I certainly wouldn't encourage anybody to use negative numbers for bit
mask values!
Why not just write an aligned memory allocator which stashes an extra
pointer in a known location for easy freeing?
void * aligned_malloc(size_t size, size_t align)
{
// allocate storage area with space for an extra pointer and alignment
void * mem = malloc(size + sizeof(void*) + (align - 1));
// point to the start of the aligned storage
void * ptr = (void **)((uintptr_t)(mem + (align - 1) + sizeof(void
*)) & ~(align - 1));
// store the address of the allocated memory prior to the aligned
storage
((void **) ptr)[-1] = mem;
return ptr;
}
void aligned_free(void *ptr)
{
free(((void**) ptr)[-1]);
}
On 18/07/2018 2:59 AM, Charles Mills wrote:
The lines beginning with * aren't C either <g>. You want void *realp ...
Also, your second and third lines combine pretty well into one.
Cpool *p = (Cpool *)((long)realp & -16));
No one ever said system programming in C was pretty.
Charles
-----Original Message-----
From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf
Of Steve Smith
Sent: Tuesday, July 17, 2018 11:44 AM
To: [email protected]
Subject: Re: S0C6 in CSRC4RG1
In assembler, STORAGE provides a BNDRY= keyword, which would be fine, but
this is a Metal C program. malloc provides no such thing. Don's
suggestion is doable, but it's fugly C code, and amounts to doing vascular
surgery wearing oven mitts:
*void realp = malloc(1408 + 15);
long ip = (long)realp & -16;
*Cpool p = (*CPool)ip;
Yeah, that's clear to anyone. Although I'm sure it could be obfuscated.
Note: If you think the 1st & 3rd lines are commented out, this thread is
not for you :-)
Problems:
1. Undocumented requirement to quad-word align CPOOL anchor and/or extent
in 64-bit mode (and actually undocumented alignment requirements for all).
2. Unable to guarantee quad-word alignment with malloc.
Ugh.
sas
On Tue, Jul 17, 2018 at 1:41 PM, Don Poitras <[email protected]> wrote:
Add 15 bytes to whatever length you are asking for and copy the
pointer. 'And' the last nibble to 0. Voila! quad-aligned pointer. :)
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