Check permutation size before calling reserve() in WaksmanPermuterFor…

…BitString (#459)

Summary:
In T139444907 the NCC made us aware of the fact that an array of size 1 would cause the permuter to throw and exception. This is due to the bit size calculation for a single value permutation to return -1 as the required size.

Pull Request resolved: #459

Reviewed By: xyguo

Differential Revision: D42014844

fbshipit-source-id: 5f78009c9845204052b7c7f9da36518858aac839

fbpcf/mpc_std_lib/permuter/AsWaksmanPermuterForBitString_impl.h

@@ -111,7 +111,9 @@ AsWaksmanPermuter<std::vector<bool>, schedulerId>::permute(
   }
   auto length = vectorOfVectors.at(0).size();
   std::vector<std::vector<bool>> rst;
-  rst.reserve(2 * (std::ceil(log2(order.size()))) - 1);
+  if (order.size() > 2) {
+    rst.reserve(2 * (std::ceil(log2(order.size()))) - 1);
+  }
   computeChoiceVectors(
       std::vector<std::vector<uint32_t>>(1, order), rst, order.size());
 

fbpcf/mpc_std_lib/permuter/test/PermuterTest.cpp

@@ -74,12 +74,12 @@ void party1Task(
 
 void permuterTest(
     IPermuterFactory<frontend::BitString<true, 0, true>>& permuterFactory0,
-    IPermuterFactory<frontend::BitString<true, 1, true>>& permuterFactory1) {
+    IPermuterFactory<frontend::BitString<true, 1, true>>& permuterFactory1,
+    uint32_t size) {
   auto agentFactories = engine::communication::getInMemoryAgentFactory(2);
   setupRealBackend<0, 1>(*agentFactories[0], *agentFactories[1]);
   auto permuter0 = permuterFactory0.create();
   auto permuter1 = permuterFactory1.create();
-  uint32_t size = 17;
   auto [originalData, order, expectedOutput] = getPermuterTestData(size);
   auto future0 =
       std::async(party0Task, std::move(permuter0), originalData, order);
@@ -95,14 +95,21 @@ TEST(permuterTest, testDummyPermuter) {
   insecure::DummyPermuterFactory<std::vector<bool>, 0> factory0(0, 1);
   insecure::DummyPermuterFactory<std::vector<bool>, 1> factory1(1, 0);
 
-  permuterTest(factory0, factory1);
+  permuterTest(factory0, factory1, 17);
 }
 
 TEST(permuterTest, testAsWaksmanPermuter) {
   AsWaksmanPermuterFactory<std::vector<bool>, 0> factory0(0, 1);
   AsWaksmanPermuterFactory<std::vector<bool>, 1> factory1(1, 0);
 
-  permuterTest(factory0, factory1);
+  permuterTest(factory0, factory1, 17);
+}
+
+TEST(permuterTest, testAsWaksmanPermuterSingleValue) {
+  AsWaksmanPermuterFactory<std::vector<bool>, 0> factory0(0, 1);
+  AsWaksmanPermuterFactory<std::vector<bool>, 1> factory1(1, 0);
+
+  permuterTest(factory0, factory1, 1);
 }
 
 void testAsWaksmanParameter() {