On 08/04/2017 03:53 PM, Rob Clark wrote: > On Fri, Aug 4, 2017 at 9:20 AM, Tom Rini <[email protected]> wrote: >> On Thu, Aug 03, 2017 at 06:27:02AM +0200, Heinrich Schuchardt wrote: >>> 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 >> >> OK. Drop 'em, throw travis-ci at it and see what, if anything, blows >> up. >> >>> 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. >> >> What's the minimum gcc (and llvm) version we need to use here? Thanks! >> > > It looks like probably gcc 4.9[1].. maybe 4.7 or even v4.6[2] is > complete enough for what we need.. that seems plenty old enough. I'm > less familiar with clang but wikipedia says 3.1[2]. > > If some board/arch was stuck on something older, I guess we could make > it a kconfig option that EFI_LOADER depends on. > > [1] https://gcc.gnu.org/wiki/C11Status > [2] https://en.wikipedia.org/wiki/C11_(C_standard_revision) > > BR, > -R >
Since gcc 4.7 the option -std=c11 is available. Since gcc 6.1 the default is -std=gnu11 (C2011 + gnu extensions) Cygwin provides gcc 6.3. Clang 2.9 has C11 suppport selected by -std=c11. Since Clang 3.6 switch to C11 by default. If it is compatible with the code base I think the best would be to explicitly set -std=c11. I will prepare a patch and test with Travis CI. Best regards Heinrich _______________________________________________ U-Boot mailing list [email protected] https://lists.denx.de/listinfo/u-boot
