git 9c501935a3cd broke the strace build.

From: Rob Landley
Date: Thu Jan 14 2010 - 05:57:13 EST

> net: Support inclusion of <linux/socket.h> before <sys/socket.h>
> The following user-space program fails to compile:
> #include <linux/socket.h>
> #include <sys/socket.h>

Did it ever? Isn't #including both sys/thingy and a linux/thingy in the same
program considered bad form?

> int main() { return 0; }
> The reason is that <linux/socket.h> tests __GLIBC__ to decide whether it
> should define various structures and macros that are now defined for
> user-space by <sys/socket.h>, but __GLIBC__ is not defined if no libc
> headers have yet been included.

Specifically, one of the tests was !__GLIBC__, I.E. checking that we _haven't_
included any of glibc's headers yet, which is presumably how you broke the
strace 4.5.18 ./configure test checking for the existence of the
linux/netlink.h file. (That test #includes stddef.h, linux/socket.h, and
linux/netlink.h and nothing else. Since stddef.h is a gcc header and not a
glibc header, __GLIBC__ isn't defined for the test code and thus that used to
work under 2.5.31. Now under 2.6.32 it dies with:

linux/netlink.h:35: error: expected specifier-qualifier-list before

And later on the strace build breaks because it doesn't #include
linux/netlink.h when it needs to. (Why yes, autoconf _is_ brittle and near-
useless, thanks for noticing.)

*shrug* I can patch the strace ./configure to include bits/socket.h instead of
linux/socket.h, but what I can't understand is why _you_ couldn't. (What use
case did this patch actually fix? Would reversing the order of those two
headers have helped?)

Latency is more important than throughput. It's that simple. - Linus Torvalds

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