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[lwip-devel] [bug #27352] Change ip_addr from struct to typedef (u32_t)


From: Bill Auerbach
Subject: [lwip-devel] [bug #27352] Change ip_addr from struct to typedef (u32_t)
Date: Fri, 29 Jan 2010 13:54:41 +0000
User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.7) Gecko/20091221 Firefox/3.5.7 (.NET CLR 3.5.30729)

Follow-up Comment #7, bug #27352 (project lwip):

When I looked into this, I noticed that all references to an ip_addr within a
payload are within a packet and so it works out to be 32-bit aligned.  I am
running on an alignment required processor with the following:

struct ip_addr {
  u32_t addr;
};

There is no alignment or packing specified in this struct which makes it
equivalent to replacing it with u32_t. I'm using TCP and UDP.  One compiler
for sure (GCC) handles this much more efficiently - it will load a 32-bit word
- otherwise with packing specified it loads 4 bytes ANDing shifting and ORing
into the address.

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