explictly handle UB inputs in __divti3 and __modti3

AntelopeIO · Aug 27, 2024 · 473d562 · 473d562
1 parent be2cc9c
commit 473d562
Showing 1 changed file with 12 additions and 0 deletions.
diff --git a/libraries/chain/webassembly/compiler_builtins.cpp b/libraries/chain/webassembly/compiler_builtins.cpp
@@ -45,6 +45,12 @@ namespace eosio { namespace chain { namespace webassembly {
 
       EOS_ASSERT(rhs != 0, arithmetic_exception, "divide by zero");
 
+      //force integer overflow to return dividend unchanged
+      if(lhs == std::numeric_limits<__int128>::min() && rhs == -1) {
+         *ret = lhs;
+         return;
+      }
+
       lhs /= rhs;
 
       *ret = lhs;
@@ -92,6 +98,12 @@ namespace eosio { namespace chain { namespace webassembly {
 
       EOS_ASSERT(rhs != 0, arithmetic_exception, "divide by zero");
 
+      //force undefined behavior (due to lhs/rhs being an overflow) to return zero
+      if(lhs == std::numeric_limits<__int128>::min() && rhs == -1) {
+         *ret = 0;
+         return;
+      }
+
       lhs %= rhs;
       *ret = lhs;
    }