[Bug c/38019] New: Cannot use nested designated initializer with unnamed inner aggregate

[josh at freedesktop dot org]

I have an aggregate with this definition:

typedef union vec3 {
        struct {
                double x, y, z;
        };
        double component[3];
} vec3;

Given this definition, I tried to write the following:

static inline vec3 vec_add(vec3 a, vec3 b)
{
        return (vec3) {
               .x = a.x + b.x,
               .y = a.y + b.y,
               .z = a.z + b.z,
        };
}

GCC complained about this:
vec.h: In function ‘vec_add’:
vec.h:15: error: missing braces around initializer
vec.h:15: error: (near initialization for ‘(anonymous).<anonymous>’)

If I had given the nameless inner struct a name, such as "foo", I could have
written:

static inline vec3 vec_add(vec3 a, vec3 b)
{
        return (vec3) {
               .foo.x = a.foo.x + b.foo.x,
               .foo.y = a.foo.y + b.foo.y,
               .foo.z = a.foo.z + b.foo.z,
        };
}

So since the inner struct does not have a name, it seems reasonable to allow a
designated initializer to omit the name.  GCC has no problem unambiguously
resolving the field reference a.x, so it seems like GCC should unambiguously
resolve the designated initializer .x = expression.


In case it helps:
$ gcc -v
Using built-in specs.
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 4.3.2-1'
--with-bugurl=file:///usr/share/doc/gcc-4.3/README.Bugs
--enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --enable-shared
--with-system-zlib --libexecdir=/usr/lib --without-included-gettext
--enable-threads=posix --enable-nls --with-gxx-include-dir=/usr/include/c++/4.3
--program-suffix=-4.3 --enable-clocale=gnu --enable-libstdcxx-debug
--enable-objc-gc --enable-mpfr --enable-cld --enable-checking=release
--build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 4.3.2 (Debian 4.3.2-1)


-- 
           Summary: Cannot use nested designated initializer with unnamed
                    inner aggregate
           Product: gcc
           Version: 4.3.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: josh at freedesktop dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38019