[U-Boot] [PATCH v2] Makefile: adopt --std=gnu11 for HOSTCFLAGS on Linux

[Dr. Philipp Tomsich <philipp.tomsich@theobroma-systems.com>]

> On 14 May 2018, at 16:53, Mark Kettenis <mark.kettenis@xs4all.nl> wrote:
> 
>> From: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
>> Date: Mon, 14 May 2018 15:22:06 +0200
>> 
>> Following the conversion of the SPDX license tags, a number of files
>> compiled with -pedantic now generate warnings similar to the following
>> for using C99-style '//' comments in ISO C90 code:
>> 
>>  tools/gen_eth_addr.c:1:1: warning: C++ style comments are not allowed in ISO C90
>>   // SPDX-License-Identifier: GPL-2.0+
>>   ^
>> 
>> The SPDX comment-style change means that these files have adopted C99,
>> so need to change the language-standard to --std=gnu99 or --std=gnu11
>> to let the compiler know this.
>> 
>> As we now require GCC 6 or newer for the cross-compiler, the project has
>> implicitly moved the project to GNU11: let older GCC versions on various
>> Linux distros know to treat our host tools as GNU11 as well.
> 
> Note that the requirement is on the cross-compiler, not the host
> compiler.  On our "primary" architectures OpenBSD 6.3 ships with Clang
> 5.0.1 and the current development version uses Clang 6.0.0, which
> default to --std=gnu11.  I do hope those will continue to be supported
> as the host compiler…

Many of the files in question (e.g. lib/sha{1,256}.c) are shared between
the target and the host tools.

>> References: commit 83d290c56fab ("SPDX: Convert all of our single license tags to Linux Kernel style")
>> Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
>> ---
>> 
>> Changes in v2:
>> - Set '--std=gnu11' during compilation of host tools on Linux.
>> 
>> Makefile | 9 +++++++++
>> 1 file changed, 9 insertions(+)
>> 
>> diff --git a/Makefile b/Makefile
>> index f31ee60..d08fb6a 100644
>> --- a/Makefile
>> +++ b/Makefile
>> @@ -258,6 +258,15 @@ HOSTCFLAGS   = -Wall -Wstrict-prototypes -O2 -fomit-frame-pointer \
>> 		$(if $(CONFIG_TOOLS_DEBUG),-g)
>> HOSTCXXFLAGS = -O2
>> 
>> +# With the move to GCC 6, we have implicitly upgraded our language
>> +# standard to GNU11 (see https://gcc.gnu.org/gcc-5/porting_to.html).
>> +# Some Linux distributions (including RHEL7, SLES13, Debian 8) still
>> +# have older compilers as their default, so we make it explicit for
>> +# these that our host tools are GNU11 (i.e. C11 w/ GNU extensions).
>> +ifeq ($(HOSTOS),linux)
>> +HOSTCFLAGS += --std=gnu11
>> +endif
>> +
>> ifeq ($(HOSTOS),cygwin)
>> HOSTCFLAGS	+= -ansi
>> endif
>> -- 
>> 2.1.4
>> 
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