On 09/23/2016 12:00 PM, Jason Merrill wrote:
On Thu, Sep 22, 2016 at 7:39 PM, Martin Sebor <mse...@gmail.com> wrote:
On 09/21/2016 02:43 PM, Jason Merrill wrote:
On Tue, Sep 20, 2016 at 1:01 PM, Martin Sebor <mse...@gmail.com> wrote:
On 09/16/2016 12:19 PM, Jason Merrill wrote:
On 09/14/2016 01:03 PM, Martin Sebor wrote:
+ /* Type of the member. */
+ tree fldtype = TREE_CODE (fld) == FIELD_DECL ? TREE_TYPE (fld) : fld;
Why set "fldtype" to be a TYPE_DECL rather than its type?
I'm not sure I understand the question but (IIRC) the purpose of
this code is to detect invalid uses of flexible array members in
typedefs such as this:
struct S { typedef struct { int i, a[]; } X2 [2]; };
Sadly, it doesn't do anything for
struct X { int i, a[]; };
struct S { typedef struct X X2 [2]; };
The issue is I don't see anything that uses fldtype as a decl, and
it's strange to have a variable called "*type" that can either be a
type or a decl, which later code still assumes will be a type.
I suspect I'm simply looking at it from a different point of view.
The definition
tree fldtype = TREE_CODE (fld) == FIELD_DECL ? TREE_TYPE (fld) : fld
denotes the type of the field if fld is a data member. Otherwise,
it denotes a type (like a typedef).
FLD is always a _DECL. The result of this assignment is that fldtype
refers to either a _TYPE or a _DECL. This creates a strange
asymmetry, and none of the following code seems to depend on it.
I would prefer
tree fldtype = TREE_TYPE (fld);
so that it's always a _TYPE.
I mentioned that this code is important to avoid diagnosing typedefs,
but the example I showed wasn't the right one. The examples that do
depend on it are these two:
struct S1 {
typedef int A [0];
A a;
};
struct S2 {
typedef struct { int i, a[]; } A1;
typedef struct { int i, a[]; } A2;
};
The expected (pedantic) warning is:
warning: zero-size array member ‘S1::a’ in an otherwise empty ‘struct
S1’
With the change you're asking we end up with:
warning: zero-size array member ‘S1::a’ not at end of ‘struct S1’
followed by a bogus
error: flexible array member ‘S2::A1::a’ not at end of ‘struct S2’
So I still don't understand what you're looking for. It sounds to
me like you're asking me to rewrite the subsequent code that uses
fldtype to use the expression above because you don't like that
fldtype can be either a _DECL or _TYPE. But repeating that check
four times doesn't make sense, so what am I missing?
My point is that for
struct X { int n, a[]; };
struct X2 { struct { int n, a[]; }; };
struct Y { int n, b[]; };
struct D: X, Y { };
struct D2: X2, Y { };
We say
wa3.C:1:21: error: flexible array member ‘X::a’ not at end of ‘struct D’
wa3.C:2:31: error: flexible array member ‘X2::<unnamed struct>::a’ not
at end of ‘struct X2’
If we want to say "struct D", why don't we also want to say "struct
D2"? It seems that you could unconditionally set fmemctx to t and not
bother calling anon_context.
I see. It looks like it doesn't matter anymore. I suspect the
whole anon_context business became unnecessary with the removal
of the overlapping union member code. I've removed the code and
added a test case to verify that the error references the same
parent class in both cases.
Martin
