Description of problem:

Use of the '{0}' initializer on structure objects which have aggregate members
produces a warning when compiled with -Wextra.

Example:

file a.c :
<quote>
struct s { int a ; char *b; struct { float c; char d ; } e; char f ; };
typedef struct s t;
void f(void)
{
  t v={0};
}
</quote>

$ gcc -std=c99 -Wall -Wextra -c a.c
a.c: In function 'f':
a.c:5: warning: missing initializer
a.c:5: warning: (near initialization for 'v.b')
a.c:5: warning: unused variable 'v'

According to C99 (n1124.pdf), section 6.7.8 paragraph 21:
<quote>
If there are fewer initializers in a brace-enclosed list than there are 
elements or members of an aggregate, or fewer characters in a string literal
used to initialize an array of known size than there are elements in the array,
the remainder of the aggregate shall be initialized implicitly the same as
objects that have static storage duration.
</quote>

Indeed, gcc-4.8.x emits only the "unused variable 'v'" warning with the same
command line, so this appears to be fixed upstream.

Warning such as this get me worried - does the object truly contain an
uninitialized 'b' member, or is the warning bogus ?

Version-Release number of selected component (if applicable):

4.4.7-3

$ gcc -v | tail -n 1:
gcc version 4.4.7 20120313 (Red Hat 4.4.7-3) (GCC)


How reproducible:

100% 

Steps to Reproduce:
try to compile code containing a partial structure initializer of an 
object containing aggregate members

Actual results:
gcc emits 'missing initializer' warning with -Wextra.

Expected results:
gcc should be fully initializing the structure object's memory to all 0's and
not emitting a warning in this case, even with -Wextra.


Additional info: