| Issue |
76472
|
| Summary |
[libclang] `annotateTokens()` produces different cursor than `visitChildren()`
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
jimmy-zx
|
While testing the `annotateTokens()` function (used by `Token.cursor` of the python binding), I found that for some cursor, the (only) token that belongs to that cursor does not maps back to the cursor itself.
For example, on the following code,
```c
struct a {
int b;
};
int func(struct a *ptr) {
int r = ptr->b;
return r;
}
```
I made a script that selects the `DeclRefExpr` that refers `ptr` in the statement `int r = ptr->b`, and check if the only token that belongs to the _expression_, `ptr`'s cursor maps to the cursor.
```python
from clang.cindex import TranslationUnit, Cursor, CursorKind
def main():
tu = TranslationUnit.from_source("./demo.c")
root: Cursor = tu.cursor
node = None
for node in root.walk_preorder():
if node.kind == CursorKind.DECL_REF_EXPR and node.spelling == "ptr":
break
token = None
for token in node.get_tokens():
break
print(token.cursor == node)
print(token.cursor._kind_id, node._kind_id)
print(token.cursor.xdata, node.xdata)
print(*token.cursor.data)
print(*node.data)
if __name__ == '__main__':
main()
```
The result of the above script is
```
False
101 101
0 0
140162768666120 140162768666224 140162768050240
None 140162768666224 140162768050240
```
The cursors `node` and `token.cursor` should be the same, and they indeed share the same spelling and extent. However, `libclang` consider them as different cursors.
The equality of cursor is provided by `clang_equalCursors()`, and the only difference between these two cursors are `data[0]`.
https://github.com/llvm/llvm-project/blob/1c1eaf75f5f2efd72ba813b29b3d7b556d61b70b/clang/tools/libclang/CIndex.cpp#L6289-L6303
I suspect that the creation for `DeclRefExpr` cursors are in `MakeCXCursor()`, and `data[0]` probably means the parent cursor.
https://github.com/llvm/llvm-project/blob/1c1eaf75f5f2efd72ba813b29b3d7b556d61b70b/clang/tools/libclang/CXCursor.cpp#L570-L583
https://github.com/llvm/llvm-project/blob/1c1eaf75f5f2efd72ba813b29b3d7b556d61b70b/clang/tools/libclang/CXCursor.cpp#L876-L878
There might be an issue where the `data[0]` (parent) field is not being set properly, or `clang_equalCursors()` should ignore `data[0]` when comparing statements?
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