The memory allocator does not track how many bytes you requested.
Clib_mem_alloc(...) returns no less than the requested number of bytes. That’s
the API, contract, or promise depending on how you want to put it.
Clib_mem_realloc(...) always allocates a fresh chunk of memory and copies the
original data into the fresh chunk. It could use a clib_mem_size() check to
attempt to skip the allocate-and-copy operation. If the original object is
large enough to accommodate the realloc request, there’s no reason to do
anything.
However: clib_mem_realloc(...) is called in exactly one place in the code base,
and it’s known by construction that the case in question requires a new object.
Idiomatic vpp coding uses vectors instead of direct calls to the memory
allocator. Vectors know how many elements they contain. A u8 * vector would
likely amount to a drop-in replacement for whatever you’re doing.
We won’t be changing the memory allocator API / contract / promise to track the
original request size.
Dave
From: vpp-dev@lists.fd.io <vpp-dev@lists.fd.io> On Behalf Of
jiangxiaom...@outlook.com
Sent: Friday, August 28, 2020 11:11 PM
To: vpp-dev@lists.fd.io
Subject: Re: [vpp-dev] clib_mem_size return wrong mem size
Hi, Dave Barach:
I want to a realloc funtion like as bollow, the function args doesn't have
the original mem size, and clib_mem_size seems can't return the right memory
size. Is there any way to get the memory size ?
void *my_realloc(void *p, size_t s)
{
return p ? clib_mem_realloc(p, s, clib_mem_size(p)) : clib_mem_alloc(s);
}
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