[U-Boot] [RFC] C2011 standard for building U-Boot

[Heinrich Schuchardt]

Hello Tom,

for the UEFI implementation of U-Boot it would make defining string
constants much easier using the following C 2011 notation:

u16 *foo = u"My lovely string";

Do you see any reason forcing us not to use features of C 2011?

In /Makefile I found the following:

ifeq ($(HOSTOS),cygwin)
HOSTCFLAGS      += -ansi
endif

#
# Xtensa linker script cannot be preprocessed with -ansi because of
# preprocessor operations on strings that don't make C identifiers.
#
ifeq ($(CONFIG_XTENSA),)
LDPPFLAGS       += -ansi
endif

# Create a file containing the configuration options the image was built
with
quiet_cmd_cpp_cfg = CFG     $@
cmd_cpp_cfg = $(CPP) -Wp,-MD,$(depfile) $(cpp_flags) $(LDPPFLAGS) -ansi \
-DDO_DEPS_ONLY -D__ASSEMBLY__ -x assembler-with-cpp -P -dM -E -o $@ $<

The GCC documentation teaches:
-ansi: In C mode, this is equivalent to -std=c90. In C++ mode, it is
equivalent to -std=c++98.

When I am building for arm64 I find these options actually used:

  aarch64-linux-gnu-gcc -Wp,-MD,common/.cli_hush.o.d  -nostdinc -isystem
/usr/lib/gcc-cross/aarch64-linux-gnu/6/include -Iinclude
-I./arch/arm/include -include ./include/linux/kconfig.h -D__KERNEL__
-D__UBOOT__ -Wall -Wstrict-prototypes -Wno-format-security -fno-builtin
-ffreestanding -Os -fno-stack-protector -fno-delete-null-pointer-checks
-g -fstack-usage -Wno-format-nonliteral -Werror=date-time -D__ARM__
-fno-pic -mstrict-align -ffunction-sections -fdata-sections -fno-common
-ffixed-r9 -fno-common -ffixed-x18 -pipe -march=armv8-a
-D__LINUX_ARM_ARCH__=8 -I./arch/arm/mach-meson/include
-D"KBUILD_STR(s)=#s" -D"KBUILD_BASENAME=KBUILD_STR(cli_hush)"
-D"KBUILD_MODNAME=KBUILD_STR(cli_hush)" -c -o common/cli_hush.o
common/cli_hush.c

My impression is that:

We have variables in /Makefile that are not used for anything:
LDPPFLAGS, cmd_cpp_cfg, cmd_cpp_lds.

All lines refering to these variables should be removed.
Cf. https://lists.denx.de/pipermail/u-boot/2016-September/267177.html

We force C90 on cygwin to compile the host code but not for the actual
U-Boot code. Probably a remnant from a distant past.

So nothing should stop us from using C2011 in U-Boot.

Would you agree?

Best regards

Heinrich