Consider the following code
Clang completely removes the for-loop with optimisation -O3. I am a bit surprised. Although testVector will contain only garbage, I expected the loop not to be removed (actually also no warning was issued, only the analyser detected that testVector contains garbage).
If I add a line assigning a value to a random element of testVector, the loop is not removed.
PS: I wanted to use the loop for testing the execution speed of malloc and free.
Code Block language #include <chrono> #include <iostream> #include <random> #include <vector> class TestClass { public: int A = 0; int B = 4; protected: private: }; int main(int argc, const char * argv[]) { std::random_device randomDevice; std::mt19937 mersenneTwister(randomDevice()); std::uniform_int_distribution<size_t> distribution(1,255); for (size_t i=0; i<10000000; ++i) { size_t const vectorSize = distribution(mersenneTwister)+1; TestClass* testVector(reinterpret_cast<TestClass*>(malloc(vectorSize*sizeof(TestClass)))); if (testVector[0].A == 0x0ffeefed) { std::cout << "Sorry value hit." << std::endl; break; } /* if */ free(testVector); } /* for */ return 0; }
Clang completely removes the for-loop with optimisation -O3. I am a bit surprised. Although testVector will contain only garbage, I expected the loop not to be removed (actually also no warning was issued, only the analyser detected that testVector contains garbage).
If I add a line assigning a value to a random element of testVector, the loop is not removed.
PS: I wanted to use the loop for testing the execution speed of malloc and free.
