link map list, and build our so_list list.  */
>        lm = solib_svr4_r_map (debug_base);
>        if (lm != 0)
> -	{
> -	  so_list **sos = &info->solib_lists[debug_base];
> -	  *sos = nullptr;
> -
> -	  svr4_read_so_list (info, lm, 0, &sos, ignore_first);
> -	}
> +	svr4_read_so_list (info, lm, 0, info->solib_lists[debug_base],
> +			   ignore_first);
>      }
>  
>    /* On Solaris, the dynamic linker is not in the normal list of
> @@ -1425,11 +1363,8 @@ svr4_current_sos_direct (struct svr4_info *info)
>      {
>        /* Add the dynamic linker's namespace unless we already did.  */
>        if (info->solib_lists.find (debug_base) == info->solib_lists.end ())
> -	{
> -	  so_list **sos = &info->solib_lists[debug_base];
> -	  *sos = nullptr;
> -	  svr4_read_so_list (info, debug_base, 0, &sos, 0);
> -	}
> +	svr4_read_so_list (info, debug_base, 0, info->solib_lists[debug_base],
> +			   0);
>      }
>  
>    cleanup.release ();
> @@ -1440,19 +1375,18 @@ svr4_current_sos_direct (struct svr4_info *info)
>  static so_list *
>  svr4_collect_probes_sos (svr4_info *info)
>  {
> -  so_list *sos = nullptr;
> -  so_list **pnext = &sos;
> +  so_list *res = nullptr;
> +  so_list **pnext = &res;
>  
> -  for (const std::pair<CORE_ADDR, so_list *> tuple
> -	 : info->solib_lists)
> +  for (const auto &tuple : info->solib_lists)
>      {
> -      so_list *solist = tuple.second;
> +      const std::vector<svr4_so> &sos = tuple.second;
>  
>        /* Allow the linker to report empty namespaces.  */
> -      if (solist == nullptr)
> +      if (sos.empty ())
>  	continue;
>  
> -      *pnext = svr4_copy_library_list (solist);
> +      *pnext = so_list_from_svr4_sos (sos);
>  
>        /* Update PNEXT to point to the next member of the last element.  */
>        gdb_assert (*pnext != nullptr);
> @@ -1466,7 +1400,7 @@ svr4_collect_probes_sos (svr4_info *info)
>  	}
>      }
>  
> -  return sos;
> +  return res;
>  }
>  
>  /* Implement the main part of the "current_sos" target_so_ops
> @@ -1853,16 +1787,10 @@ solist_update_incremental (svr4_info *info, CORE_ADDR debug_base,
>    if (info->solib_lists.find (0) != info->solib_lists.end ())
>      return 0;
>  
> -  /* Ensure that the element is actually initialized.  */
> -  if (info->solib_lists.find (debug_base) == info->solib_lists.end ())
> -    info->solib_lists[debug_base] = nullptr;
> -
> -  so_list **psolist = &info->solib_lists[debug_base];
> -  so_list **pnext = nullptr;
> -  so_list *solist = *psolist;
> +  std::vector<svr4_so> &solist = info->solib_lists[debug_base];
>    CORE_ADDR prev_lm;
>  
> -  if (solist == nullptr)
> +  if (solist.empty ())
>      {
>        /* svr4_current_sos_direct contains logic to handle a number of
>  	 special cases relating to the first elements of the list in
> @@ -1872,18 +1800,9 @@ solist_update_incremental (svr4_info *info, CORE_ADDR debug_base,
>  	return 0;
>  
>        prev_lm = 0;
> -      pnext = psolist;
>      }
>    else
> -    {
> -      /* Walk to the end of the list.  */
> -      for (; solist->next != nullptr; solist = solist->next)
> -	/* Nothing.  */;
> -
> -      auto *li = gdb::checked_static_cast<lm_info_svr4 *> (solist->lm_info);
> -      prev_lm = li->lm_addr;
> -      pnext = &solist->next;
> -    }
> +    prev_lm = solist.back ().lm_info->lm_addr;
>  
>    /* Read the new objects.  */
>    if (info->using_xfer)
> @@ -1905,24 +1824,23 @@ solist_update_incremental (svr4_info *info, CORE_ADDR debug_base,
>  
>  	 We expect gdbserver to provide updates for the namespace that
>  	 contains LM, which would be this namespace...  */
