Re: [ros-dev] [ros-diffs] [greatlrd] 22195: make malloc, calloc and some other function return NULL if size is 0
3 Jun
2006
3 Jun
'06
1:58 p.m.
greatlrd(a)svn.reactos.org wrote:
@@ -52,6 +55,9 @@
*/
void* calloc(size_t _nmemb, size_t _size)
{
+ if ( _size == 0)
+ return NULL;
+
return HeapAlloc(hHeap, HEAP_ZERO_MEMORY, ROUND_SIZE(_nmemb*_size) );
}
What if _nmemb is zero?
@@ -60,6 +66,9 @@
*/
void* realloc(void* _ptr, size_t _size)
{
+ if ( _size == 0)
+ return NULL;
+
if (!_ptr) return malloc(_size);
if (_size) return HeapReAlloc(hHeap, 0, _ptr, ROUND_SIZE(_size));
free(_ptr);
@@ -71,6 +80,9 @@
*/
umm... shouldn't we call free() if we're going to return NULL because
size is 0?
Also, the free() at the bottom is never called now.
void* _expand(void* _ptr, size_t _size)
{
+ if ( _size == 0)
+ return NULL;
+
return HeapReAlloc(hHeap, HEAP_REALLOC_IN_PLACE_ONLY, _ptr, ROUND_SIZE(_size));
}
Again, shouldn't we free the existing buffer if we're returning NULL
because size is 0?
3 Jun
3 Jun
2:39 p.m.
New subject: [ros-diffs] [greatlrd] 22195: make malloc, calloc and some other function return NULL if size is 0
Royce Mitchell III wrote:
realloc never frees the memory if it fails.
no, same as with realloc.
- Thomas
@@ -60,6 +66,9
@@
*/
void* realloc(void* _ptr, size_t _size)
{
+ if ( _size == 0)
+ return NULL;
+
if (!_ptr) return malloc(_size);
if (_size) return HeapReAlloc(hHeap, 0, _ptr, ROUND_SIZE(_size));
free(_ptr);
@@ -71,6 +80,9 @@
*/
umm... shouldn't we call free() if we're going to return NULL because
size is 0? Also, the free() at the bottom is never called now.
it's wrong and shouldn't even be there ;)
void*
_expand(void* _ptr, size_t _size)
{
+ if ( _size == 0)
+ return NULL;
+
return HeapReAlloc(hHeap, HEAP_REALLOC_IN_PLACE_ONLY, _ptr, ROUND_SIZE(_size));
}
Again, shouldn't we free the existing buffer if we're returning NULL
because size is 0? 
3:25 p.m.
New subject: [ros-diffs] [greatlrd] 22195: make malloc, calloc and some other function return NULL if size is 0
Maybe we should add free to realloc and expand
to avoid memmory leak ??
I know realloc fail in windows it can create memory leak
text from internet how malloc should work
" If the size of the space requested is 0, the behavior is
implementation-defined:
the value returned shall be either a null pointer or a unique pointer."
But most devloper assume malloc will return NULL if size is 0
But some windows platfroms it return vaild pointer.
The question is how should we handle it in reactos,
return NULL or vaild pointer for this case ?
----- Original Message -----
From: "Thomas Weidenmueller" <w3seek(a)reactos.com>
To: "ReactOS Development List" <ros-dev(a)reactos.org>
Sent: Saturday, June 03, 2006 4:39 PM
Subject: Re: [ros-dev] [ros-diffs] [greatlrd] 22195: make malloc, calloc and
some other function return NULL if size is 0
no, same as with realloc.
- Thomas
_______________________________________________
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Ros-dev(a)reactos.org
http://www.reactos.org/mailman/listinfo/ros-dev
Royce Mitchell III wrote:
realloc never frees the memory if it fails.
