7fbd427f5e
Add the ability to get a C++ vtable ValueObject from another
ValueObject.
This patch adds the ability to ask a ValueObject for a ValueObject that
represents the virtual function table for a C++ class. If the
ValueObject is not a C++ class with a vtable, a valid ValueObject value
will be returned that contains an appropriate error. If it is successful
a valid ValueObject that represents vtable will be returned. The
ValueObject that is returned will have a name that matches the demangled
value for a C++ vtable mangled name like "vtable for <class-name>". It
will have N children, one for each virtual function pointer. Each
child's value is the function pointer itself, the summary is the
symbolication of this function pointer, and the type will be a valid
function pointer from the debug info if there is debug information
corresponding to the virtual function pointer.
The vtable SBValue will have the following:
- SBValue::GetName() returns "vtable for <class>"
- SBValue::GetValue() returns a string representation of the vtable
address
- SBValue::GetSummary() returns NULL
- SBValue::GetType() returns a type appropriate for a uintptr_t type for
the current process
- SBValue::GetLoadAddress() returns the address of the vtable adderess
- SBValue::GetValueAsUnsigned(...) returns the vtable address
- SBValue::GetNumChildren() returns the number of virtual function
pointers in the vtable
- SBValue::GetChildAtIndex(...) returns a SBValue that represents a
virtual function pointer
The child SBValue objects that represent a virtual function pointer has
the following values:
- SBValue::GetName() returns "[%u]" where %u is the vtable function
pointer index
- SBValue::GetValue() returns a string representation of the virtual
function pointer
- SBValue::GetSummary() returns a symbolicated respresentation of the
virtual function pointer
- SBValue::GetType() returns the function prototype type if there is
debug info, or a generic funtion prototype if there is no debug info
- SBValue::GetLoadAddress() returns the address of the virtual function
pointer
- SBValue::GetValueAsUnsigned(...) returns the virtual function pointer
- SBValue::GetNumChildren() returns 0
- SBValue::GetChildAtIndex(...) returns invalid SBValue for any index
Examples of using this API via python:
```
(lldb) script vtable = lldb.frame.FindVariable("shape_ptr").GetVTable()
(lldb) script vtable
vtable for Shape = 0x0000000100004088 {
[0] = 0x0000000100003d20 a.out`Shape::~Shape() at main.cpp:3
[1] = 0x0000000100003e4c a.out`Shape::~Shape() at main.cpp:3
[2] = 0x0000000100003e7c a.out`Shape::area() at main.cpp:4
[3] = 0x0000000100003e3c a.out`Shape::optional() at main.cpp:7
}
(lldb) script c = vtable.GetChildAtIndex(0)
(lldb) script c
(void ()) [0] = 0x0000000100003d20 a.out`Shape::~Shape() at main.cpp:3
```
39 lines
1.1 KiB
C++
39 lines
1.1 KiB
C++
class Shape {
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public:
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virtual double Area() { return 1.0; }
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virtual double Perimeter() { return 1.0; }
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// Note that destructors generate two entries in the vtable: base object
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// destructor and deleting destructor.
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virtual ~Shape() = default;
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};
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class Rectangle : public Shape {
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public:
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~Rectangle() override = default;
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double Area() override { return 2.0; }
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double Perimeter() override { return 2.0; }
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virtual void RectangleOnly() {}
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// This *shouldn't* show up in the vtable.
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void RectangleSpecific() { return; }
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};
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// Make a class that looks like it would be virtual because the first ivar is
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// a virtual class and if we inspect memory at the address of this class it
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// would appear to be a virtual class. We need to make sure we don't get a
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// valid vtable from this object.
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class NotVirtual {
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Rectangle m_rect;
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public:
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NotVirtual() = default;
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};
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int main(int argc, const char **argv) {
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Shape shape;
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Rectangle rect;
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Shape *shape_ptr = ▭
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Shape &shape_ref = shape;
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shape_ptr = &shape; // Shape is Rectangle
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NotVirtual not_virtual; // Shape is Shape
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return 0; // At the end
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}
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