> -      so_list *sos = nullptr;
> -      if (library_list.solib_lists.find (debug_base)
> -	  != library_list.solib_lists.end ())
> -	std::swap (sos, library_list.solib_lists[debug_base]);
> -      if (sos == nullptr)
> +      std::vector<svr4_so> sos;
> +      auto it_debug_base = library_list.solib_lists.find (debug_base);
> +      if (it_debug_base != library_list.solib_lists.end ())
> +	std::swap (sos, it_debug_base->second);
> +      else
>  	{
>  	  /* ...or for the special zero namespace for earlier versions...  */
> -	  if (library_list.solib_lists.find (0)
> -	      != library_list.solib_lists.end ())
> -	    std::swap (sos, library_list.solib_lists[0]);
> +	  auto it_0 = library_list.solib_lists.find (0);
> +	  if (it_0 != library_list.solib_lists.end ())
> +	    std::swap (sos, it_0->second);
>  	}
>  
>        /* ...but nothing else.  */
> -      for (const std::pair<CORE_ADDR, so_list *> tuple
> -	     : library_list.solib_lists)
> -	gdb_assert (tuple.second == nullptr);
> +      for (const auto &tuple : library_list.solib_lists)
> +	gdb_assert (tuple.second.empty ());
>  
> -      *pnext = sos;
> +      std::move (sos.begin (), sos.end (), std::back_inserter (solist));
>      }
>    else
>      {
> @@ -1930,7 +1848,7 @@ solist_update_incremental (svr4_info *info, CORE_ADDR debug_base,
>  	 above check and deferral to solist_update_full ensures
>  	 that this call to svr4_read_so_list will never see the
>  	 first element.  */
> -      if (!svr4_read_so_list (info, lm, prev_lm, &pnext, 0))
> +      if (!svr4_read_so_list (info, lm, prev_lm, solist, 0))
>  	return 0;
>      }
>  
> @@ -1948,7 +1866,7 @@ disable_probes_interface (svr4_info *info)
>  	     "Reverting to original interface."));
>  
>    free_probes_table (info);
> -  free_solib_lists (info);
> +  info->solib_lists.clear ();
>  }
>  
>  /* Update the solib list as appropriate when using the
> @@ -3145,7 +3063,7 @@ svr4_solib_create_inferior_hook (int from_tty)
>  
>    /* Clear the probes-based interface's state.  */
>    free_probes_table (info);
> -  free_solib_lists (info);
> +  info->solib_lists.clear ();
>  
>    /* Relocate the main executable if necessary.  */
>    svr4_relocate_main_executable ();
> @@ -3373,14 +3291,17 @@ find_debug_base_for_solib (so_list *solib)
>  
>    svr4_info *info = get_svr4_info (current_program_space);
>    gdb_assert (info != nullptr);
> -  for (const std::pair<CORE_ADDR, so_list *> tuple
> -	 : info->solib_lists)
> +
> +  const lm_info_svr4 *lm_info = (const lm_info_svr4 *) solib->lm_info;
> +
> +  for (const auto &tuple : info->solib_lists)
>      {
>        CORE_ADDR debug_base = tuple.first;
> -      so_list *solist = tuple.second;
> +      const std::vector<svr4_so> &sos = tuple.second;
>  
> -      for (; solist != nullptr; solist = solist->next)
> -	if (svr4_same (*solib, *solist))
> +      for (const svr4_so &so : sos)
> +	if (svr4_same (solib->so_original_name, so.name.c_str (),
> +		       *lm_info, *so.lm_info))
>  	  return debug_base;
>      }
>  
> diff --git a/gdb/solib-svr4.h b/gdb/solib-svr4.h
> index 1aff3b59da8c..7cb6cabb109f 100644
> --- a/gdb/solib-svr4.h
> +++ b/gdb/solib-svr4.h
> @@ -48,6 +48,8 @@ struct lm_info_svr4 final : public lm_info
>    CORE_ADDR l_ld = 0, l_next = 0, l_prev = 0, l_name = 0;
>  };
>  
> +using lm_info_svr4_up = std::unique_ptr<lm_info_svr4>;
> +
>  /* Critical offsets and sizes which describe struct r_debug and
>     struct link_map on SVR4-like targets.  All offsets and sizes are
>     in bytes unless otherwise specified.  */
> -- 
> 2.42.0
>