[Mesa-dev] [PATCH] nir/builder: fix C90 build errors

Connor Abbott cwabbott0 at gmail.com
Sat Dec 19 19:30:28 PST 2015

On Sat, Dec 19, 2015 at 10:19 PM, Rob Clark <robdclark at gmail.com> wrote:
> On Sat, Dec 19, 2015 at 10:05 PM, Connor Abbott <cwabbott0 at gmail.com> wrote:
>> On Sat, Dec 19, 2015 at 9:52 PM, Rob Clark <robdclark at gmail.com> wrote:
>>> On Sat, Dec 19, 2015 at 9:30 PM, Connor Abbott <cwabbott0 at gmail.com> wrote:
>>>> On Sat, Dec 19, 2015 at 9:18 PM, Rob Clark <robdclark at gmail.com> wrote:
>>>>> Note that this is *only* about the header files.. not the src files.
>>>>> I'm not proposing to make NIR support C90.
>>>> Why would you need to only make the header filef C90 compliant? If you
>>>> just need to pass around a nir_shader * or something, you can just use
>>>> a forward declaration.
>>> turns out we happen to want structs, fxn prototypes, etc..  ie. what
>>> happens to be in the header ;-)
>>> I guess there is possibly a way to make it so that we build certain
>>> files w/ different warning flags or something (but dropping -Werror
>>> seems like the wrong thing).  At any rate, that sounds harder than a
>>> trivial few line patch.  And as long as it is trivial to keep the nir
>>> headers C90-clean, that seems like the better thing to do.  I mean, we
>>> already take some precautions in the header files to keep them usable
>>> from c++..
>> Yes, we make it C++-safe because a few parts of core NIR are written
>> in C++ (glsl-to-nir) as well as i965. On the other hand, we've always
>> allowed declarations mixed with code in NIR since day one, and making
>> the requirements on the header different from the requirements on
>> everything else is confusing and inconsistent.
> But we already have "confusing and inconsistent" (in quotes, since I
> don't think it is nearly as bad as you are making it out to be) thanks
> to the C++ requirement..

No, it's not. NIR contains both C++ and C99 code. Now, you're saying
you want a few things to be C90, despite the fact that the C90 parts
are useless without the C99 parts, so you obviously already have a
C99-capable compiler... why?

>>>>> I will at some point, before it is ready to merge, need to arrange the
>>>>> NIR related bits in mesa st so that we can build without it, for
>>>>> benefit of the MSVC folks.
>>>>> (It might be useful someday to use NIR more extensively in mesa st,
>>>>> and use nir->tgsi pass, so we can do all the opt passes in NIR..
>>>>> although that is *way* more ambitious than what I want to do right
>>>>> now.  With any luck, by the time we get to that point, we can rely on
>>>>> a less braindead version of MSVC?)
>>>> My understanding is that mesa/st doesn't need to be built with old
>>>> MSVC, just gallium.
>>> Oh, ok, if that is in fact the case, it simplifies some things.  Tbh
>>> I'm not 100% clear on what parts are used on windows..
>>> But like I said, if it is just trivial things to keep the nir headers
>>> C90-clean, then why not just do that?  I mean, if you have something
>>> planned that would actually make it a burden to keep the headers
>>> C90-clean we can revisit, but I can't really imagine what that would
>>> be.  Usually the static-inline stuff tends to be relatively simple
>>> stuff (since you aren't wanting to duplicate a lot of complex stuff in
>>> many object files).
>> Just because it's trivial to fix doesn't mean that it won't break in
>> the future. Now, the build is going to break every time someone adds
>> something to nir.h that happens to use some C99 features and doesn't
>> test gallium, all because a few files have an unnecessary extra
>> -Werror. Let's just fix the root problem instead.
> -Werror is not the problem.. maybe lack of --std=c99 is.. but defn not -Werror
> Are there *really* that many people making changes to nir, who are
> building mesa without gallium?  I think we've already convinced most
> people making changes on NIR that they should be building
> vc4/freedreno (which requires building gallium) to avoid the sort of
> breakage that has already happened a couple times.  And if they
> aren't, they should be.  And since this is all compile-time issues,
> rather than runtime, I kind of think you are making a mountain out of
> a mole-hill here..

We've convinced people to check *when their changes might affect those
drivers*. In the past, merely adding an inline function to a NIR
header didn't qualify for that, since we managed to keep the build
requirements relatively consistent between gallium and non-gallium...
for now. Again, why don't you just fix the build system?

> BR,
> -R
>>>>> On Sat, Dec 19, 2015 at 8:58 PM, Connor Abbott <cwabbott0 at gmail.com> wrote:
>>>>>> We haven't allowed NIR in core gallium before, since core gallium has
>>>>>> to be built with some old version of MSVC that doesn't support many
>>>>>> C99 features that we really wanted to use. The only reason that
>>>>>> -Werror exists is for compatibility with old MSVC, and if you want to
>>>>>> use NIR with something that needs to build with old MSVC, there are
>>>>>> going to be much bigger changes needed, and we'd rather avoid that. If
>>>>>> you just want to add some NIR-specific stuff that e.g. softpipe
>>>>>> doesn't need to compile against, then you should fix the build system
>>>>>> not to add the warning.
>>>>>> On Sat, Dec 19, 2015 at 5:39 PM, Rob Clark <robdclark at gmail.com> wrote:
>>>>>>> From: Rob Clark <robclark at freedesktop.org>
>>>>>>> We are going to start using nir_builder.h from some gallium code, which
>>>>>>> is currently only C90.  Which results in:
>>>>>>>    In file included from nir/nir_emulate.c:26:0:
>>>>>>>    ../../../src/glsl/nir/nir_builder.h: In function ‘nir_build_alu’:
>>>>>>>    ../../../src/glsl/nir/nir_builder.h:132:4: error: ISO C90 forbids mixed declarations and code [-Werror=declaration-after-statement]
>>>>>>>        unsigned num_components = op_info->output_size;
>>>>>>>        ^
>>>>>>>    In file included from nir/nir_emulate.c:26:0:
>>>>>>>    ../../../src/glsl/nir/nir_builder.h: In function ‘nir_ssa_for_src’:
>>>>>>>    ../../../src/glsl/nir/nir_builder.h:271:4: error: ISO C90 forbids mixed declarations and code [-Werror=declaration-after-statement]
>>>>>>>        nir_alu_src alu = { NIR_SRC_INIT };
>>>>>>>        ^
>>>>>>>    cc1: some warnings being treated as errors
>>>>>>> Signed-off-by: Rob Clark <robclark at freedesktop.org>
>>>>>>> ---
>>>>>>> Not sure if I should just go ahead and push this sort of thing.  Or
>>>>>>> if we can start requiring C99 for gallium?
>>>>>>>  src/glsl/nir/nir_builder.h | 7 +++++--
>>>>>>>  1 file changed, 5 insertions(+), 2 deletions(-)
>>>>>>> diff --git a/src/glsl/nir/nir_builder.h b/src/glsl/nir/nir_builder.h
>>>>>>> index 332bb02..6f30306 100644
>>>>>>> --- a/src/glsl/nir/nir_builder.h
>>>>>>> +++ b/src/glsl/nir/nir_builder.h
>>>>>>> @@ -115,6 +115,8 @@ nir_build_alu(nir_builder *build, nir_op op, nir_ssa_def *src0,
>>>>>>>  {
>>>>>>>     const nir_op_info *op_info = &nir_op_infos[op];
>>>>>>>     nir_alu_instr *instr = nir_alu_instr_create(build->shader, op);
>>>>>>> +   unsigned num_components;
>>>>>>> +
>>>>>>>     if (!instr)
>>>>>>>        return NULL;
>>>>>>> @@ -129,7 +131,7 @@ nir_build_alu(nir_builder *build, nir_op op, nir_ssa_def *src0,
>>>>>>>     /* Guess the number of components the destination temporary should have
>>>>>>>      * based on our input sizes, if it's not fixed for the op.
>>>>>>>      */
>>>>>>> -   unsigned num_components = op_info->output_size;
>>>>>>> +   num_components = op_info->output_size;
>>>>>>>     if (num_components == 0) {
>>>>>>>        for (unsigned i = 0; i < op_info->num_inputs; i++) {
>>>>>>>           if (op_info->input_sizes[i] == 0)
>>>>>>> @@ -265,10 +267,11 @@ nir_channel(nir_builder *b, nir_ssa_def *def, unsigned c)
>>>>>>>  static inline nir_ssa_def *
>>>>>>>  nir_ssa_for_src(nir_builder *build, nir_src src, int num_components)
>>>>>>>  {
>>>>>>> +   nir_alu_src alu = { NIR_SRC_INIT };
>>>>>>> +
>>>>>>>     if (src.is_ssa && src.ssa->num_components == num_components)
>>>>>>>        return src.ssa;
>>>>>>> -   nir_alu_src alu = { NIR_SRC_INIT };
>>>>>>>     alu.src = src;
>>>>>>>     for (int j = 0; j < 4; j++)
>>>>>>>        alu.swizzle[j] = j;
>>>>>>> --
>>>>>>> 2.5.0
>>>>>>> _______________________________________________
>>>>>>> mesa-dev mailing list
>>>>>>> mesa-dev at lists.freedesktop.org
>>>>>>> http://lists.freedesktop.org/mailman/listinfo/mesa-dev

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