ROUND_SIZE(_size));
@@ -60,6
+66,9 @@
*/
void* realloc(void* _ptr, size_t _size)
{
+ if ( _size == 0)
+ return NULL;
+
if (!_ptr) return malloc(_size);
if (_size) return HeapReAlloc(hHeap, 0, _ptr, ROUND_SIZE(_size));
free(_ptr);
@@ -71,6 +80,9 @@
*/
umm... shouldn't we call free() if we're going to return NULL because
size is 0? Also, the free() at the bottom is never called
now.
it's wrong and shouldn't even be there ;)
>> void* _expand(void* _ptr, size_t _size)
>> {
>> + if ( _size == 0)
>> + return NULL;
>> +
>> return HeapReAlloc(hHeap, HEAP_REALLOC_IN_PLACE_ONLY, _ptr,
}
Again, shouldn't we free the existing buffer if we're returning NULL
because size is 0? 
4:16 p.m.
New subject: [ros-diffs] [greatlrd] 22195: make malloc, calloc and some other function return NULL if size is 0
Was the changes made to fix something? If not: don't fix whats not broken.
MSDN: The return value is NULL if the size is zero and the buffer
argument is not NULL, or if there is not enough available memory to
expand the block to the given size. In the first case, the original
block is freed. In the second, the original block is unchanged.
Magnus Olsen wrote:
Maybe we should add free to realloc and expand
to avoid memmory leak ??
NO!!!!!!!!!!!!! MSDN says the memory will not be freed if the call
fails, so the caller is free to continue to use the memory for whatever
he likes.
I know realloc fail in windows it can create memory leak
MSDN: The return value is NULL if the size is zero and the buffer
argument is not NULL, or if there is not enough available memory to
expand the block to the given size. In the first case, the original
block is freed. In the second, the original block is unchanged.
So, if realloc fails in windows it WILL ALWAYS create a memory leak
(unless you free the memory urself offcourse:-)
text from internet how malloc should work
With Internet do you mean MSDN? Every implementation of malloc behave
different. We only want it to behave like the Windows version...
" If the size of the space requested is 0, the behavior is
implementation-defined:
the value returned shall be either a null pointer or a unique pointer."
MSDN: If size is 0, malloc allocates a zero-length item in the heap and
returns a valid pointer to that item.
But most devloper assume malloc will return NULL if size is 0
But some windows platfroms it return vaild pointer.
The question is how should we handle it in reactos,
return NULL or vaild pointer for this case ?
Don't try to be smart, just do it like it says on MSDN.
BTW: The original code looks correct to me.
----- Original Message -----
From: "Thomas Weidenmueller" <w3seek(a)reactos.com>
To: "ReactOS Development List" <ros-dev(a)reactos.org>
Sent: Saturday, June 03, 2006 4:39 PM
Subject: Re: [ros-dev] [ros-diffs] [greatlrd] 22195: make malloc, calloc and
some other function return NULL if size is 0
no, same as with realloc.
- Thomas
_______________________________________________
Ros-dev mailing list
Ros-dev(a)reactos.org
http://www.reactos.org/mailman/listinfo/ros-dev
_______________________________________________
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Ros-dev(a)reactos.org
http://www.reactos.org/mailman/listinfo/ros-dev
Royce Mitchell III wrote:
realloc never frees the memory if it fails.
ROUND_SIZE(_size));
@@ -60,6
+66,9 @@
*/
void* realloc(void* _ptr, size_t _size)
{
+ if ( _size == 0)
+ return NULL;
+
if (!_ptr) return malloc(_size);
if (_size) return HeapReAlloc(hHeap, 0, _ptr, ROUND_SIZE(_size));
free(_ptr);
@@ -71,6 +80,9 @@
*/
umm... shouldn't we call free() if we're going to return NULL because
size is 0? Also, the free() at the bottom is never called
now.
it's wrong and shouldn't even be there ;)
>> void* _expand(void* _ptr, size_t _size)
>> {
>> + if ( _size == 0)
>> + return NULL;
>> +
>> return HeapReAlloc(hHeap, HEAP_REALLOC_IN_PLACE_ONLY, _ptr, }
Again, shouldn't we free the existing buffer if we're returning NULL
because size is 0?
