On 3/15/22 12:06, Jakub Jelinek wrote:
On Tue, Mar 15, 2022 at 11:57:22AM -0400, Jason Merrill wrote:
The intent of r11-6729 is that it prints something that helps user to figure
out what exactly is being accessed.
When we find a unique non-static data member that is being accessed, even
when we can't fold it nicely, IMNSHO it is better to print
((sometype *)&var)->field
or
(*(sometype *)&var).field
instead of
*(fieldtype *)((char *)&var + 56)
because the user doesn't know what is at offset 56, we shouldn't ask user
to decipher structure layout etc.
The problem is that the reference is *not* to any non-static data member,
it's to the PMF as a whole. But c_fold_indirect_ref_for_warn wrongly turns
it into a reference to the first non-static data member.
We asked c_fold_indirect_ref_warn to fold a MEM_REF with RECORD_TYPE, and it
gave us back a COMPONENT_REF with POINTER_TYPE. That seems clearly wrong.
That is not what I see on the testcase.
I see the outer c_fold_indirect_ref_for_warn call with type ptrmemfunc
which is a 64-bit RECORD_TYPE containing a single ptr member which has
pointer to function type, and op which is the x VAR_DECL with sp type which
is 128-bit RECORD_TYPE containing 64-bit __pfn member and 64-bit __delta
member.
Exactly: TYPE is RECORD_TYPE, TREE_TYPE (field) is POINTER_TYPE.
As all the bits of the ptrmemfunc RECORD_TYPE fit within the __pfn member
(they are equal size), it wants to print (cast)(something.__pfn).
I disagree that this is what we want; we asked to fold an expression
with class type, it seems unlikely that we want to get back an
expression with pointer type.
Jason
