[Relax] Fix segfault in rewrite_bindings for MatchCast node #17226
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Prior to this commit, the `tvm.relax.dpl.rewrite_bindings` utility would segfault if its input contained a `DataflowBlock` whose first binding was a `MatchCast`. The root cause is use of an unintialized `const VarNode* cur_user_;` when collecting the variable usage. This variable is only initialized for `VarBinding` nodes, and may be used uninitialized if a `MatchCast` node is encountered before the first `VarBinding`. This uninitialized value is later dereferenced during while pattern-matching, causing a segfault. This commit provides a default value of `nullptr` for `MatcherUseDefAnalysis::cur_user_`, preventing the segfault.
tqchen
approved these changes
Jul 31, 2024
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Prior to this commit, the
tvm.relax.dpl.rewrite_bindingsutility would segfault if its input contained aDataflowBlockwhose first binding was aMatchCast.The root cause is use of an unintialized
const VarNode* cur_user_;when collecting the variable usage. This variable is only initialized forVarBindingnodes, and may be used uninitialized if aMatchCastnode is encountered before the firstVarBinding. This uninitialized value is later dereferenced during while pattern-matching, causing a segfault.This commit provides a default value of
nullptrforMatcherUseDefAnalysis::cur_user_, preventing the segfault.