4:37 p.m.
New subject: [ros-diffs] [greatlrd] 22195: make malloc, calloc and some other function return NULL if size is 0
HI
Malloc(0) did not reaturn NULL;
that was the fix for. I am reading the IEEE spec
how malloc should work, and it exists two diffent
implement of it. and some exprenet on diffent windows
platfrom show diffent behvior about malloc(0)
----- Original Message -----
From: "Gunnar Dalsnes" <hardon(a)online.no>
To: "ReactOS Development List" <ros-dev(a)reactos.org>
Sent: Saturday, June 03, 2006 6:16 PM
Subject: Re: [ros-dev] [ros-diffs] [greatlrd] 22195: make malloc,calloc and
some other function return NULL if size is 0
MSDN: If size is 0, malloc allocates a zero-length item in the heap and
returns a valid pointer to that item.
> But most devloper assume malloc will
return NULL if size is 0
> But some windows platfroms it return vaild pointer.
> The question is how should we handle
it in reactos,
> return NULL or vaild pointer for this case ?
Don't try to be smart, just do it like it says on MSDN.
BTW: The original code looks correct to me.
> ----- Original Message -----
> From: "Thomas Weidenmueller" <w3seek(a)reactos.com>
> To: "ReactOS Development List" <ros-dev(a)reactos.org>
> Sent: Saturday, June 03, 2006 4:39 PM
> Subject: Re: [ros-dev] [ros-diffs] [greatlrd] 22195: make malloc, calloc and
Was the changes made to fix something? If not:
don't fix whats not broken.
MSDN: The return value is NULL if the size is zero and the buffer
argument is not NULL, or if there is not enough available memory to
expand the block to the given size. In the first case, the original
block is freed. In the second, the original block is unchanged.
Magnus Olsen wrote:
pointer."
Maybe we should add free to realloc and expand
to avoid memmory leak ??
NO!!!!!!!!!!!!! MSDN says the memory will not be freed if the call
fails, so the caller is free to continue to use the memory for whatever
he likes.
I know realloc fail in windows it can create memory leak
MSDN: The return value is NULL if the size is zero and the buffer
argument is not NULL, or if there is not enough available memory to
expand the block to the given size. In the first case, the original
block is freed. In the second, the original block is unchanged.
So, if realloc fails in windows it WILL ALWAYS create a memory leak
(unless you free the memory urself offcourse:-)
text from internet how malloc should work
With Internet do you mean MSDN? Every implementation of malloc behave
different. We only want it to behave like the Windows version...
>
> " If the size of the space requested is 0, the behavior is
> implementation-defined:
> the value returned shall be either a null pointer or a unique
some other
function return NULL if size is 0
_______________________________________________
Ros-dev mailing list
Ros-dev(a)reactos.org
http://www.reactos.org/mailman/listinfo/ros-dev
_______________________________________________
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Ros-dev(a)reactos.org
http://www.reactos.org/mailman/listinfo/ros-dev Royce Mitchell III wrote:
ROUND_SIZE(_size));
> @@ -60,6 +66,9 @@
> */
> void* realloc(void* _ptr, size_t _size)
> {
> + if ( _size == 0)
> + return NULL;
> +
> if (!_ptr) return malloc(_size);
> if (_size) return HeapReAlloc(hHeap, 0, _ptr, ROUND_SIZE(_size));
> free(_ptr);
> @@ -71,6 +80,9 @@
> */
>
>
umm... shouldn't we call free() if we're going to return NULL because
size is 0?
realloc never frees the memory if it fails.
