On Mon, 2005-05-16 at 15:20 +0200, Jim Meyering wrote:
> Yoann Vandoorselaere <[EMAIL PROTECTED]> wrote:
> > This patch fix constness warning in the GnuLib hash module.
>
> I'm all for avoiding warnings, but not when it detracts from what I
> think of as the correctness of an interface, as it would in this case.
>
> Those `const void *entry' parameters constitute a promise
> by the hash module that it will not try to write through
> those pointers. Removing `const' here might make users of
> these functions wonder whether the functions write through
> the void pointers.
Since the interface let the user provide a function for deleting data
(which thus does not use const), you might then as well workaround this
issue using:
union {
const void *val_ro;
void *val_rw;
} user_data;
And use the later in order to provide the deletion callback with a not
const pointer.
Proof of concept patch attached.
--
Yoann Vandoorselaere | Responsable R&D / CTO | PreludeIDS Technologies
Tel: +33 (0)8 70 70 21 58 Fax: +33(0)4 78 42 21 58
http://www.prelude-ids.com
Index: lib/hash.c
===================================================================
RCS file: /cvsroot/gnulib/gnulib/lib/hash.c,v
retrieving revision 1.38
diff -u -r1.38 hash.c
--- lib/hash.c 14 May 2005 06:03:58 -0000 1.38
+++ lib/hash.c 16 May 2005 13:41:52 -0000
@@ -178,7 +178,7 @@
for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
{
- if (bucket->data)
+ if (bucket->user_data.ro_data)
{
struct hash_entry const *cursor = bucket;
size_t bucket_length = 1;
@@ -206,7 +206,7 @@
for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
{
- if (bucket->data)
+ if (bucket->user_data.ro_data)
{
struct hash_entry const *cursor = bucket;
@@ -256,12 +256,12 @@
if (! (bucket < table->bucket_limit))
abort ();
- if (bucket->data == NULL)
+ if (bucket->user_data.ro_data == NULL)
return NULL;
for (cursor = bucket; cursor; cursor = cursor->next)
- if (table->comparator (entry, cursor->data))
- return cursor->data;
+ if (table->comparator (entry, cursor->user_data.ro_data))
+ return cursor->user_data.rw_data;
return NULL;
}
@@ -286,8 +286,8 @@
for (bucket = table->bucket; ; bucket++)
if (! (bucket < table->bucket_limit))
abort ();
- else if (bucket->data)
- return bucket->data;
+ else if (bucket->user_data.ro_data)
+ return bucket->user_data.rw_data;
}
/* Return the user data for the entry following ENTRY, where ENTRY has been
@@ -306,13 +306,13 @@
/* Find next entry in the same bucket. */
for (cursor = bucket; cursor; cursor = cursor->next)
- if (cursor->data == entry && cursor->next)
- return cursor->next->data;
+ if (cursor->user_data.ro_data == entry && cursor->next)
+ return cursor->next->user_data.rw_data;
/* Find first entry in any subsequent bucket. */
while (++bucket < table->bucket_limit)
- if (bucket->data)
- return bucket->data;
+ if (bucket->user_data.ro_data)
+ return bucket->user_data.rw_data;
/* None found. */
return NULL;
@@ -332,13 +332,13 @@
for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
{
- if (bucket->data)
+ if (bucket->user_data.ro_data)
{
for (cursor = bucket; cursor; cursor = cursor->next)
{
if (counter >= buffer_size)
return counter;
- buffer[counter++] = cursor->data;
+ buffer[counter++] = cursor->user_data.rw_data;
}
}
}
@@ -364,11 +364,11 @@
for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
{
- if (bucket->data)
+ if (bucket->user_data.ro_data)
{
for (cursor = bucket; cursor; cursor = cursor->next)
{
- if (!(*processor) (cursor->data, processor_data))
+ if (!(*processor) (cursor->user_data.rw_data, processor_data))
return counter;
counter++;
}
@@ -608,7 +608,7 @@
for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
{
- if (bucket->data)
+ if (bucket->user_data.ro_data)
{
struct hash_entry *cursor;
struct hash_entry *next;
@@ -617,8 +617,8 @@
for (cursor = bucket->next; cursor; cursor = next)
{
if (table->data_freer)
- (*table->data_freer) (cursor->data);
- cursor->data = NULL;
+ (*table->data_freer) (cursor->user_data.rw_data);
