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To: Thomas Monjalon <thomas.monjalon@6wind.com>,
 =?UTF-8?Q?Simon_K=c3=a5gstr=c3=b6m?= <simon.kagstrom@netinsight.net>
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From: Panu Matilainen <pmatilai@redhat.com>
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Date: Mon, 7 Dec 2015 10:33:24 +0200
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Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH v2] mk: pass EXTRA_CFLAGS to AUTO_CPUFLAGS to
 enable local modifications
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On 12/04/2015 08:53 PM, Thomas Monjalon wrote:
>>>> We have encountered a CPU where the AES-NI instruction set is disabled
>>>> due to export restrictions. Since the build machine and target machine
>>>> is different, using -native configs doesn't work, and on this CPU, the
>>>> application refuses to run due to the AES CPU flags being amiss.
>>>>
>>>> The patch passes EXTRA_CFLAGS to the figure-out-cpu-flags helper,
>>>> which allows us to add -mno-aes to the compile flags and resolve this
>>>> problem.
>>>>
>>>> Signed-off-by: Simon Kagstrom <simon.kagstrom@netinsight.net>
>>
>> Acked-by: Olivier Matz <olivier.matz@6wind.com>
>
> Applied, thanks
>

This causes some complications on Fedora/RHEL due to fairly complex 
interactions with -Werror, -Wall and -Wformat-security mixup between 
upstream- and distro default compiler flags.

More specifically, when EXTRA_CFLAGS contains warning flag manipulation 
this patch can cause mismatch between other options that are okay 
elsewhere in dpdk make. A simple fix is to pass WERROR_FLAGS to 
AUTO_CPUFLAGS too to counter this, ie

diff --git a/mk/rte.cpuflags.mk b/mk/rte.cpuflags.mk
index c6bb8de..28f203b 100644
--- a/mk/rte.cpuflags.mk
+++ b/mk/rte.cpuflags.mk
@@ -33,7 +33,7 @@
  # used to set the RTE_CPUFLAG_* environment variables giving details
  # of what instruction sets the target cpu supports.

-AUTO_CPUFLAGS := $(shell $(CC) $(MACHINE_CFLAGS) $(EXTRA_CFLAGS) -dM -E 
- < /dev/null)
+AUTO_CPUFLAGS := $(shell $(CC) $(MACHINE_CFLAGS) $(WERROR_FLAGS) 
$(EXTRA_CFLAGS) -dM -E - < /dev/null)

  # adding flags to CPUFLAGS


I can send an official patch if this seems acceptable.

	- Panu -