c++ - 什么是 clang-check 的垃圾值

Question

我收到以下警告:

test.cpp:14:25: warning: The right operand of '/' is a garbage value
    return (std::abs(a) / size) > 10;
                        ^ ~~~~

对于这段代码:

#include <algorithm>
#include <complex>
#include <vector>
#include <iostream>

using namespace std;
double
pitchDetect(const std::vector<std::complex<double>> &dft,
                              unsigned int samplingRate) noexcept {
  if (dft.empty())
    return 0.0;
  auto it = find_if(begin(dft), end(dft),
                    [size = dft.size()](const std::complex<double> &a) {
    return (std::abs(a) / size) > 10;
  });
  return 0.0;
}

我不明白这是什么问题!

Answer 1

这看起来像 bug 22833 ，固定在主干中:

Giving a lambda capture parameter an explicit value (new feature in C++14) causes the analyzer to believe that value is undefined.

作为解决方法，您可以尝试将 init-capture 提升到 lambda 之外:

  auto const size = dft.size();
  auto it = find_if(begin(dft), end(dft),
                    [size](const std::complex<double> &a) {
    return (std::abs(a) / size) > 10;
  });