Re: malloc was optimized out
Re: malloc was optimized out
- Subject: Re: malloc was optimized out
- From: Clark Cox <email@hidden>
- Date: Mon, 04 Jul 2016 15:26:46 -0700
> On Jul 4, 2016, at 13:58, Dmitry Markman <email@hidden> wrote:
>
> Hi Clark, FYI
>
> http://www.dii.uchile.cl/~daespino/files/Iso_C_1999_definition.pdf
I am *well* aware of what the standard says.
>
> 7.20.3.3 The malloc function
> . . . . .
> Description
> 2 The malloc function allocates space for an object
> whose size is specified by size and whose value is indeterminate.
> Returns
> 3 The malloc function returns either a null pointer
> or a pointer to the allocated space.
>
> so there is nothing in C standard about never returning NULL
Also note that there is nothing in the standard about *requiring* that NULL be returned. On a modern, UNIX system malloc will typically “succeed” and return a pointer to a not-yet-paged in block of memory. As far as the C standard is concerned, that malloc succeeded in allocating a block of memory. However, when you later go and access that memory, and the OS realizes that it can’t handle the resulting page-fault, your program crashes. This is a long-time, and well understood issue; and in light of that behavior, the compiler is 100% correct to do what it is doing.
>> On Jul 4, 2016, at 3:58 PM, Clark Cox <email@hidden> wrote:
>>
>> Malloc effectively *never* returns NULL.
Notice the word “effectively”.
--
Clark Smith Cox III
email@hidden
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