We used to run them, but not check if they failed. If they do,
the expression is invalid, even if we already have a result.
I do have a suspicion that we need to manually call destroyLocals()
in more places (everywhere basically?), but I'll wait with that
until I have a reproducer at hand.
This function tried to be smart about the dereferenced value,
but it ended up hurting more than it helped. At least in the current
state, where we still try get the correct output.
I might add something similar back later.
Some time ago, I did a similar patch for local variables.
Initializing global variables can fail as well:
```c++
constexpr int a = 1/0;
static_assert(a == 0);
```
... would succeed in the new interpreter, because we never saved the
fact that `a` has not been successfully initialized.
Add an `EvaluationResult` class. This contains the result either as a
`Pointer` or as a `APValue`.
This way, we can inspect the result of the evaluation and diagnose
problems with it (e.g. uninitialized fields in global initializers or
pointers pointing to things they shouldn't point to).
For this code:
struct O {
int &&j;
};
O o1(0);
The generated AST for the initializer of o1 is:
VarDecl 0x62100006ab08 <array.cpp:119:3, col:9> col:5 o1 'O':'O' parenlistinit
`-ExprWithCleanups 0x62100006b250 <col:7, col:9> 'O':'O'
`-CXXParenListInitExpr 0x62100006b210 <col:7, col:9> 'O':'O'
`-MaterializeTemporaryExpr 0x62100006b1f0 <col:8> 'int' xvalue
`-IntegerLiteral 0x62100006abd0 <col:8> 'int' 0
Before this patch, we create a local temporary variable for the
MaterializeTemporaryExpr and destroy it again when destroying the
EvalEmitter we create to interpret the initializer. However, since
O::j is a reference, this reference now points to a local variable
that doesn't exist anymore.
Differential Revision: https://reviews.llvm.org/D156453
We can implement these similarly to DerivedToBase casts. We just have to
walk the class hierarchy, sum the base offsets and subtract it from the
current base offset of the pointer.
Differential Revision: https://reviews.llvm.org/D149133
Before this patch, we had visitRecordInitializer() and
visitArrayInitializer(), which were different from the regular visit()
in that they expected a pointer on the top of the stack, which they
initialized. For example, visitArrayInitializer handled InitListExprs by
looping over the members and initializing the elements of that pointer.
However, this had a few corner cases and problems. For example, in
visitLambdaExpr() (a lambda is always of record type), it was not clear
whether we should always create a new local variable to save the lambda
to, or not. This is why https://reviews.llvm.org/D153616 changed
things around.
This patch changes the visiting functions to:
- visit(): Always leaves a new value on the stack. If the expression
can be mapped to a primitive type, it's just visited and the value is
put on the stack. If it's of composite type, this function will
create a local variable for the expression value and call
visitInitializer(). The pointer to the local variable will stay on
the stack.
- visitInitializer(): Visits the given expression, assuming there is a
pointer on top of the stack that will be initialized by it.
- discard(): Visit the expression for side-effects, but don't leave a
value on the stack.
It also adds an additional Initializing flag to differentiate between the initializing and non-initializing case.
Differential Revision: https://reviews.llvm.org/D156027
We will use this opcode for conditionally executed statements that are
invalid in a constant expression.
Differential Revision: https://reviews.llvm.org/D150364