Also, the free() at the bottom is never called
now.
it's wrong and shouldn't even be there ;)
>> void* _expand(void* _ptr, size_t _size)
>> {
>> + if ( _size == 0)
>> + return NULL;
>> +
>> return HeapReAlloc(hHeap, HEAP_REALLOC_IN_PLACE_ONLY, _ptr, > }
>
>
Again, shouldn't we free the existing buffer if we're returning NULL
because size is 0?
no, same as with realloc.
- Thomas
_______________________________________________
Ros-dev mailing list
Ros-dev(a)reactos.org
http://www.reactos.org/mailman/listinfo/ros-dev
4:57 p.m.
New subject: [ros-diffs] [greatlrd] 22195: make malloc, calloc and some other function return NULL if size is 0
Magnus Olsen wrote:
HI
Malloc(0) did not reaturn NULL;
that was the fix for. I am reading the IEEE spec
how malloc should work, and it exists two diffent
implement of it. and some exprenet on diffent windows
platfrom show diffent behvior about malloc(0)
IEEE specs really have nothing to do with how Windows behaves. Windows
NEVER follow standards. A quick test on Win XP shows malloc(0) return a
pointer to stack, so MSDN is right (surprise!) and your fix is wrong. If
some older version of Windows did otherwise, this is a job for a
compability framework (which we dont have).
5:10 p.m.
New subject: [ros-diffs] [greatlrd] 22195: make malloc, calloc and some other function return NULL if size is 0
Gunnar Dalsnes wrote:
Magnus Olsen wrote:
Wow!
what a cheesy way to get the stack pointer.
James
HI
Malloc(0) did not reaturn NULL;
that was the fix for. I am reading the IEEE spec
how malloc should work, and it exists two diffent
implement of it. and some exprenet on diffent windows
platfrom show diffent behvior about malloc(0)
IEEE specs really have nothing to do with how Windows behaves. Windows
NEVER follow standards. A quick test on Win XP shows malloc(0) return a
pointer to stack, so MSDN is right (surprise!) and your fix is wrong. If
some older version of Windows did otherwise, this is a job for a
compability framework (which we dont have).
5:16 p.m.
New subject: [ros-diffs] [greatlrd] 22195: make malloc, calloc and some other function return NULL if size is 0
I talk with filip about it, he confrim the fix is correct
IEEE spec did mentor it exists two diffent behvoir
on malloc(0). My windows 2000 is return NULL from
malloc(0) and some other windows I got did not.
----- Original Message -----
From: "Gunnar Dalsnes" <hardon(a)online.no>
To: "ReactOS Development List" <ros-dev(a)reactos.org>
Sent: Saturday, June 03, 2006 6:57 PM
Subject: Re: [ros-dev] [ros-diffs] [greatlrd] 22195: make malloc,calloc and
some other function return NULL if size is 0
Magnus Olsen wrote:
HI
Malloc(0) did not reaturn NULL;
that was the fix for. I am reading the IEEE spec
how malloc should work, and it exists two diffent
implement of it. and some exprenet on diffent windows
platfrom show diffent behvior about malloc(0)
IEEE specs really have nothing to do with how Windows behaves. Windows
NEVER follow standards. A quick test on Win XP shows malloc(0) return a
pointer to stack, so MSDN is right (surprise!) and your fix is wrong. If
some older version of Windows did otherwise, this is a job for a
compability framework (which we dont have).
_______________________________________________
Ros-dev mailing list
Ros-dev(a)reactos.org
http://www.reactos.org/mailman/listinfo/ros-dev 
3 Jun
3 Jun
10:37 p.m.
New subject: [ros-diffs] [greatlrd] 22195: make malloc, calloc and some other function return NULL if size is 0
On Saturday 03 June 2006 14:39, Thomas Weidenmueller wrote:
no, same as with realloc.
This call isn't in Posix or any C library I've ever used, but seems to be
correct. Expanding a buffer by 0 bytes, if called from userspace, should
return the original buffer. Called internally, like this appears to be,
returning NULL indicates the buffer wasn't touched.
