While expression symbols worked for what they are, they weren't so good
for ivar access because every ivar of a class (and its super classes)
would be accessed at method scope creation, generating spurious access
errors if any were private. That is, when the access checks worked at
all.
The end goal was to fix erroneous non-constant initializer errors for
the following (ie, nested initializer blocks):
typedef struct { int x; int y; } Point;
typedef struct { int width; int height; } Extent;
typedef struct Rect_s { Point offset; Extent extent; } Rect;
Rect makeRect (int xpos, int ypos, int xlen, int ylen)
{
Rect rect = {{xpos, ypos}, {xlen, ylen}};
return rect;
}
However, it turned out that nested initializer blocks for local
variables did not work at all in that the relocations were lost because
fake defs were being created for the generated instructions.
Thus, instead of creating fake defs, simply record the offset relative
to the base def, the type, and the basic type initializer expression,
then generate instructions that all refer to the correct def but with a
relative offset.
Other than using the new element system, static initializers are largely
unaffected.
This is for adding methods to classes and protocols via their interface,
not for adding methods by adding protocols (they still get copied).
Slightly more memory efficient.
Copying methods is done when adding protocols to classes (the current
use for adding regular methods is an incorrect solution to a different
problem). However, when a method is added to a class, the type of its
self parameter is set to be a pointer to the class. Thus, not only does
the method need to be copied, the self parameter does too, otherwise
the self parameter of methods added via protocols will have their type
set to be a pointer to the last class seen adding the protocol.
That is, if, while compiling the implementation for class A, but the
interface for class B is comes after the interface for class A, and both
A and B add protocol P, then all methods in protocol P will have self
pointing to B rather than A.
@protocol P
-method;
@end
@interface A <P>
@end
@interface B <P>
@end
@implementation A
-method {} // self is B, not A!
@end
Duplicate methods in an interface (especially across protocols and
between protocols and the interface) are both harmless and even to be
expected. They certainly should not cause the compiler to demand
duplicate method implementations :)
This is actually a double issue: when a class implementing a protocol
used the protocol in @protocol(), not only would the protocol get
emitted as part of the class data specifying that the class conforms to
the protocol, a second instance would be emitted again when @protocol()
was used. On top of that, only the instance referenced by @protocol()
would be initialized. Now, both class emission and @protocol() get their
protocol def from the same place and thus only one, properly
initialized, protocol instance is emitted.
The problem was an erroneous assumption that the methods had to be
defined. Any class implementing a protocol must implement (and thus
define) the methods, but a protocol declaration cannot: it merely
declares the methods, and it's entirely possible for a module to see
only the protocol definition and not any classes implementing the
protocol.
Unlike gcc, qfcc requires foo to be defined, not just declared (I
suspect this is a bug in gcc, or even the ObjC spec), because allowing
forward declarations causes an empty (no methods) protocol to be
emitted, and then when the protocol is actually defined, one with
methods, resulting in two different versions of the same protocol, which
comments in the gnu objc runtime specifically state is a problem but is
not checked because it "never happens in practice" (found while
investigating gcc's behavior with @protocol and just what some of the
comments about static instance lists meant).
It proved to be too fragile in its current implementation. It broke
pointers to incomplete structs and switch enum checking, and getting it
to work for other things was overly invasive. I still want the encoding,
but need to come up with something more robust.a
Such declarations were being lost, thus in the following, the id field
never got added:
typedef struct qwaq_mevent_s {
int id;
int x, y, z;
int buttons;
} qwaq_mevent_t;
