From: ratheesh kannoth <ratheesh.ksz@gmail.com>
To: Daniel Baluta <daniel.baluta@gmail.com>
Cc: Randi Botse <nightdecoder@gmail.com>,
linux-c-programming@vger.kernel.org
Subject: Re: malloc question
Date: Tue, 26 Apr 2011 16:24:05 +0530 [thread overview]
Message-ID: <BANLkTinW-j2DiwbVC5u8BfJMU7jK3_KbwA@mail.gmail.com> (raw)
In-Reply-To: <BANLkTikCz0uyFkU2Df-hiAmmj+-ZRABdVQ@mail.gmail.com>
On Tue, Apr 26, 2011 at 4:10 PM, Daniel Baluta <daniel.baluta@gmail.com> wrote:
> On Tue, Apr 26, 2011 at 1:33 PM, Randi Botse <nightdecoder@gmail.com> wrote:
>> Hi All,
>>
>> I want to ask malloc() behaviour, consider these codes;
>>
>> ...
>> char *ptr = malloc(1);
>> strcpy(ptr, "what");
>> puts(ptr);
>> ....
>>
>> Confusingly, the strcpy() copied all bytes to ptr, but I just manage
>> to allocate ptr only for 1 byte, I guess I will have segfault here,
>> why this happen? why the string successfully copied into ptr? , is
>> those code legal?
>
> You didn't get segfault because you were lucky.
>
> Memory is allocated in multiples of page size (usually 4K).
> The memory after your allocated byte is valid in your case.
>
> thanks,
> Daniel.
> --
U could read a little more about vm_page_struct. ( virtual address
space to physical page ). Try below code also for more
clarification.....
char *ptr = malloc(1);
strcpy(ptr, "what");
free(ptr);
strcpy(ptr, "hell");
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next prev parent reply other threads:[~2011-04-26 10:54 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-26 10:33 malloc question Randi Botse
2011-04-26 10:40 ` Daniel Baluta
2011-04-26 10:54 ` ratheesh kannoth [this message]
2011-04-26 10:57 ` Daniel Baluta
2011-04-26 11:50 ` ratheesh kannoth
2011-04-26 15:05 ` Glynn Clements
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