[ovs-dev] [PATCH] Fix detection of vhost_cuse in dpdk rte_config.h

Mussar, Gary gmussar at ciena.com
Wed Jul 22 19:03:45 UTC 2015


Sorry, I missed this email when it first came in. The use of AC_LANG_PUSH and AC_LANG_POP come from previous bad experiences with macros setting other languages. I usually consider it good practice to not assume the C language has been previously set.

It is quite possible that nothing in OVS sets a different language in any of the existing macros today so you might safely get rid of these 2 lines. However, these lines ensure the correct language is used whether some other macro changes the language or not.

Gary

-----Original Message-----
From: Ben Pfaff [mailto:blp at nicira.com] 
Sent: Thursday, July 16, 2015 16:21
To: Mussar, Gary
Cc: dev at openvswitch.org
Subject: Re: [ovs-dev] [PATCH] Fix detection of vhost_cuse in dpdk rte_config.h

On Mon, Jul 06, 2015 at 05:41:38PM -0400, Mussar, Gary wrote:
> Fix detection of vhost_cuse in dpdk rte_config.h
> 
> Dpdk allows users to create a config that includes other config files 
> and then override values.
> 
> Eg.
> defconfig_x86_64-native_vhost_cuse-linuxapp-gcc:
> 
> CONFIG_RTE_BUILD_COMBINE_LIBS=y
> CONFIG_RTE_BUILD_SHARED_LIB=n
> CONFIG_RTE_LIBRTE_VHOST=y
> CONFIG_RTE_LIBRTE_VHOST_USER=n
> 
> This allows you to have both a vhostuser and vhostcuse config in the 
> same source tree without the need to replicate everything in those 
> config files just to change a couple of settings. The resultant 
> .config file has all of the settings from the included files with the updated settings at the end.
> The resultant rte_config.h contains multiple undefs and defines for 
> the overridden settings.
> 
> Eg.
> > grep RTE_LIBRTE_VHOST_USER 
> > x86_64-native_vhost_cuse-linuxapp-gcc/include/rte_config.h
> 
> The current mechanism to detect the RTE_LIBRTE_VHOST_USER setting 
> merely greps the rte_config.h file for the string "define RTE_LIBRTE_VHOST_USER 1"
> rather than the final setting of RTE_LIBRTE_VHOST_USER. The following 
> patch changes this test to detect the final setting of RTE_LIBRTE_VHOST_USER.
> 
> Signed-off-by: Gary Mussar <gmussar at ciena.com>

Daniele asked me to shepherd this in, since I know Autoconf pretty well.

I have one question.  Why does this patch use AC_LANG_PUSH and AC_LANG_POP?

Thanks,

Ben.



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