Backport "[analyzer] Fix inf recursion in StackAddrEscapeChecker for self referencing blocks" #11905
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…encing blocks (llvm#169208) Objective-C blocks are like lambdas. They have captures, just like lambdas. However, they can also implicitly capture themselves unlike lambdas. This means that when walking the captures of a block, we may end up in infinite recursion. This is not possible with lambdas, but happened in practice with blocks downstream. In this patch, I just use a set to keep track of the visited MemRegions. Note that theoretically, there is nothing preventing usual lambdas or functors from falling for the same trap, but probably slightly more difficult to do so. You would likely need a pointer to itself, etc. I'll not speculate here. This inf recursion was likely caused by llvm#126620, released in clang-21. rdar://162215172 (cherry picked from commit 30b1d14)
ziqingluo-90
approved these changes
Dec 2, 2025
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@ziqingluo-90 Any testing needed? I saw on one of your previous PRs that you issued commands. |
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@swift-ci test llvm |
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Author
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@swift-ci test linux |
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@swift-ci test macOS |
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Objective-C blocks are like lambdas. They have captures, just like lambdas. However, they can also implicitly capture themselves unlike lambdas.
This means that when walking the captures of a block, we may end up in infinite recursion. This is not possible with lambdas, but happened in practice with blocks downstream.
In this patch, I just use a set to keep track of the visited MemRegions.
Note that theoretically, there is nothing preventing usual lambdas or functors from falling for the same trap, but probably slightly more difficult to do so. You would likely need a pointer to itself, etc. I'll not speculate here.
This inf recursion was likely caused by llvm#126620, released in clang-21.
rdar://162215172
(cherry picked from commit 30b1d14)