Re: [dpdk-dev] [dpdk-stable] [PATCH v5 1/2] mk: fix cross build errors

[Gavin Hu <Gavin.Hu@arm.com>]

> -----Original Message-----
> From: Bruce Richardson <bruce.richardson@intel.com>
> Sent: Tuesday, May 29, 2018 11:00 PM
> To: Thomas Monjalon <thomas@monjalon.net>
> Cc: Gavin Hu <Gavin.Hu@arm.com>; dev@dpdk.org
> Subject: Re: [dpdk-stable] [dpdk-dev] [PATCH v2 1/2] mk: fix cross build
> errors
>
> On Tue, May 29, 2018 at 04:45:55PM +0200, Thomas Monjalon wrote:
> > 28/05/2018 15:24, Bruce Richardson:
> > > Would a simpler solution for this not be to put "-Wno-implicit-
> fallthrough"
> > > for pmdinfogen? GCC will not give a warning for an unrecognised "-Wno"
> > > flag when compiling, unless there are other errors. This means we
> > > can just use the flag without bothering with version checks.
> >
> > No, it does not work.
> > I have this error with clang 5.0.1:
> >     error: unknown warning option '-Wno-format-truncation'
> >
> Yes, you still need to check for GCC to use the flag, just not for a specific
> version of GCC.
>
> /Bruce
[Gavin Hu] Hi Thomas, '-Wno-format-truncation' is applied to gcc only, not to clang.
Gcc, icc and clang have their own WERROR_FLAGS, they should not mix up with each other.

@Bruce,
Yes, in this sense, I am really concerned about to add -Wno-implicit-fallthrough option in the pmdinfogen Makefile, as it impacts not only gcc, but also clang and icc.
Maybe this not a best solution, as maybe it is not supported by all compilers. So should I fall back to the previous patch which check for the gcc version and apply the options for gcc only?

toolchain/clang/rte.vars.mk:38:WERROR_FLAGS := -W -Wall -Wstrict-prototypes -Wmissing-prototypes
toolchain/clang/rte.vars.mk:39:WERROR_FLAGS += -Wmissing-declarations -Wold-style-definition -Wpointer-arith
toolchain/clang/rte.vars.mk:40:WERROR_FLAGS += -Wnested-externs -Wcast-qual
toolchain/clang/rte.vars.mk:41:WERROR_FLAGS += -Wformat-nonliteral -Wformat-security
toolchain/clang/rte.vars.mk:42:WERROR_FLAGS += -Wundef -Wwrite-strings -Wdeprecated
toolchain/clang/rte.vars.mk:45:WERROR_FLAGS += -Werror
toolchain/clang/rte.vars.mk:52:WERROR_FLAGS += -Wno-missing-field-initializers
toolchain/clang/rte.vars.mk:56:WERROR_FLAGS += -Wno-address-of-packed-member
toolchain/gcc/rte.vars.mk:46:WERROR_FLAGS := -W -Wall -Wstrict-prototypes -Wmissing-prototypes
toolchain/gcc/rte.vars.mk:47:WERROR_FLAGS += -Wmissing-declarations -Wold-style-definition -Wpointer-arith
toolchain/gcc/rte.vars.mk:48:WERROR_FLAGS += -Wcast-align -Wnested-externs -Wcast-qual
toolchain/gcc/rte.vars.mk:49:WERROR_FLAGS += -Wformat-nonliteral -Wformat-security
toolchain/gcc/rte.vars.mk:50:WERROR_FLAGS += -Wundef -Wwrite-strings -Wdeprecated
toolchain/gcc/rte.vars.mk:53:WERROR_FLAGS += -Werror
toolchain/gcc/rte.vars.mk:59:WERROR_FLAGS += -Wno-error=cast-align
toolchain/gcc/rte.vars.mk:67:WERROR_FLAGS += -Wno-missing-field-initializers
toolchain/gcc/rte.vars.mk:71:WERROR_FLAGS += -Wno-uninitialized
toolchain/gcc/rte.vars.mk:76:WERROR_FLAGS += -Wimplicit-fallthrough=2
toolchain/gcc/rte.vars.mk:78:WERROR_FLAGS += -Wno-format-truncation

I tried at my side with clang-3.5 on X86 and clang-6.0 on ARM64. The buildings were successful. Unfortunately I did not have clang-5.0 machines.
clang -Wp,-MD,./.pmdinfogen.o.d.tmp  -Wno-implicit-fallthrough -W -Wall -Wstrict-prototypes -Wmissing-prototypes -Wmissing-declarations -Wold-style-definition -Wpointer-arith -Wnested-externs -Wcast-qual -Wformat-nonliteral -Wformat-security -Wundef -Wwrite-strings -Wdeprecated -Werror -Wno-missing-field-initializers -g -I/home/gavin/community/dpdk/build/include    -o pmdinfogen.o -c /home/gavin/community/dpdk/buildtools/pmdinfogen/pmdinfogen.c

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