[Bug c/12391] New: regression: missing warning about assigning to an incomplete type

["levon at movementarian dot org" <gcc-bugzilla at gcc dot gnu dot org>]

PLEASE REPLY TO gcc-bugzilla@gcc.gnu.org ONLY, *NOT* gcc-bugs@gcc.gnu.org.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12391

           Summary: regression: missing warning about assigning to an
                    incomplete  type
           Product: gcc
           Version: 3.4
            Status: UNCONFIRMED
          Severity: minor
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: levon at movementarian dot org
                CC: gcc-bugs at gcc dot gnu dot org

Consider:

typedef struct { int a; } b_t;
int foo() { b_t d; struct b_t * c = &d; c->a; }

gcc 3.2 says :

a.c: In function `foo':
a.c:2: warning: initialization from incompatible pointer type
a.c:2: dereferencing pointer to incomplete type

GNU C version 3.4 20030914 (experimental) (i686-pc-linux-gnu) says :

a.c: In function `foo':
a.c:2: error: dereferencing pointer to incomplete type

Note the missing warning on initialisation. This can be moderately confusing
because the latter looks exactly like a "missing header" problem, but in fact
the problem is prepending the "struct" before the typedef name, which is
actually an incomplete type of "struct b_t".

The missing warning makes it obvious that it's not as simple as a missing
header.