Jason Ekstrand <ja...@jlekstrand.net> writes: > On Fri, Jun 26, 2015 at 12:08 PM, Francisco Jerez <curroje...@riseup.net> > wrote: >> Jason Ekstrand <ja...@jlekstrand.net> writes: >> >>> In C, if you partially initialize a structure, the rest of the struct gets >>> set to 0. C++, however, does not have this rule so GCC throws warnings >>> whenver NIR_SRC_INIT or NIR_DEST_INIT is used in C++. >> >> I don't think that's right, in C++ initializers missing from an >> aggregate initializer list are also defined to be initialized >> (value-initialized to be more precise, what would set them to zero in >> this case just like in C). > > Yes, that is correct. I just did a second attempt that, instead, > defines a static const variable named NIR_SRC_INIT with a partial > initializer. C++ still gets grumpy and gives me a pile of "missing > initializer" warnings. > That's likely related to the warning flags you have enabled in CXXFLAGS, not to C++ itself. Maybe you have -Wmissing-field-initializers enabled for C++ only?
>>> Since nir.h contains a static inline that uses NIR_SRC_INIT, every C++
>>> file that includes nir.h complains about this.
>>>
>> I suspect the reason why this causes a warning may be that you're using
>> compound literals? (which are a C99-specific feature and not part of C++)
>>
>>> This patch adds a small static inline function that makes a struct,
>>> memsets it to 0, and returns it. NIR_SRC_INIT and NIR_DEST_INIT are then
>>> wrappers around this function.
>>
>> In C++ you could just call the implicitly defined default constructor
>> for nir_src or nir_dest, like 'nir_src()'.
>
> The implicitly defined default constructor does nothing to POD types,
> so doing so would explicitly *not* perform the desired action of
> zeroing out the data.
>
Indeed, but 'nir_src()' doesn't only call the implicitly-defined trivial
default constructor, it value-initializes the object (See section 8.5/8
of the C++14 spec) what for POD types causes all members to be
zero-initialized.
>>> ---
>>> src/glsl/nir/nir.h | 22 ++++++++++++++++++++++
>>> 1 file changed, 22 insertions(+)
>>>
>>> diff --git a/src/glsl/nir/nir.h b/src/glsl/nir/nir.h
>>> index c666d93..3634f30 100644
>>> --- a/src/glsl/nir/nir.h
>>> +++ b/src/glsl/nir/nir.h
>>> @@ -511,7 +511,18 @@ typedef struct nir_src {
>>> bool is_ssa;
>>> } nir_src;
>>>
>>> +#ifdef __cplusplus
>>> +static inline nir_src
>>> +__nir_src_init(void)
>>> +{
>>> + nir_src src;
>>> + memset(&src, 0, sizeof(src));
>>> + return src;
>>> +}
>>> +#define NIR_SRC_INIT (__nir_src_init())
>>> +#else
>>> #define NIR_SRC_INIT (nir_src) { { NULL } }
>>> +#endif
>>>
>>> #define nir_foreach_use(reg_or_ssa_def, src) \
>>> list_for_each_entry(nir_src, src, &(reg_or_ssa_def)->uses, use_link)
>>> @@ -534,7 +545,18 @@ typedef struct {
>>> bool is_ssa;
>>> } nir_dest;
>>>
>>> +#ifdef __cplusplus
>>> +static inline nir_dest
>>> +__nir_dest_init(void)
>>> +{
>>> + nir_dest dest;
>>> + memset(&dest, 0, sizeof(dest));
>>> + return dest;
>>> +}
>>> +#define NIR_DEST_INIT (__nir_dest_init())
>>> +#else
>>> #define NIR_DEST_INIT (nir_dest) { { { NULL } } }
>>> +#endif
>>>
>>> #define nir_foreach_def(reg, dest) \
>>> list_for_each_entry(nir_dest, dest, &(reg)->defs, reg.def_link)
>>> --
>>> 2.4.3
>>>
>>> _______________________________________________
>>> mesa-dev mailing list
>>> mesa-dev@lists.freedesktop.org
>>> http://lists.freedesktop.org/mailman/listinfo/mesa-dev
signature.asc
Description: PGP signature
_______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
