Re: ls segfault - coreutils-6.5

[Jim Meyering]

Paul Eggert <address@hidden> wrote:
> Jim Meyering <address@hidden> writes:
>> FYI, I wanted to have my cake and eat it too, so was about to
>> check in the following change.  I'll merge things and make a
>> new coreutils release soon.
>
> Thanks, wow, that's quick work, and your patch is much nicer
> (obviously).  I briefly reviewed it and it's what I wished
> I would have written.

Thanks for the quick review!
Here's what I expect to check in to gnulib,
as soon as a few rounds of coreutils tests pass:

        * lib/idcache.c: Restore most of the 2006-11-06 patch, so as to
        continue using the flexible array member (thus, this module performs
        half as many malloc calls), with the addition that...
        (getgroup, getuser): Consistently record a non-match via an empty
        "name" string, and map an empty string match to a NULL return value.
        * modules/idcache (Depends-on): Re-add flexmember.

Index: lib/idcache.c
===================================================================
RCS file: /sources/gnulib/gnulib/lib/idcache.c,v
retrieving revision 1.21
diff -u -p -r1.21 idcache.c
--- lib/idcache.c       20 Nov 2006 09:30:52 -0000      1.21
+++ lib/idcache.c       20 Nov 2006 10:40:06 -0000
@@ -19,6 +19,7 @@

 #include <config.h>

+#include <stddef.h>
 #include <stdio.h>
 #include <string.h>
 #include <sys/types.h>
@@ -40,8 +41,8 @@ struct userid
       uid_t u;
       gid_t g;
     } id;
-  char *name;
   struct userid *next;
+  char name[FLEXIBLE_ARRAY_MEMBER];
 };

 static struct userid *user_alist;
@@ -55,21 +56,31 @@ char *
 getuser (uid_t uid)
 {
   struct userid *tail;
-  struct passwd *pwent;
+  struct userid *match = NULL;

   for (tail = user_alist; tail; tail = tail->next)
-    if (tail->id.u == uid)
-      return tail->name;
+    {
+      if (tail->id.u == uid)
+       {
+         match = tail;
+         break;
+       }
+    }

-  pwent = getpwuid (uid);
-  tail = xmalloc (sizeof *tail);
-  tail->id.u = uid;
-  tail->name = pwent ? xstrdup (pwent->pw_name) : NULL;
+  if (match == NULL)
+    {
+      struct passwd *pwent = getpwuid (uid);
+      char const *name = pwent ? pwent->pw_name : "";
+      match = xmalloc (offsetof (struct userid, name) + strlen (name) + 1);
+      match->id.u = uid;
+      strcpy (match->name, name);
+
+      /* Add to the head of the list, so most recently used is first.  */
+      match->next = user_alist;
+      user_alist = match;
+    }

-  /* Add to the head of the list, so most recently used is first.  */
-  tail->next = user_alist;
-  user_alist = tail;
-  return tail->name;
+  return match->name[0] ? match->name : NULL;
 }

 /* Translate USER to a UID, with cache.
@@ -104,8 +115,8 @@ getuidbyname (const char *user)
     }
 #endif

-  tail = xmalloc (sizeof *tail);
-  tail->name = xstrdup (user);
+  tail = xmalloc (offsetof (struct userid, name) + strlen (user) + 1);
+  strcpy (tail->name, user);

   /* Add to the head of the list, so most recently used is first.  */
   if (pwent)
@@ -131,21 +142,31 @@ char *
 getgroup (gid_t gid)
 {
   struct userid *tail;
-  struct group *grent;
+  struct userid *match = NULL;

   for (tail = group_alist; tail; tail = tail->next)
-    if (tail->id.g == gid)
-      return tail->name;
+    {
+      if (tail->id.g == gid)
+       {
+         match = tail;
+         break;
+       }
+    }

-  grent = getgrgid (gid);
-  tail = xmalloc (sizeof *tail);
-  tail->id.g = gid;
-  tail->name = grent ? xstrdup (grent->gr_name) : NULL;
+  if (match == NULL)
+    {
+      struct group *grent = getgrgid (gid);
+      char const *name = grent ? grent->gr_name : "";
+      match = xmalloc (offsetof (struct userid, name) + strlen (name) + 1);
+      match->id.g = gid;
+      strcpy (match->name, name);
+
+      /* Add to the head of the list, so most recently used is first.  */
+      match->next = group_alist;
+      group_alist = match;
+    }

-  /* Add to the head of the list, so most recently used is first.  */
-  tail->next = group_alist;
-  group_alist = tail;
-  return tail->name;
+  return match->name[0] ? match->name : NULL;
 }

 /* Translate GROUP to a GID, with cache.
@@ -172,7 +193,7 @@ getgidbyname (const char *group)
   grent = getgrnam (group);
 #ifdef __DJGPP__
   /* We need to pretend to belong to group GROUP, to make
-     grp functions know about any arbitrary group name.  */
+     grp functions know about an arbitrary group name.  */
   if (!grent && strspn (group, digits) < strlen (group))
     {
       setenv ("GROUP", group, 1);
@@ -180,8 +201,8 @@ getgidbyname (const char *group)
     }
 #endif

-  tail = xmalloc (sizeof *tail);
-  tail->name = xstrdup (group);
+  tail = xmalloc (offsetof (struct userid, name) + strlen (group) + 1);
+  strcpy (tail->name, group);

   /* Add to the head of the list, so most recently used is first.  */
   if (grent)
Index: modules/idcache
===================================================================
RCS file: /sources/gnulib/gnulib/modules/idcache,v
retrieving revision 1.9
diff -u -p -r1.9 idcache
--- modules/idcache     20 Nov 2006 09:10:18 -0000      1.9
+++ modules/idcache     20 Nov 2006 10:40:06 -0000
@@ -6,6 +6,7 @@ lib/idcache.c
 m4/idcache.m4

 Depends-on:
+flexmember
 xalloc

 configure.ac: