| Issue |
136135
|
| Summary |
[clang][bytecode] Find a way around `PointerToIntegral` cast that result in an lvalue
|
| Labels |
clang:frontend,
clang:bytecode
|
| Assignees |
|
| Reporter |
tbaederr
|
Consider this simple example:
```c
typedef __typeof((int*) 0 - (int*) 0) intptr_t;
int a = 10;
intptr_t s = (intptr_t) &a;
```
Comipiled as C, there are no compilation errors. However, when evaluating the initializer for `s`:
```
CStyleCastExpr 0x7d6799454e40 'intptr_t':'long' <PointerToIntegral>
`-UnaryOperator 0x7d6799454e08 'int *' prefix '&' cannot overflow
`-DeclRefExpr 0x7d6799454de0 'int' lvalue Var 0x7d6799454bf8 'a' 'int'
```
the current interpreter doesn't actually return an integer value at all, it returns an lvalue pointing to `a`:
```
LValue Base=VarDecl 0x7d6799454bf8, Null=0, Offset=0, HasPath=0
```
which ultimately means we get the following IR:
```llvm
@a = dso_local global i32 10, align 4
@s = dso_local global i64 ptrtoint (ptr @a to i64), align 8
```
that's because the current interpreter takes this code path:
https://github.com/llvm/llvm-project/blob/fb00fa56b51b191d026eec104905e416bf34bbda/clang/lib/AST/ExprConstant.cpp#L15269-L15280
which means it returns an lvalue from an AST node that returns an integer. That works in the current interpreter where everything is an `APValue` an one can check the type of those values, but in a bytecode interpreter, where we expect the computed type to match the node type, it doesn't work.
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