DRH
(If you need help with how people will *expect* known functions to work
(specifically C library functions) just ask :)
Royce Mitchell III wrote:
realloc never frees the memory if it fails.
Calling realloc() sith size as 0 is supposed to free the buffer, not fail.
Heres how realloc() is defined in the man-page:
realloc() changes the size of the memory block pointed to by ptr to
size bytes. The contents will be unchanged to the minimum of the old
and new sizes; newly allocated memory will be uninitialized. If ptr is
NULL, the call is equivalent to malloc(size); if size is equal to zero,
the call is equivalent to free(ptr). Unless ptr is NULL, it must have
been returned by an earlier call to malloc(), calloc() or realloc().
If the area pointed to was moved, a free(ptr) is done.
@@ -60,6
+66,9 @@
*/
void* realloc(void* _ptr, size_t _size)
{
+ if ( _size == 0)
+ return NULL;
+
if (!_ptr) return malloc(_size);
if (_size) return HeapReAlloc(hHeap, 0, _ptr, ROUND_SIZE(_size));
free(_ptr);
@@ -71,6 +80,9 @@
*/
umm... shouldn't we call free() if we're going to return NULL because
size is 0? void* _expand(void* _ptr, size_t _size)
{
+ if ( _size == 0)
+ return NULL;
+
return HeapReAlloc(hHeap, HEAP_REALLOC_IN_PLACE_ONLY, _ptr,
ROUND_SIZE(_size)); }
Again, shouldn't we free the existing buffer if we're returning NULL
because size is 0?
10:44 p.m.
New subject: [ros-diffs] [greatlrd] 22195: make malloc, calloc and some other function return NULL if size is 0
Sorry about that last post. I forgot that MS never follows published
specifications. The ANSI C standard states that malloc() of any memory should
either allocate the memory or fail - most implementations of the standard C
library return NULL on a call to malloc with 0 as the size.
Calls to realloc() with size as 0 are supposed to free the pointer.
However, MS doesn't follow ANSI at all, anywhere, and since ReactOS is meant
to be 100% binary compatable with Windows it should follow the MSDN specs for
functions.
DRH
4 Jun
4 Jun
8:45 a.m.
New subject: [ros-diffs] [greatlrd] 22195: make malloc, calloc and some other function return NULL if size is 0
I always thought that Microsoft's malloc() returned a fully valid heap
pointer when you pass a size of zero. Such a pointer would be a valid heap
pointer of zero size (consisting only of a heap linked list entry "before"
the pointer), and could be freed with free().
realloc() does free() and returns NULL if _size is zero. This is even true
if you originally passed zero to malloc() and got an empty heap pointer. In
this way, realloc is inconsistent with malloc(), but that's the way it is.
Melissa
----- Original Message -----
From: "D. Hazelton" <dhazelton(a)enter.net>
To: <ros-dev(a)reactos.org>
Sent: Saturday, June 03, 2006 15:44
Subject: Re: [ros-dev] [ros-diffs] [greatlrd] 22195: make malloc,calloc and
some other function return NULL if size is 0
Sorry about that last post. I forgot that MS never
follows published
specifications. The ANSI C standard states that malloc() of any memory
should
either allocate the memory or fail - most implementations of the standard
C
library return NULL on a call to malloc with 0 as the size.
Calls to realloc() with size as 0 are supposed to free the pointer.
However, MS doesn't follow ANSI at all, anywhere, and since ReactOS is
meant
to be 100% binary compatable with Windows it should follow the MSDN specs
for
functions.
DRH
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http://www.reactos.org/mailman/listinfo/ros-dev
6682
days inactive
6683
days old
11 comments
7 participants
participants (7)
-
D. Hazelton -
Gunnar Dalsnes -
James Tabor -
Magnus Olsen -
Myria -
Royce Mitchell III -
Thomas Weidenmueller