Hello,
In a number of places, the gimplifier simply discards what involves
zero sized entities. For instance:
in "gimplify_init_ctor_eval"...
FOR_EACH_CONSTRUCTOR_ELT (elts, ix, purpose, value)
...
if (zero_sized_field_decl (purpose))
continue;
or in "gimplify_modify_expr"...
/* For zero sized types only gimplify the left hand side and
right hand side as statements and throw away the assignment. */
if (zero_sized_type (TREE_TYPE (*from_p)))
...
This is causing troubles when side effects are so discarded, for instance
a call to a function returning a zero sized type.
I have been experimenting with a simple patch adding side effects
checks to the conditions, like "! TREE_SIDE_EFFECTS (value)" in
init_ctor_eval and "! TREE_SIDE_EFFECTS (*from_p)" in modify_expr.
The first programs in which I've observed problems were in Ada, and
the patch helped them.
Manual testing for C was not as successful (expected calls still
missing), due to differences in the way TREE_SIDE_EFFECTS is set on
various trees.
Automated testing (make check) even triggered an ICE on zero-strct-4.c.
Are the TREE_SIDE_EFFECTS checks mentioned above sensible ?
I'd be happy to investigate further, provide testcases, work on extra
patches, etc, and would welcome feedback first to ensure I'm searching
in the right direction :)
Thanks in advance for your advices,
With Kind Regards,
Olivier
