Add two commands pproperties, pblock

[longv2go]

pproperties can print the properties of an instance of Class.

(lldb) ppro self
@property (nonatomic, assign, readonly) NSString * helo;
@property (nonatomic, strong) NSNumber * number;

pblock can print the implementation address and signature of a block.

(lldb) pbl block
Imp: 0x101180980    Signature: void ^(NSString *);

[kastiglione]

Thank you. I'm hoping to review this before the end of the week.

[kastiglione]

@longv2go What do you think of looking up the symbol that corresponds to the block's invoke function, using something like image lookup --address or via the equivalent lldb api? Another thought to put out there, what do you think of print the objects that the block captures?

[longv2go]

@kastiglione The pblock just show the invoke function`s address, and I do not know which lldb api can do that. I can go deep with the block struct to find out if I can print the objects that the block captures.

[kastiglione]

I'm also not sure which part of the lldb api we're looking for, but worst case scenario we could call HandleCommand and pass it image lookup --address with the address of the invoke function pointer.

The two suggestions were just for discussion, they actually came up today when I was showing chisel to someone. They asked about inspecting blocks and I remembered this pull request (sorry). If adding symbol lookup isn't much work, which I hope is the case, then I think it's a no brainer to add. However I suspect getting the captured objects is more work and I also don't think it's as valuable as the symbol lookup. Those are my thoughts.

thanks!

[kastiglione]

props does not ever get freed.

[longv2go]

@kastiglione I remove the "free()" because it would cause evaluateExpressionValue to raise exception some time on real device. I do not know the reason. I guess it`s a lldb bug.

[longv2go]

@kastiglione The block struct is dynamically generated by the compiler. The captured objects and other objects the block referenced are all attached to that struct, such as

struct __block_literal_2 {
    void *isa;
    int flags;
    int reserved;
    void (*invoke)(struct __block_literal_2 *);
    struct __block_descriptor_2 *descriptor;
    const int x;
};

The const int x; is an object referenced by block. So every block is different. I did not find a way to list all captured objects at the runtime.

http://clang.llvm.org/docs/Block-ABI-Apple.html#importing-attribute-nsobject-variables

[kastiglione]

Thanks @longv2go. I'll give this another review today or tomorrow.

[kastiglione]

I remove the free() because it would cause evaluateExpressionValue to raise exception some time on real device.

@longv2go Do you have any more details on this? I guess it doesn't matter if a bit of memory leaks in debugging, but if it is an lldb bug, we might want to report it or track it if it's known.

[longv2go]

@kastiglione When I add the free(), I get the error message:

error: Execution was interrupted, reason: EXC_BAD_ACCESS (code=257, address=0x188ae089d).
The process has been returned to the state before expression evaluation.
error: Execution was interrupted, reason: EXC_BAD_ACCESS (code=257, address=0x188ae089d).
The process has been returned to the state before expression evaluation.
Traceback (most recent call last):
  File "/Users/didi/Workspace/github/chisel/fblldb.py", line 79, in runCommand
    command.run(args, options)
  File "/Users/didi/Workspace/github/chisel/commands/FBClassDump.py", line 84, in run
    printProperties(cls)
  File "/Users/didi/Workspace/github/chisel/commands/FBClassDump.py", line 195, in printProperties
    props = getProperties(cls)
  File "/Users/didi/Workspace/github/chisel/commands/FBClassDump.py", line 336, in getProperties
    return [Property(m) for m in propsJson]
TypeError: 'NoneType' object is not iterable

and the fb.evaluate(command) get a None.

[kastiglione]

Thanks. Would you mind putting that into a gist, and adding a comment with a link where the free go? If you're busy don't worry, we can refer back to this pull request.

[longv2go]

@kastiglione I create a new repo. I find a way to print all objects of a block using fishhook. Because the evaluateExpression function can not define a c function, I could`t implement chisel command to print those objects. Please refer https://github.com/longv2go/BlockInspector

[kastiglione]

@longv2go Does your new repo supersede this pull request? Should I still consider merging this, or should people instead use your BlockInspector?

[longv2go]

@kastiglione the repo BlockInspector is written in Objective-C, It can not implement as a chisel command.

[kastiglione]

@longv2go Understood. Would you like to continue with this pull request? Or do you plan to use BlockInspector instead?

[longv2go]

@kastiglione continue this pull request.

[kastiglione]

Thanks again!