Re: [dpdk-dev] [PATCH v4 07/32] net/qede: fix 32 bit compilation

[Thomas Monjalon <thomas.monjalon@6wind.com>]

2016-10-26 21:01, Mody, Rasesh:
> > From: Thomas Monjalon [mailto:thomas.monjalon@6wind.com]
> > Sent: Wednesday, October 26, 2016 9:54 AM
> > 
> > 2016-10-18 21:11, Rasesh Mody:
> > > Fix 32 bit compilation for gcc version 4.3.4.
> > >
> > > Fixes: ec94dbc57362 ("qede: add base driver")
> > >
> > > Signed-off-by: Rasesh Mody <rasesh.mody@qlogic.com>
> > [...]
> > >  ifeq ($(CONFIG_RTE_TOOLCHAIN_GCC),y)
> > > +ifeq ($(shell gcc -Wno-unused-but-set-variable -Werror -E - <
> > > +/dev/null > /dev/null 2>&1; echo $$?),0)
> > >  CFLAGS_BASE_DRIVER += -Wno-unused-but-set-variable
> > > +endif
> > >  CFLAGS_BASE_DRIVER += -Wno-missing-declarations
> > > +ifeq ($(shell gcc -Wno-maybe-uninitialized -Werror -E - < /dev/null >
> > > +/dev/null 2>&1; echo $$?),0)
> > >  CFLAGS_BASE_DRIVER += -Wno-maybe-uninitialized
> > > +endif
> > >  CFLAGS_BASE_DRIVER += -Wno-strict-prototypes  ifeq ($(shell test
> > > $(GCC_VERSION) -ge 60 && echo 1), 1)  CFLAGS_BASE_DRIVER +=
> > > -Wno-shift-negative-value
> > 
> > What the hell are you doing here?
> 
> In one of our compilation testing on i586, we have gcc version 4.3.4. This version of gcc gives us following errors:
> 
> cc1: error: unrecognized command line option "-Wno-unused-but-set-variable"
> cc1: error: unrecognized command line option "-Wno-maybe-uninitialized"
> 
> -Wno-unused-but-set-variable option was added only in gcc version 5.1.0
> -Wno-maybe-uninitialized option was added only in gcc version 4.7.0
> 
> All that above change does is that it checks if -Wno-unused-but-set-variable and -Wno-maybe-uninitialized options are available with gcc only then include them for compilation.

Have you tried to look what is done for other drivers?
It is using GCC_VERSION to check the compatibility.

> > 1/ You should better fix "unused-but-set-variable" errors 2/ It won't work
> > when cross-compiling because you do not use $(CC)
> > 	in $(shell gcc
> 
> We tested on gcc version 6.2.0 on x86_64 without applying this patch. Errors related to "unused-but-set-variable" option were not seen. The only errors we saw are as noted above due to an older version of gcc.
> We do use $(shell gcc, however, it is used under ifeq ($(CONFIG_RTE_TOOLCHAIN_GCC),y), so, I believe it should work when cross-compiling. For example, in one of our compilation testing on clang version 3.8.0, with this patch applied, we did not see any errors. Please let us know if you see otherwise.

Cross-compilation is using $(CROSS) prefix, e.g. when compiling for ARM on x86.

> However, I do agree it is better to use $(CC). We could change that with a follow on patch.

Please fix this patch by using GCC_VERSION.