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From: Alex =?utf-8?Q?Benn=C3=A9e?= <alex.bennee@linaro.org>
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Date: Fri, 02 Jun 2017 16:49:07 +0100
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Subject: Re: [Qemu-devel] [PATCH 0/2] Fix compilation dependency issues of
 CONFIG_ARM_V7M
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: Wei Huang <wei@redhat.com>, qemu-arm <qemu-arm@nongnu.org>, QEMU Developers <qemu-devel@nongnu.org>


Peter Maydell <peter.maydell@linaro.org> writes:

> On 28 April 2017 at 14:58, Wei Huang <wei@redhat.com> wrote:
>> Using #ifdef is indeed a cleaner solution. However I can't use "#ifdef
>> CONFIG_ARM_V7M" & co inside target/arm/cpu.c file because CONFIG_xxx
>> aren't available as preprocessor directives. From what I saw the
>> CONFIG_xxx options can only control compiling source file. One solution
>> is to extract out all v7M code into separate files and use
>> CONFIG_ARM_V7M to direct compilation. A bit messy though. Any other
>> suggestions?
>
> We seem to run into "CONFIG_FOO is defined for make but not
> for the C preprocessor" from time to time, so maybe we should
> fix that?

Hmm is should be auto-generated from config-(host|target).mak but I've
never quite figured out why we need timestamps rather than a straight
dependency check in rules.mk:

  # Generate timestamp files for .h include files

  config-%.h: config-%.h-timestamp
          @cmp $< $@ >/dev/null 2>&1 || cp $< $@

  config-%.h-timestamp: config-%.mak $(SRC_PATH)/scripts/create_config
          $(call quiet-command, sh $(SRC_PATH)/scripts/create_config < $< > $@,"GEN","$(TARGET_DIR)config-$*.h")

This seems to be one of those things that goes away on a make clean && rebuild

--
Alex Bennée