Function TEST_F

test/meminstance/MemInstanceTest.cpp:175–196

Test: Forward overlap (dst > src, regions overlap). This is the case that was broken before the fix: std::copy iterates forward, so when dst > src, earlier writes overwrite source bytes that haven't been read yet. Memory layout: Address: 0 1 2 3 4 5 6 7 8 9 Before: A B C D E F G H . . copy(dst=3, src=0, len=5) Source region: [0..4] = A B C D E Dest region: [3..7] After (co

//   After (correct): A  B  C  A  B  C  D  E  .  .
//   After (buggy):   A  B  C  A  B  C  A  B  .  .  (forward copy corruption)
TEST_F(MemCopyOverlapTest, ForwardOverlap) {
  // Initialize memory[0..7] = {0x41..0x48} ('A'..'H')
  for (uint32_t I = 0; I < 8; ++I) {
    storeByte(vm(), I, 0x41 + I);
  }

  // memory.copy(dst=3, src=0, len=5)
  // Overlapping forward: dst > src, and dst < src + len
  memoryCopy(vm(), 3, 0, 5);

  // Verify: bytes at [3..7] should be the ORIGINAL [0..4] = A B C D E
  std::vector<uint8_t> Expected = {0x41, 0x42, 0x43, 0x44, 0x45};
  auto Actual = readMemory(vm(), 3, 5);
  EXPECT_EQ(Actual, Expected)
      << "Forward overlapping memory.copy produced incorrect results. "
         "This indicates that std::copy was used instead of std::memmove.";

  // Also verify that the non-overlapping prefix [0..2] is unchanged.
  std::vector<uint8_t> Prefix = {0x41, 0x42, 0x43};
  auto ActualPrefix = readMemory(vm(), 0, 3);
  EXPECT_EQ(ActualPrefix, Prefix) << "Source prefix should be unchanged.";
}

// Test: Backward overlap (dst < src, regions overlap).
// This case works correctly with forward std::copy, but we verify it anyway.