[OE-core] [PATCH] gcc-7.inc: add new warning "Wnot-cross-compiler"

[Khem Raj]

On Tue, Jul 18, 2017 at 8:33 PM, Andre McCurdy <armccurdy at gmail.com> wrote:
> On Tue, Jul 18, 2017 at 5:12 PM, Khem Raj <raj.khem at gmail.com> wrote:
>>
>> On Tue, Jul 18, 2017 at 6:45 PM Juro Bystricky <juro.bystricky at intel.com>
>> wrote:
>>>
>>> Suppose we have an autotools project that looks like it is using the cross
>>> compiler but is actually reaching out to the host compiler instead.
>>> On an x86-64 build, you may not even notice.
>>> To be able to prevent this, this patch implements a new gcc warning
>>> "Wnot-cross-compiler". The intention here is to intentionally break a
>>> build
>>> if we are not using a cross-compiler when one is expected to be used.
>>>
>>> Expected usage: " -Wnot-cross-compiler -Werror=not-cross-compiler "will
>>
>> Shouldn't this patch get applied to native gcc on build hosts ?
>
> Isn't the intention that native gcc won't recognise the new options
> and will therefore fail if they're accidentally passed to it?

precisely, the problem is that some host compiler may silently ignore
unknown warnings and some host may not be using gcc as default system
compiler at all e.g. mageia distro and may be more in future.

>
>> And I would suggest to sent it to gcc mailing lists before we apply it to oe
>>>
>>> [YOCTO #11587]
>>>
>>> Signed-off-by: Juro Bystricky <juro.bystricky at intel.com>
>>> ---
>>>  meta/recipes-devtools/gcc/gcc-7.1.inc              |  1 +
>>>  .../gcc/gcc-7.1/0051-warn-not-cross-compiler.patch | 39
>>> ++++++++++++++++++++++
>>>  2 files changed, 40 insertions(+)
>>>  create mode 100644
>>> meta/recipes-devtools/gcc/gcc-7.1/0051-warn-not-cross-compiler.patch
>>>
>>> diff --git a/meta/recipes-devtools/gcc/gcc-7.1.inc
>>> b/meta/recipes-devtools/gcc/gcc-7.1.inc
>>> index 3f1c06d..e9b1f21 100644
>>> --- a/meta/recipes-devtools/gcc/gcc-7.1.inc
>>> +++ b/meta/recipes-devtools/gcc/gcc-7.1.inc
>>> @@ -75,6 +75,7 @@ SRC_URI = "\
>>>             file://0048-gcc-Enable-static-PIE.patch \
>>>
>>> file://0049-libsanitizer-Use-stack_t-instead-of-struct-sigaltsta.patch \
>>>             file://0050-replace-struct-ucontext-with-ucontext_t.patch \
>>> +           file://0051-warn-not-cross-compiler.patch \
>>>             ${BACKPORTS} \
>>>  "
>>>  BACKPORTS = "\
>>> diff --git
>>> a/meta/recipes-devtools/gcc/gcc-7.1/0051-warn-not-cross-compiler.patch
>>> b/meta/recipes-devtools/gcc/gcc-7.1/0051-warn-not-cross-compiler.patch
>>> new file mode 100644
>>> index 0000000..78671ed
>>> --- /dev/null
>>> +++ b/meta/recipes-devtools/gcc/gcc-7.1/0051-warn-not-cross-compiler.patch
>>> @@ -0,0 +1,39 @@
>>> +
>>> +This patch implements an additional gcc command line option warning
>>> +"Wnot-cross-compiler". The option (if specified) will simply generate
>>> +a warning if gcc being used is not a cross-compiler.
>>> +
>>> +Upstream-Status: Pending
>>> +Signed-off-by: Juro Bystricky <juro.bystricky at intel.com>
>>> +
>>> +
>>> +diff --git a/gcc/common.opt b/gcc/common.opt
>>> +--- a/gcc/common.opt
>>> ++++ b/gcc/common.opt
>>> +@@ -801,6 +801,10 @@
>>> + Common Var(warn_vector_operation_performance) Warning
>>> + Warn when a vector operation is compiled outside the SIMD.
>>> +
>>> ++Wnot-cross-compiler
>>> ++Common Warning
>>> ++Warn when not-cross-compiling.
>>> ++
>>> + Xassembler
>>> + Driver Separate
>>> +
>>> +diff --git a/gcc/opts.c b/gcc/opts.c
>>> +--- a/gcc/opts.c
>>> ++++ b/gcc/opts.c
>>> +@@ -2334,6 +2334,12 @@
>>> +       opts->x_flag_ipa_icf_variables = value;
>>> +       break;
>>> +
>>> ++    case OPT_Wnot_cross_compiler:
>>> ++#ifndef CROSS_DIRECTORY_STRUCTURE
>>> ++      warning (OPT_Wnot_cross_compiler, "Not using cross-compiler!");
>>> ++#endif
>>> ++      break;
>>> ++
>>> +     default:
>>> +       /* If the flag was handled in a standard way, assume the lack of
>>> +        processing here is intentional.  */
>>> --
>>> 2.7.4
>>>
>>
>> --
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