+ cursor->user_data.ro_data = NULL;
next = cursor->next;
/* Relinking is done one entry at a time, as it is to be expected
@@ -629,8 +629,8 @@
/* Free the bucket head. */
if (table->data_freer)
- (*table->data_freer) (bucket->data);
- bucket->data = NULL;
+ (*table->data_freer) (bucket->user_data.rw_data);
+ bucket->user_data.ro_data = NULL;
bucket->next = NULL;
}
}
@@ -656,11 +656,11 @@
{
for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
{
- if (bucket->data)
+ if (bucket->user_data.ro_data)
{
for (cursor = bucket; cursor; cursor = cursor->next)
{
- (*table->data_freer) (cursor->data);
+ (*table->data_freer) (cursor->user_data.rw_data);
}
}
}
@@ -729,7 +729,7 @@
static void
free_entry (Hash_table *table, struct hash_entry *entry)
{
- entry->data = NULL;
+ entry->user_data.ro_data = NULL;
entry->next = table->free_entry_list;
table->free_entry_list = entry;
}
@@ -754,13 +754,13 @@
*bucket_head = bucket;
/* Test for empty bucket. */
- if (bucket->data == NULL)
+ if (bucket->user_data.ro_data == NULL)
return NULL;
/* See if the entry is the first in the bucket. */
- if ((*table->comparator) (entry, bucket->data))
+ if ((*table->comparator) (entry, bucket->user_data.ro_data))
{
- void *data = bucket->data;
+ void *data = bucket->user_data.rw_data;
if (delete)
{
@@ -775,7 +775,7 @@
}
else
{
- bucket->data = NULL;
+ bucket->user_data.ro_data = NULL;
}
}
@@ -785,9 +785,9 @@
/* Scan the bucket overflow. */
for (cursor = bucket; cursor->next; cursor = cursor->next)
{
- if ((*table->comparator) (entry, cursor->next->data))
+ if ((*table->comparator) (entry, cursor->next->user_data.ro_data))
{
- void *data = cursor->next->data;
+ void *data = cursor->next->user_data.rw_data;
if (delete)
{
@@ -836,10 +836,10 @@
new_table->free_entry_list = table->free_entry_list;
for (bucket = table->bucket; bucket < table->bucket_limit; bucket++)
- if (bucket->data)
+ if (bucket->user_data.ro_data)
for (cursor = bucket; cursor; cursor = next)
{
- void *data = cursor->data;
+ void *data = cursor->user_data.rw_data;
struct hash_entry *new_bucket
= (new_table->bucket
+ new_table->hasher (data, new_table->n_buckets));
@@ -849,7 +849,7 @@
next = cursor->next;
- if (new_bucket->data)
+ if (new_bucket->user_data.ro_data)
{
if (cursor == bucket)
{
@@ -860,7 +860,7 @@
if (new_entry == NULL)
return false;
- new_entry->data = data;
+ new_entry->user_data.ro_data = data;
new_entry->next = new_bucket->next;
new_bucket->next = new_entry;
}
@@ -878,7 +878,7 @@
overflow into a bucket header. Also take care of the
simple case of moving from a bucket header into a bucket
header. */
- new_bucket->data = data;
+ new_bucket->user_data.ro_data = data;
new_table->n_buckets_used++;
if (cursor != bucket)
free_entry (new_table, cursor);
@@ -920,7 +920,7 @@
/* ENTRY is not matched, it should be inserted. */
- if (bucket->data)
+ if (bucket->user_data.ro_data)
{
struct hash_entry *new_entry = allocate_entry (table);
@@ -929,16 +929,16 @@
/* Add ENTRY in the overflow of the bucket. */
- new_entry->data = (void *) entry;
+ new_entry->user_data.ro_data = entry;
new_entry->next = bucket->next;
bucket->next = new_entry;
table->n_entries++;
- return (void *) entry;
+ return new_entry->user_data.rw_data;
}
/* Add ENTRY right in the bucket head. */
- bucket->data = (void *) entry;
+ bucket->user_data.ro_data = entry;
table->n_entries++;
table->n_buckets_used++;
@@ -990,7 +990,7 @@
return NULL;
table->n_entries--;
- if (!bucket->data)
+ if (!bucket->user_data.ro_data)
{
table->n_buckets_used--;
Index: lib/hash.h
===================================================================
RCS file: /cvsroot/gnulib/gnulib/lib/hash.h,v
retrieving revision 1.16
diff -u -r1.16 hash.h
--- lib/hash.h 14 May 2005 06:03:58 -0000 1.16
+++ lib/hash.h 16 May 2005 13:41:52 -0000
@@ -34,7 +34,12 @@
struct hash_entry
{
- void *data;
+ union
+ {
+ const void *ro_data;
+ void *rw_data;
+ } user_data;
+
struct hash_entry *next;
};
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