Re: [dpdk-dev] [PATCH] Make -Werror optional

[Panu Matilainen <pmatilai@redhat.com>]

On 02/12/2015 04:38 PM, Stephen Hemminger wrote:
> On Thu, 12 Feb 2015 13:13:22 +0200
> Panu Matilainen <pmatilai@redhat.com> wrote:
>
>> This adds new CONFIG_RTE_ERROR_ON_WARNING config option to enable
>> fail-on-warning compile behavior, defaulting to off.
>>
>> Failing build on warnings is a useful developer tool but its bad
>> for release tarballs which can and do get built with newer
>> compilers than what was used/available during development. Compilers
>> routinely add new warnings so code which built silently with cc X
>> might no longer do so with X+1. This doesn't make the existing code
>> any more buggier and failing the build in this case does not help
>> not help improve code quality of an already released version either.
>> ---
>>   config/common_bsdapp           | 1 +
>>   config/common_linuxapp         | 1 +
>>   mk/toolchain/clang/rte.vars.mk | 5 ++++-
>>   mk/toolchain/gcc/rte.vars.mk   | 5 ++++-
>>   mk/toolchain/icc/rte.vars.mk   | 6 +++++-
>>   5 files changed, 15 insertions(+), 3 deletions(-)
>>
>> diff --git a/config/common_bsdapp b/config/common_bsdapp
>> index 57bacb8..a5687b3 100644
>> --- a/config/common_bsdapp
>> +++ b/config/common_bsdapp
>> @@ -362,6 +362,7 @@ CONFIG_RTE_KNI_VHOST_DEBUG_TX=n
>>   # Enable warning directives
>>   #
>>   CONFIG_RTE_INSECURE_FUNCTION_WARNING=n
>> +CONFIG_RTE_ERROR_ON_WARNING=n
>>
>>   #
>>   # Compile the test application
>> diff --git a/config/common_linuxapp b/config/common_linuxapp
>> index d428f84..0762f99 100644
>> --- a/config/common_linuxapp
>> +++ b/config/common_linuxapp
>> @@ -383,6 +383,7 @@ CONFIG_RTE_LIBRTE_XEN_DOM0=n
>>   # Enable warning directives
>>   #
>>   CONFIG_RTE_INSECURE_FUNCTION_WARNING=n
>> +CONFIG_RTE_ERROR_ON_WARNING=n
>>
>>   #
>>   # Compile the test application
>> diff --git a/mk/toolchain/clang/rte.vars.mk b/mk/toolchain/clang/rte.vars.mk
>> index 40cb389..12726e7 100644
>> --- a/mk/toolchain/clang/rte.vars.mk
>> +++ b/mk/toolchain/clang/rte.vars.mk
>> @@ -63,11 +63,14 @@ TOOLCHAIN_ASFLAGS =
>>   TOOLCHAIN_CFLAGS =
>>   TOOLCHAIN_LDFLAGS =
>>
>> -WERROR_FLAGS := -W -Wall -Werror -Wstrict-prototypes -Wmissing-prototypes
>> +WERROR_FLAGS := -W -Wall -Wstrict-prototypes -Wmissing-prototypes
>>   WERROR_FLAGS += -Wmissing-declarations -Wold-style-definition -Wpointer-arith
>>   WERROR_FLAGS += -Wnested-externs -Wcast-qual
>>   WERROR_FLAGS += -Wformat-nonliteral -Wformat-security
>>   WERROR_FLAGS += -Wundef -Wwrite-strings
>> +ifeq ($(CONFIG_RTE_ERROR_ON_WARNING),y)
>> +WERROR_FLAGS += -Werror
>> +endif
>>
>>   # process cpu flags
>>   include $(RTE_SDK)/mk/toolchain/$(RTE_TOOLCHAIN)/rte.toolchain-compat.mk
>> diff --git a/mk/toolchain/gcc/rte.vars.mk b/mk/toolchain/gcc/rte.vars.mk
>> index 88f235c..bbd3c85 100644
>> --- a/mk/toolchain/gcc/rte.vars.mk
>> +++ b/mk/toolchain/gcc/rte.vars.mk
>> @@ -71,11 +71,14 @@ ifeq (,$(findstring -O0,$(EXTRA_CFLAGS)))
>>   endif
>>   endif
>>
>> -WERROR_FLAGS := -W -Wall -Werror -Wstrict-prototypes -Wmissing-prototypes
>> +WERROR_FLAGS := -W -Wall -Wstrict-prototypes -Wmissing-prototypes
>>   WERROR_FLAGS += -Wmissing-declarations -Wold-style-definition -Wpointer-arith
>>   WERROR_FLAGS += -Wcast-align -Wnested-externs -Wcast-qual
>>   WERROR_FLAGS += -Wformat-nonliteral -Wformat-security
>>   WERROR_FLAGS += -Wundef -Wwrite-strings
>> +ifeq ($(CONFIG_RTE_ERROR_ON_WARNING),y)
>> +WERROR_FLAGS += -Werror
>> +endif
>>
>>   # process cpu flags
>>   include $(RTE_SDK)/mk/toolchain/$(RTE_TOOLCHAIN)/rte.toolchain-compat.mk
>> diff --git a/mk/toolchain/icc/rte.vars.mk b/mk/toolchain/icc/rte.vars.mk
>> index e39d710..652cca8 100644
>> --- a/mk/toolchain/icc/rte.vars.mk
>> +++ b/mk/toolchain/icc/rte.vars.mk
>> @@ -69,8 +69,12 @@ TOOLCHAIN_ASFLAGS =
>>   #   error #13368: loop was not vectorized with "vector always assert"
>>   #   error #15527: loop was not vectorized: function call to fprintf cannot be vectorize
>>   #                   was declared "deprecated"
>> -WERROR_FLAGS := -Wall -Werror-all -w2 -diag-disable 271 -diag-warning 1478
>> +WERROR_FLAGS := -Wall -w2 -diag-disable 271 -diag-warning 1478
>>   WERROR_FLAGS += -diag-disable 13368 -diag-disable 15527
>> +ifeq ($(CONFIG_RTE_ERROR_ON_WARNING),y)
>> +WERROR_FLAGS += -Werror-all
>> +endif
>> +
>>
>>   # process cpu flags
>>   include $(RTE_SDK)/mk/toolchain/$(RTE_TOOLCHAIN)/rte.toolchain-compat.mk
>
> The -Werror is a real feature. Having dealt with legacy code where
> there are lots of bugs which were already warnings being ignored, having
> a big hard stop when errors are found is really good.
>
> The default should be on but I understand why you may want to turn it
> off, but it should require some effort to do.

I wholeheartedly agree with all that, when applied the developers of the 
codebase. I spent the last 7+ years of my life working on a piece of 
software that emitted well over six hundred "harmless" warnings on build 
when I started with it, trust me I have very little tolerance for 
introducing new compiler warnings.

But placing that burden to users trying to compile a released version of 
the software does good to nobody.

	- Panu -