https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95848
--- Comment #4 from Martin Sebor <msebor at gcc dot gnu.org> ---
There's no code code to handle the last case. The first case is handled
because the local s is assigned to a temporary and there is code to detect
uninitialized sources of assignments. The second case is handled in the new
maybe_warn_pass_by_reference() function. The third case enters the function
but is excluded because the argument is passed by value and nothing else checks
passing non-SSA_NAME operands.
In the test case below passing the uninitialized i is diagnosed because i's an
SSA_NAME. Passing s isn't because it's not one.
maybe_warn_pass_by_reference() should handle this case as well (and be renamed
appropriately).
$ gcc -S -Wall -fdump-tree-ssa=/dev/stdout ../t.c
;; Function h (h, funcdef_no=0, decl_uid=1948, cgraph_uid=1, symbol_order=0)
void h ()
{
int i;
struct S s;
<bb 2> :
fs (s, i_2(D));
s ={v} {CLOBBER};
return;
}
../t.c: In function ‘h’:
../t.c:9:3: warning: ‘i’ is used uninitialized [-Wuninitialized]
9 | fs (s, i);
| ^~~~~~~~~
