Address a couple of Coverity false positives

Add tests for is_power_of_2

4 files changed, 62 insertions, 7 deletions

diff --git a/src/lib/utils/bit_ops.h b/src/lib/utils/bit_ops.h
index d781d64d5..c6cce8ae2 100644
--- a/src/lib/utils/bit_ops.h
+++ b/src/lib/utils/bit_ops.h
@@ -24,7 +24,7 @@ namespace Botan {
 template<typename T>
 inline constexpr bool is_power_of_2(T arg)
    {
-   return ((arg != 0 && arg != 1) && ((arg & (arg-1)) == 0));
+   return ((arg != 0 && arg != 1) && ((arg & static_cast<T>(arg-1)) == 0));
    }
 
 /**
diff --git a/src/lib/utils/poly_dbl/poly_dbl.cpp b/src/lib/utils/poly_dbl/poly_dbl.cpp
index 65cee9f01..618fce202 100644
--- a/src/lib/utils/poly_dbl/poly_dbl.cpp
+++ b/src/lib/utils/poly_dbl/poly_dbl.cpp
@@ -35,8 +35,13 @@ void poly_double(uint8_t out[], const uint8_t in[])
    const uint64_t POLY = static_cast<uint64_t>(P);
 
    const uint64_t carry = POLY * (W[0] >> 63);
-   for(size_t i = 0; i != LIMBS - 1; ++i)
-      W[i] = (W[i] << 1) ^ (W[i+1] >> 63);
+
+   if(LIMBS > 0)
+      {
+      for(size_t i = 0; i != LIMBS - 1; ++i)
+         W[i] = (W[i] << 1) ^ (W[i+1] >> 63);
+      }
+
    W[LIMBS-1] = (W[LIMBS-1] << 1) ^ carry;
 
    copy_out_be(out, LIMBS*8, W);
@@ -51,8 +56,13 @@ void poly_double_le(uint8_t out[], const uint8_t in[])
    const uint64_t POLY = static_cast<uint64_t>(P);
 
    const uint64_t carry = POLY * (W[LIMBS-1] >> 63);
-   for(size_t i = 0; i != LIMBS - 1; ++i)
-      W[LIMBS-1-i] = (W[LIMBS-1-i] << 1) ^ (W[LIMBS-2-i] >> 63);
+
+   if(LIMBS > 0)
+      {
+      for(size_t i = 0; i != LIMBS - 1; ++i)
+         W[LIMBS-1-i] = (W[LIMBS-1-i] << 1) ^ (W[LIMBS-2-i] >> 63);
+      }
+
    W[0] = (W[0] << 1) ^ carry;
 
    copy_out_le(out, LIMBS*8, W);
diff --git a/src/tests/test_utils.cpp b/src/tests/test_utils.cpp
index 6708524b4..485d72a2a 100644
--- a/src/tests/test_utils.cpp
+++ b/src/tests/test_utils.cpp
@@ -1,5 +1,5 @@
 /*
-* (C) 2015 Jack Lloyd
+* (C) 2015,2018 Jack Lloyd
 * (C) 2016 Daniel Neus, Rohde & Schwarz Cybersecurity
 * (C) 2017 René Korthaus, Rohde & Schwarz Cybersecurity
 *
@@ -15,6 +15,7 @@
 #include <botan/calendar.h>
 #include <botan/internal/rounding.h>
 #include <botan/internal/ct_utils.h>
+#include <botan/internal/bit_ops.h>
 #include <botan/charset.h>
 #include <botan/parsing.h>
 #include <botan/version.h>
@@ -236,6 +237,51 @@ class CT_Mask_Tests final : public Test
 
 BOTAN_REGISTER_TEST("ct_utils", CT_Mask_Tests);
 
+class BitOps_Tests final : public Test
+   {
+   public:
+      std::vector<Test::Result> run() override
+         {
+         std::vector<Test::Result> results;
+
+         results.push_back(test_power_of_2());
+
+         return results;
+         }
+   private:
+      template<typename T>
+      void test_power_of_2(Test::Result& result, T val, bool expected)
+         {
+         result.test_eq("power_of_2(" + std::to_string(val) + ")", Botan::is_power_of_2<T>(val), expected);
+         }
+
+      Test::Result test_power_of_2()
+         {
+         Test::Result result("is_power_of_2");
+
+         test_power_of_2<uint32_t>(result, 0, false);
+         test_power_of_2<uint32_t>(result, 1, false);
+         test_power_of_2<uint32_t>(result, 2, true);
+         test_power_of_2<uint32_t>(result, 3, false);
+         test_power_of_2<uint32_t>(result, 0x8000, true);
+         test_power_of_2<uint32_t>(result, 0x8001, false);
+         test_power_of_2<uint32_t>(result, 0x8000000, true);
+
+         test_power_of_2<uint64_t>(result, 0, false);
+         test_power_of_2<uint64_t>(result, 1, false);
+         test_power_of_2<uint64_t>(result, 2, true);
+         test_power_of_2<uint64_t>(result, 3, false);
+         test_power_of_2<uint64_t>(result, 0x8000, true);
+         test_power_of_2<uint64_t>(result, 0x8001, false);
+         test_power_of_2<uint64_t>(result, 0x8000000, true);
+         test_power_of_2<uint64_t>(result, 0x100000000000, true);
+
+         return result;
+         }
+   };
+
+BOTAN_REGISTER_TEST("bit_ops", BitOps_Tests);
+
 #if defined(BOTAN_HAS_POLY_DBL)
 
 class Poly_Double_Tests final : public Text_Based_Test
diff --git a/src/tests/tests.cpp b/src/tests/tests.cpp
index 71c3e3726..2300dfaea 100644
--- a/src/tests/tests.cpp
+++ b/src/tests/tests.cpp
@@ -12,7 +12,6 @@
 #include <botan/hex.h>
 #include <botan/parsing.h>
 #include <botan/internal/filesystem.h>
-#include <botan/internal/bit_ops.h>
 #include <botan/internal/stl_util.h>
 
 #if defined(BOTAN_HAS_BIGINT)