[Clang] Expansion of pack indexing expression that is a pack in a lambda triggers ICE #91885
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clang:frontend
Language frontend issues, e.g. anything involving "Sema"
crash
Prefer [crash-on-valid] or [crash-on-invalid]
lambda
C++11 lambda expressions
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@llvm/issue-subscribers-clang-frontend Author: A. Jiang (frederick-vs-ja)
It seems that some branches are missing for this case. [Godbolt link](https://godbolt.org/z/8YK9MGYdb).
```C++
#include <cstddef>
#include <utility>
void operate_one(auto&&) {} void operate_multi(auto&&...args) int main() mangling a placeholder type
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After reducing this example I get another ICE with a different crash report: void ICE(auto...args){
[&]<int idx>(){
using R = decltype( args...[idx] ) ;
}.template operator()<0>();
}
int main( ) {
ICE(1);
}
See https://godbolt.org/z/Ge5cbEM7e. Shall I open a new issue? |
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It seems that the issue is related to the following function: llvm-project/clang/lib/AST/ComputeDependence.cpp Lines 367 to 380 in ad1a65f Let's consider the following code snippets: void ICE(auto...args){
[&]<int idx>(){
using R = decltype( args...[idx] ) ;
}.template operator()<0>();
}
int main( ) {
ICE(1);
}When the transformation of substituting the template parameters of function Currently:
That's wrong since actually,
Then in: llvm-project/clang/lib/Sema/SemaType.cpp Lines 9739 to 9748 in ad1a65f Since Possible fix: diff --git a/clang/lib/AST/ComputeDependence.cpp b/clang/lib/AST/ComputeDependence.cpp
index bad8e75b2f87..8d39431c889f 100644
--- a/clang/lib/AST/ComputeDependence.cpp
+++ b/clang/lib/AST/ComputeDependence.cpp
@@ -385,6 +385,10 @@ ExprDependence clang::computeDependence(PackIndexingExpr *E) {
std::optional<unsigned> Index = E->getSelectedIndex();
assert(Index && *Index < Exprs.size() && "pack index out of bound");
D |= Exprs[*Index]->getDependence();
+ } else {
+ /// non-empty PackIndexingExpr is type-dependent
+ /// if IndexExpr is instantiation-dependent
+ D |= ExprDependence::Type;
}
return D;
}
CC: @cor3ntin |
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@RungeCC Thanks, that was exactly the issue :) |
cor3ntin
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May 13, 2024
Given `foo...[idx]` if idx is value dependent, the expression is type dependent. Fixes llvm#91885 Fixes llvm#91884
cor3ntin
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Given `foo...[idx]` if idx is value dependent, the expression is type dependent. Fixes llvm#91885 Fixes llvm#91884
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mub-at-arm
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May 16, 2024
…#91933) Given `foo...[idx]` if idx is value dependent, the expression is type dependent. Fixes llvm#91885 Fixes llvm#91884
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It seems that some branches are missing for this case. Godbolt link.
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