This is regarding to test an SDK memory stuff.
In what situation malloc gets fail.
any comment/reply pls....
regards
Jul 17 '07
34  13406 
In article <11************ **********@57g2 000hsv.googlegr oups.com>,
crox <cr*****@gmail. comwrote:
>it is really platform specific, for example in my system libc, malloc
has this implemetation:
...
/* why would you ever want a negative malloc, this would mean */
/* a very large positive number which can't be filled */
if ((int)nbytes < 0){
The argument to malloc() has type size_t, which is unsigned, so you
*can't* pass it a negative value. It may well be true that values
corresponding to negative ints are usually the result of a bug in the
program causing a negative value to be converted to a large size_t,
but I'm not sure why your code bothers to make this check, since if
requests for "very large" amounts of memory can't be filled, it will
fail anyway without the check.
I think the comment would be more accurate if it read "Why would you
ever want to malloc such a huge amount? It can't be done and is more
likely an erroneous attempt to malloc a negative size".
-- Richard
--
"Considerat ion shall be given to the need for as many as 32 characters
in some alphabets" - X3.4, 1963.
On Jul 24, 3:12 pm, Richard Heathfield <r...@see.sig.i nvalidwrote:
Ben Pfaff said:
Please, tell us how.
Sorry to be so vague about this. Will it suffice to say that I use a
wrapper?
How?
Assume that you have a program in which malloc is not wrappred.
How do you wrap it without going through and replacing all the calls
to
malloc? Sure
#define malloc wrap_malloc
will probably work, but you can't redefine a library function in
portable code.
(given that you have a wrapper function things are straightforward .
Store state as a global or pseudo-global (static in a module),
manipulate with wrap_malloc_cha nge_state()
then the wrapper function will return NULL (fail) or call
malloc, depending on the state)
- William Hughes
On Jul 25, 4:41 am, rich...@cogsci. ed.ac.uk (Richard Tobin) wrote:
In article <1185352068.681 434.313...@57g2 000hsv.googlegr oups.com>,
crox <craz...@gmail. comwrote:
it is really platform specific, for example in my system libc, malloc
has this implemetation:
...
/* why would you ever want a negative malloc, this would mean */
/* a very large positive number which can't be filled */
if ((int)nbytes < 0){
The argument to malloc() has type size_t, which is unsigned, so you
*can't* pass it a negative value. It may well be true that values
corresponding to negative ints are usually the result of a bug in the
program causing a negative value to be converted to a large size_t,
but I'm not sure why your code bothers to make this check, since if
requests for "very large" amounts of memory can't be filled, it will
fail anyway without the check.
I think the comment would be more accurate if it read "Why would you
ever want to malloc such a huge amount? It can't be done and is more
likely an erroneous attempt to malloc a negative size".
If the chip can address it, and if I have that much available, I would
be rather put out if the malloc() function arbitrarily decided not to
give it to me.
That little snippet of code is by a programmer trying to be more
clever than he ought to be.
IMO-YMMV.
On Jul 17, 6:36 am, "niranjan.si... @gmail.com"
<niranjan.si... @gmail.comwrote :
This is regarding to test an SDK memory stuff.
In what situation malloc gets fail.
any comment/reply pls....
regards
If you just wish to test your error paths, you don't really need to
make malloc fail, just make your program think that it did:
#if TESTING
/* function to determine if malloc should fail */
int malloc_should_f ail(void);
#define malloc(S) (malloc_should_ fail() ? NULL : (malloc)(S))
#endif
I don't believe it is portable to override malloc with a macro, but
its only for testing purposes, not your release builds.
In article <11************ **********@o61g 2000hsh.googleg roups.com>,
user923005 <dc*****@connx. comwrote:
>/* why would you ever want a negative malloc, this would mean */
/* a very large positive number which can't be filled */
>If the chip can address it, and if I have that much available, I would
be rather put out if the malloc() function arbitrarily decided not to
give it to me.
I assume from the comment that it isn't available. It's not unusual
for half the address space to be used for kernel memory. Of course,
if size_t is 64 bits, there's no prospect of more than half of it being
available anyway in the foreseeable future.
-- Richard
--
"Considerat ion shall be given to the need for as many as 32 characters
in some alphabets" - X3.4, 1963. This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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If malloc fails what should I do?
1. Exit imediately.
2. Print an error message (or put a log entry) and exit.
3. Print an error message (or put a log entry) and continue
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Printing an error message might be difficult in a graphical environment.
--
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