Using 'solib-search-path' on 64/32-bit targets

[Dmitry Antipov <dantipov at nvidia dot com>]

For the remote debugging on a 64-bit target with 32-bit compatibility, is it reasonable
to have gdb.setup with 'solib-search-path' pointed to both 64- and 32-bit libraries
(say, 'set solib-search-path /path/to/target/fs/lib64:/path/to/target/fs/lib32')? Currently GDB
just gives up the search if an inappropriate library is found, and will not try to examine
the rest of 'solib-search-path' entries. IOW if we're debugging 32-bit process with libXXX.so
dependency and 'solib-search-path' is set as above, /path/to/target/fs/lib32/libXXX.so won't
be found if /path/to/target/fs/lib64/libXXX.so is present. Attached is a simple attempt to
"fix" that behavior (toggled by new 'solib-search-giveup' flag), but I'm not sure whether
it needs to be "fixed" in that way at all :-).

Dmitry

diff --git a/gdb/solib.c b/gdb/solib.c
index 3dba5eaa8a..500f76c823 100644
--- a/gdb/solib.c
+++ b/gdb/solib.c
@@ -91,6 +91,16 @@ struct target_so_ops *current_target_so_ops;
 
 /* Local function prototypes */
 
+static int solib_search_giveup = 1;
+
+static void
+show_solib_search_giveup (struct ui_file *file, int from_tty,
+			  struct cmd_list_element *c, const char *value)
+{
+  fprintf_filtered (file, _("Giving up search after finding inappropriate "
+			    "library is %s.\n"), value);
+}
+
 /* If non-empty, this is a search path for loading non-absolute shared library
    symbol files.  This takes precedence over the environment variables PATH
    and LD_LIBRARY_PATH.  */
@@ -493,7 +503,7 @@ solib_bfd_fopen (char *pathname, int fd)
 /* Find shared library PATHNAME and open a BFD for it.  */
 
 gdb_bfd_ref_ptr
-solib_bfd_open (char *pathname)
+solib_bfd_open_1 (char *pathname)
 {
   char *found_pathname;
   int found_file;
@@ -516,20 +526,59 @@ solib_bfd_open (char *pathname)
 
   /* Check bfd format.  */
   if (!bfd_check_format (abfd.get (), bfd_object))
-    error (_("`%s': not in executable format: %s"),
-	   bfd_get_filename (abfd), bfd_errmsg (bfd_get_error ()));
+    {
+      if (solib_search_giveup)
+	error (_("`%s': not in executable format: %s"),
+	       bfd_get_filename (abfd), bfd_errmsg (bfd_get_error ()));
+      else
+	{
+	  warning (_("`%s': not in executable format: %s"),
+		   bfd_get_filename (abfd), bfd_errmsg (bfd_get_error ()));
+	  return NULL;
+	}
+    }
 
   /* Check bfd arch.  */
   b = gdbarch_bfd_arch_info (target_gdbarch ());
   if (!b->compatible (b, bfd_get_arch_info (abfd.get ())))
-    warning (_("`%s': Shared library architecture %s is not compatible "
-               "with target architecture %s."), bfd_get_filename (abfd),
-             bfd_get_arch_info (abfd.get ())->printable_name,
-	     b->printable_name);
+    {
+      warning (_("`%s': Shared library architecture %s is not compatible "
+		 "with target architecture %s."), bfd_get_filename (abfd),
+	       bfd_get_arch_info (abfd.get ())->printable_name,
+	       b->printable_name);
+      if (!solib_search_giveup)
+	return NULL;
+    }
 
   return abfd;
 }
 
+gdb_bfd_ref_ptr
+solib_bfd_open (char *pathname)
+{
+  if (solib_search_path && !solib_search_giveup)
+    {
+      /* Lookup PATHNAME in all solib_search_path entries until
+	 suitable solib is found.  */
+      gdb_bfd_ref_ptr abfd;
+      char *savedpath = solib_search_path;
+      char *p, *orig, *sopath = xstrdup (solib_search_path);
+      const char sep[] { DIRNAME_SEPARATOR, '\0' };
+
+      orig = sopath;
+      while ((p = strsep (&sopath, sep)))
+	{
+	  solib_search_path = p;
+	  if ((abfd = solib_bfd_open_1 (pathname)) != NULL)
+	    break;
+	}
+      solib_search_path = savedpath;
+      xfree (orig);
+      return abfd;
+    }
+  return solib_bfd_open_1 (pathname);
+}
+
 /* Given a pointer to one of the shared objects in our list of mapped
    objects, use the recorded name to open a bfd descriptor for the
    object, build a section table, relocate all the section addresses
@@ -1654,6 +1703,11 @@ For other (relative) files, you can add directories using\n\
   add_alias_cmd ("solib-absolute-prefix", "sysroot", class_support, 0,
 		 &showlist);
 
+  add_setshow_boolean_cmd ("solib-search-giveup", class_support,
+			   &solib_search_giveup, "DOCME", "DOCME", "DOCME",
+			   NULL, show_solib_search_giveup,
+			   &setlist, &showlist);
+
   add_setshow_optional_filename_cmd ("solib-search-path", class_support,
 				     &solib_search_path, _("\
 Set the search path for loading non-absolute shared library symbol files."),