[Bug c++/42743] Inexplicable error message with constructing SIMD values

[Bug c++/42743] Inexplicable error message with constructing SIMD values

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42743

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jsm28 at gcc dot gnu.org

--- Comment #2 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-10-15 21:26:19 UTC ---
The first part of this I also noticed some time ago (and mentioned in another
PR): roughly speaking, __m128 doesn't seem default-constructible. Is there
something we can do about that? Seems rather weird, naively.

[Bug c++/42743] Inexplicable error message with constructing SIMD values

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=42743

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.7.0
           Keywords|                            |rejects-valid
         Resolution|---                         |FIXED
             Status|UNCONFIRMED                 |RESOLVED

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Been fixed since GCC 4.7.0.

[Bug c++/42743] New: Inexplicable error message with constructing SIMD values

[bisqwit at iki dot fi]

This code:

#include <emmintrin.h>

template<typename vec_t>
void x()
{
    vec_t tmp1 = vec_t(); // Works with myvec, causes error with __m128
    vec_t tmp2 = {};      // Causes warnings about uninitialized members in
myvec
    vec_t tmp3;           // This may cause a warning about use of
uninitialized variables if tmp3 is later read-accessed.
}


struct myvec
{
    struct tmp
    {
        float data[2];
    } d;
};
void y()
{
    x<__m128> ();
    x<myvec>   ();
}

Produces this error when vec_t is __m128:
tmp.cc:6: error: can't convert between vector values of different size
And this warning when vec_t is myvec:
tmp.cc:7: warning: missing initializer for member 'myvec::d'

It is my understanding that constructor calls should never be treated as syntax
errors. Is there really no way to write this code so that it causes neither a
compile error or a warning?


-- 
           Summary: Inexplicable error message with constructing SIMD values
           Product: gcc
           Version: 4.4.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: bisqwit at iki dot fi
 GCC build triplet: x86_64-pc-linux-gnu
  GCC host triplet: x86_64-pc-linux-gnu
GCC target triplet: x86_64-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42743

[Bug c++/42743] Inexplicable error message with constructing SIMD values

[jwakely dot gcc at gmail dot com]

------- Comment #1 from jwakely dot gcc at gmail dot com  2010-01-14 12:36 -------
(In reply to comment #0)

>     vec_t tmp2 = {};      // Causes warnings about uninitialized members in
> myvec

The warning doesn't smean it's uninitialized, just that there are not
initializers present for all members:

       -Wmissing-field-initializers
           Warn if a structure's initializer has some fields missing.  For
example, the following code would cause such a warning, because "x.h" is
implicitly
           zero:

                   struct s { int f, g, h; };
                   struct s x = { 3, 4 };

You can disable that with -Wno-missing-field-initializers (but that doesn't
help for cases where vec_t cannot be aggregate initialized)


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42743