Fix SafeHeap crash when start function calls an imported function#8306
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kripken merged 2 commits intoWebAssembly:mainfrom Feb 19, 2026
Merged
Fix SafeHeap crash when start function calls an imported function#8306kripken merged 2 commits intoWebAssembly:mainfrom
kripken merged 2 commits intoWebAssembly:mainfrom
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findCalledFunctions transitively walks all functions called from the start function to determine which functions should not be instrumented. When the start function calls an imported function, the import was added to the worklist and then FindAll<Call> was called on its null body, causing an assertion failure in the walker (assert(*currp) in wasm-traversal.h). Skip imported functions in the traversal since they have no body to walk.
kripken
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Feb 12, 2026
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Thanks, looks good aside from some test comments.
| @@ -0,0 +1,28 @@ | |||
| ;; NOTE: Assertions have been generated by update_lit_checks.py and should not be edited. | |||
| ;; RUN: wasm-opt %s --safe-heap --enable-threads --enable-simd -S -o - | filecheck %s | |||
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| ;; RUN: wasm-opt %s --safe-heap --enable-threads --enable-simd -S -o - | filecheck %s | |
| ;; RUN: wasm-opt %s --safe-heap -S -o - | filecheck %s |
These features are not used in the testcase.
| (import "env" "some_import" (func $import)) | ||
| ;; CHECK: (import "env" "emscripten_get_sbrk_ptr" (func $emscripten_get_sbrk_ptr (result i32))) | ||
| (import "env" "emscripten_get_sbrk_ptr" (func $emscripten_get_sbrk_ptr (result i32))) | ||
| (memory 1 1 shared) |
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| (memory 1 1 shared) | |
| (memory 1 1) |
No need for this to be shared.
| ;; CHECK: (import "env" "some_import" (func $import)) | ||
| (import "env" "some_import" (func $import)) | ||
| ;; CHECK: (import "env" "emscripten_get_sbrk_ptr" (func $emscripten_get_sbrk_ptr (result i32))) | ||
| (import "env" "emscripten_get_sbrk_ptr" (func $emscripten_get_sbrk_ptr (result i32))) |
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| (import "env" "emscripten_get_sbrk_ptr" (func $emscripten_get_sbrk_ptr (result i32))) |
No need for this import.
| (call $import) | ||
| ) | ||
|
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| (start $start) |
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By convention we put this before the first function (around line 16, here)
- Remove unused --enable-threads --enable-simd flags - Remove unnecessary emscripten_get_sbrk_ptr import - Remove unnecessary shared on memory - Move (start $start) before functions per convention
kripken
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Feb 19, 2026
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Summary
findCalledFunctionsin SafeHeap transitively walks all functions called from the start function to determine which functions should not be instrumented. When the start function calls an imported function, the import was added to the worklist and thenFindAll<Call>was called on its null body, causing an assertion failure in the walker:Reproducer:
Fix
Skip imported functions in the traversal since they have no body to walk.
Test plan
test/lit/passes/safe-heap-start-import.wastwith a start function that calls an import