Szelethus marked an inline comment as done.
Szelethus added inline comments.
================
Comment at: clang/lib/Analysis/LiveVariables.cpp:317-320
for (Stmt *Child : S->children()) {
- if (Child)
- AddLiveStmt(val.liveStmts, LV.SSetFact, Child);
+ if (const auto *E = dyn_cast_or_null<Expr>(Child))
+ AddLiveExpr(val.liveExprs, LV.SSetFact, E);
}
----------------
xazax.hun wrote:
> Szelethus wrote:
> > ..this part of the code caused the issue. Looking at the related CFG,
> > ```lang=c++
> > void test_lambda_refcapture()
> > [B2 (ENTRY)]
> > Succs (1): B1
> >
> > [B1]
> > 1: 6
> > 2: int a = 6;
> > 3: operator()
> > 4: [B1.3] (ImplicitCastExpr, FunctionToPointerDecay, void (*)(int &)
> > const)
> > 5: [&](int &a) {
> > a = 42;
> > }
> > 6: [B1.5]
> > 7: [B1.6] (ImplicitCastExpr, NoOp, const class (lambda at
> > /home/szelethus/Documents/llvm-project/clang/test/Analysis/live-stmts.cpp:183:3))
> > 8: a
> > 9: [B1.7]([B1.8]) (OperatorCall)
> > 10: clang_analyzer_eval
> > 11: [B1.10] (ImplicitCastExpr, FunctionToPointerDecay, void (*)(_Bool))
> > 12: a
> > 13: [B1.12] (ImplicitCastExpr, LValueToRValue, int)
> > 14: 42
> > 15: [B1.13] == [B1.14]
> > 16: [B1.11]([B1.15])
> > Preds (1): B2
> > Succs (1): B0
> >
> > [B0 (EXIT)]
> > Preds (1): B1
> > ```
> > its clear that element 5 added the live statement, and I think that that
> > this entire CFG just simply isn't right. Shouldn't we have a distinct
> > element for the assignment?
> >
> > Shouldn't we have a distinct element for the assignment?
>
> Strictly speaking, we have CFGs for a function. The assignment is **not** in
> this function, it is in the `operator()` of the class representing this
> lambda expression.
>
> So basically, we do have a `LambdaExpr` to represent the expression, but the
> body of the lambda is in a separate entity.
Well, `debug.DumpCFG` definitely doesn't indulge me with a separate lambda CFG,
so I figured this is a (rightful) optimization or compression.
My point is, this entire code snippet is a seriously error prone, best-effort
heuristic. Switch casing every small little corner case might be tedious,
troublesome in terms of scaling, and I for sure don't want to maintain it 'til
eternity, but we have to acknowledge that this isn't a perfect solution either.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D82598/new/
https://reviews.llvm.org/D82598
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