Hello cfe-users,
I'm working to get my the libobjc2 Objective-C runtime working on Linux with
clang-3.8.0. I'm running into a problem with a library of mine that does class
introspection. My ObjC code does type introspection by looping through the
ivars of an object and calling ivar_getTypeEncoding on each to get the type of
the ivar. When I compile with gcc, the ivar type for non-primitive variables
comes through as @"NSString", @"NSDictionary", etc. This also works with clang
on my Mac. But when I compile with clang on Linux, I only get the @ character.
I verified that the call to class_copyIvarList on Linux does return a list of
Ivar objects, but when I call ivar_getTypeEncoding on those objects on Linux, I
only get @, rather than the class name. I've copied my library's ObjC code
below.
I talked this over with the owners of libobjc2, and we were wondering if there
is a flag I can pass to clang to instruct it to emit this class data. I looked
at lib/CodeGen/CGObjCGNU.cpp in the clang source tree, but it wasn't
immediately clear what flag I could pass here. It's possible that there's no
such flag, and the non-Apple clang simply doesn't emit this data, but I'd be
somewhat surprised if Apple had diverged that much.
Thanks in advance for any help you can give,
David
My library's introspection code, with a debug print statement:
Ivar *ivarList = class_copyIvarList(c, &ivarCount);
for (i = 0; i < ivarCount; i++) {
Ivar ivar = ivarList[i];
const char *ivarCname = ivar_getName(ivar);
if (ivarCname != 0 && ivarCname[0] != '_') {
NSString *ivarName = [NSString stringWithUTF8String:ivarCname];
const char *ivarType = ivar_getTypeEncoding(ivar);
if (ivarType[0] == '@' && ivarType[1] == '"') {
NSString *className = [[[NSString alloc] initWithBytes: &ivarType[2]
length: strlen(&ivarType[2])-1
encoding: NSUTF8StringEncoding] autorelease];
Class c = NSClassFromString(className);
if (c == nil) {
NSLog(@"WARNING: unknown class name \"%@\" in declaration of %@",
className, [self class]);
} else {
NSLog(@"DBG: Deduced class %@ from className %@", c, className);
With gcc and clang on the Mac, I get messages like this:
2016-09-14 19:29:21.950 archiveserver[1015:1015] DBG: Deduced class NSSet from
className NSSet
2016-09-14 19:29:21.950 archiveserver[1015:1015] DBG: Deduced class NSString
from className NSString
2016-09-14 19:29:21.950 archiveserver[1015:1015] DBG: Deduced class NSString
from className NSString
2016-09-14 19:29:21.950 archiveserver[1015:1015] DBG: Deduced class NSString
from className NSString
2016-09-14 19:29:21.950 archiveserver[1015:1015] DBG: Deduced class
NSDictionary from className NSDictionary
2016-09-14 19:29:21.950 archiveserver[1015:1015] DBG: Deduced class
NSDictionary from className NSDictionary
2016-09-14 19:29:21.950 archiveserver[1015:1015] DBG: Deduced class NSArray
from className NSArray
With clang on Linux, nothing is printed, because ivarType[1] is not a double
quote, so the second if evaluates to false.
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