Re: dlclose()

[Chris Blizzard <blizzard at redhat dot com>]

Jim Kingdon wrote:
> 
> Here's another patch for the dlclose() problem we've been talking
> about (5130 in bugzilla.redhat.com and all).  I'm not sure how well I
> like this patch but it should avoid the problem with flushing and
> reloading shared library symbols all the time as in the HJ/Sam patch.
> 
> Chris, want to weigh in on this (e.g. try out the patches)?  Mozilla
> is going to be one of the most affected if we do something dumb (or
> something great) with shared library support.
> 

Well, it doesn't seem any worse.  :)

--Chris

> 2000-02-16  Jim Kingdon  <kingdon@redhat.com>
> 
>         * solib.c (find_solib): New argument recheck.
>         * solib.c (solib_add): Pass it as 1, and add logic to delete
>         shared libraries which aren't still in the inferior.
>         (struct so_list): New field found_me, for solib_add.
>         * solib.c (other find_solib callers): Pass recheck as 0.
> 
> Index: solib.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/solib.c,v
> retrieving revision 1.1.1.10
> diff -u -r1.1.1.10 solib.c
> --- solib.c     1999/11/17 02:30:28     1.1.1.10
> +++ solib.c     2000/02/16 19:43:12
> @@ -31,6 +31,7 @@
>  #include "gdb_string.h"
>  #include <sys/param.h>
>  #include <fcntl.h>
> +#include <assert.h>
> 
>  #ifndef SVR4_SHARED_LIBS
>   /* SunOS shared libs need the nlist structure.  */
> @@ -143,6 +144,11 @@
>      char so_name[MAX_PATH_SIZE];       /* shared object lib name (FIXME) */
>      char symbols_loaded;       /* flag: symbols read in yet? */
>      char from_tty;             /* flag: print msgs? */
> +
> +    /* Flag for use within solib_add: have we seen this library actually
> +       still mapped in the inferior this pass?  */
> +    char found_me;
> +
>      struct objfile *objfile;   /* objfile for loaded lib */
>      struct section_table *sections;
>      struct section_table *sections_end;
> @@ -181,8 +187,7 @@
> 
>  static int symbol_add_stub PARAMS ((PTR));
> 
> -static struct so_list *
> -  find_solib PARAMS ((struct so_list *));
> +static struct so_list *find_solib (struct so_list *, int);
> 
>  static struct link_map *
>    first_link_map_member PARAMS ((void));
> @@ -975,8 +980,10 @@
>   */
> 
>  static struct so_list *
> -find_solib (so_list_ptr)
> -     struct so_list *so_list_ptr;      /* Last lm or NULL for first one */
> +find_solib (struct so_list *so_list_ptr,
> +           /* Nonzero if we should read all the entries from the inferior,
> +              not just the ones at the end of the list.  */
> +           int recheck)
>  {
>    struct so_list *so_list_next = NULL;
>    struct link_map *lm = NULL;
> @@ -985,7 +992,9 @@
>    if (so_list_ptr == NULL)
>      {
>        /* We are setting up for a new scan through the loaded images. */
> -      if ((so_list_next = so_list_head) == NULL)
> +      so_list_next = so_list_head;
> +      if (so_list_next == NULL
> +         || recheck)
>         {
>           /* We have not already read in the dynamic linking structures
>              from the inferior, lookup the address of the base structure. */
> @@ -1002,7 +1011,8 @@
>      {
>        /* We have been called before, and are in the process of walking
>           the shared library list.  Advance to the next shared object. */
> -      if ((lm = LM_NEXT (so_list_ptr)) == NULL)
> +      lm = LM_NEXT (so_list_ptr);
> +      if (recheck || lm == NULL)
>         {
>           /* We have hit the end of the list, so check to see if any were
>              added, but be quiet if we can't read from the target any more. */
> @@ -1020,7 +1030,7 @@
>         }
>        so_list_next = so_list_ptr->next;
>      }
> -  if ((so_list_next == NULL) && (lm != NULL))
> +  if ((so_list_next == NULL || recheck) && (lm != NULL))
>      {
>        /* Get next link map structure from inferior image and build a local
>           abbreviated load_map structure */
> @@ -1188,7 +1198,7 @@
>        /* Count how many new section_table entries there are.  */
>        so = NULL;
>        count = 0;
> -      while ((so = find_solib (so)) != NULL)
> +      while ((so = find_solib (so, 0)) != NULL)
>         {
>           if (so->so_name[0] && !match_main (so->so_name))
>             {
> @@ -1201,7 +1211,7 @@
> 
>           /* Add these section table entries to the target's table.  */
>           old = target_resize_to_sections (target, count);
> -         while ((so = find_solib (so)) != NULL)
> +         while ((so = find_solib (so, 0)) != NULL)
>             {
>               if (so->so_name[0])
>                 {
> @@ -1215,9 +1225,13 @@
>         }
>      }
> 
> +  for (so = so_list_head; so != NULL; so = so->next)
> +    so->found_me = 0;
> +
>    /* Now add the symbol files.  */
> -  while ((so = find_solib (so)) != NULL)
> +  while ((so = find_solib (so, 1)) != NULL)
>      {
> +      so->found_me = 1;
>        if (so->so_name[0] && re_exec (so->so_name) &&
>           !match_main (so->so_name))
>         {
> @@ -1240,6 +1254,37 @@
>         }
>      }
> 
> +  {
> +    struct so_list *prev;
> +    prev = NULL;
> +    for (so = so_list_head; so != NULL; so = so->next)
> +      {
> +       if (!so->found_me)
> +         {
> +           free_objfile (so->objfile);
> +
> +           /* FIXME: also need to fix up section tables that
> +              we put in the target vector, right?  */
> +           if (so_list_head->sections)
> +             {
> +               free ((PTR) so_list_head->sections);
> +             }
> +
> +           assert (so->abfd != NULL);
> +           if (!bfd_close (so->abfd))
> +             warning ("cannot close \"%s\": %s",
> +                      so->so_name, bfd_errmsg (bfd_get_error ()));
> +           if (prev == NULL)
> +             so_list_head = so->next;
> +           else
> +             prev->next = so->next;
> +
> +           free (so);
> +         }
> +       prev = so;
> +      }
> +  }
> +
>    /* Getting new symbols may change our opinion about what is
>       frameless.  */
>    if (so_last)
> @@ -1289,7 +1334,7 @@
>    addr_fmt = "016l";
>  #endif
> 
> -  while ((so = find_solib (so)) != NULL)
> +  while ((so = find_solib (so, 0)) != NULL)
>      {
>        if (so->so_name[0])
>         {
> @@ -1347,7 +1392,7 @@
>  {
>    register struct so_list *so = 0;     /* link map state variable */
> 
> -  while ((so = find_solib (so)) != NULL)
> +  while ((so = find_solib (so, 0)) != NULL)
>      {
>        if (so->so_name[0])
>         {

-- 
------------
Christopher Blizzard
http://people.redhat.com/blizzard/
A few years back, I saw a young child stuck in a tree.  Nowadays,
when I find myself in a troubling situation, I look back and wonder
if that kid saw me take that chocolate bar from his backpack on
the ground.
------------