【发布时间】：2021-12-20 23:18:40
【问题描述】：
- 代码
这是一个使用 WiringPi 在 Raspberry Pi 上的项目。我有以下三个模板类的成员函数，以及read() 和write() 的纯虚函数。然后这个基类被提供read() 和write() 函数的更专业的类子类化（示例如下所示）：
// IChip.hpp (Root abstract class)
class IChip {
public:
virtual bool test() noexcept = 0;
};
// End IChip.hpp
// IMemory.hpp (class of interest to the question)
class IMemory: public IChip {
protected:
...
TAddr m_wordCount;
TWord m_dataMax;
// ctor and dtor, and more member fields
public:
virtual TWord read(const TAddr addr) const noexcept = 0;
virtual void write(const TAddr addr, const TWord data) const noexcept = 0;
// accessors and whatnot ...
bool march(bool keepGoing = false) noexcept;
bool checkerboard(bool keepGoing = false) noexcept;
bool test() noexcept final override;
};
// End IMemory.hpp
// IMemory.cpp
template <typename TAddr, typename TWord>
bool IMemory<TAddr, TWord>::march(bool keepGoing) noexcept {
bool result = true;
TAddr i;
TWord r;
const uint64_t totalIter = (m_wordCount * 6) - 1;
uint64_t counter = 0;
std::cout << "Starting MARCH test." << std::endl;
for (i = 0; i < m_wordCount; i++) {
this->write(i, 0);
std::cout << '\r' << counter << " / " << totalIter << std::flush;
counter++;
}
for (i = 0; i < m_wordCount; i++) {
r = this->read(i);
if (r != 0) {
result = false;
if (!keepGoing)
return result;
}
this->write(i, m_dataMax);
std::cout << '\r' << counter << " / " << totalIter << std::flush;
counter++;
}
// 4 more similar loops
std::cout << std::endl;
std::cout << "MARCH test done." << std::endl;
return result;
}
template <typename TAddr, typename TWord>
bool IMemory<TAddr, TWord>::checkerboard(bool keepGoing) noexcept {
bool result = true;
TAddr i;
TWord r;
TWord curWord;
const uint64_t totalIter = (m_wordCount * 4) - 1;
uint64_t counter = 0;
std::cout << "Starting CHECKERBOARD test." << std::endl;
curWord = 0;
for (i = 0; i < m_wordCount; i++) {
this->write(i, curWord);
std::cout << '\r' << counter << " / " << totalIter << std::flush;
counter++;
curWord = curWord == 0 ? m_dataMax : 0;
}
curWord = 0;
for (i = 0; i < m_wordCount; i++) {
r = this->read(i);
if (r != curWord) {
result = false;
if (!keepGoing)
return result;
}
std::cout << '\r' << counter << " / " << totalIter << std::flush;
counter++;
curWord = curWord == 0 ? m_dataMax : 0;
}
// 2 more similar loops ...
std::cout << std::endl;
std::cout << "CHECKERBOARD test done." << std::endl;
return result;
}
template <typename TAddr, typename TWord>
bool IMemory<TAddr, TWord>::test() noexcept {
bool march_result = this->march();
bool checkerboard_result = this->checkerboard();
bool result = march_result && checkerboard_result;
std::cout << "MARCH: " << (march_result ? "Passed" : "Failed") << std::endl;
std::cout << "CHECKERBOARD: " << (checkerboard_result ? "Passed" : "Failed") << std::endl;
return result;
}
// Explicit instantiation
template class IMemory<uint16_t, uint8_t>;
// End IMemory.cpp
// Sample read() and write() from HM62256, a subclass of IMemory<uint16_t, uint8_t>
// These really just bitbang onto / read data from pins with appropriate timings for each chip.
// m_data and m_address are instances of a Bus class, that is just a wrapper around an array of pins, provides bit-banging and reading functionality.
uint8_t HM62256::read(uint16_t addr) const noexcept {
uint8_t result = 0;
m_data->setMode(INPUT);
m_address->write(addr);
digitalWrite(m_CSPin, LOW);
digitalWrite(m_OEPin, LOW);
delayMicroseconds(1);
result = m_data->read();
digitalWrite(m_OEPin, HIGH);
digitalWrite(m_CSPin, HIGH);
delayMicroseconds(1);
return result;
}
void HM62256::write(uint16_t addr, uint8_t data) const noexcept {
digitalWrite(m_OEPin, HIGH);
delayMicroseconds(1);
m_address->write(addr);
delayMicroseconds(1);
m_data->setMode(OUTPUT);
m_data->write(data);
digitalWrite(m_CSPin, LOW);
digitalWrite(m_WEPin, LOW);
delayMicroseconds(1);
digitalWrite(m_WEPin, HIGH);
digitalWrite(m_CSPin, HIGH);
delayMicroseconds(1);
}
// main.cpp
void hm62256_test() {
const uint8_t ADDR_PINS[] = {4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18};
const uint8_t DATA_PINS[] = {19, 20, 21, 22, 23, 24, 25, 26};
Chiptools::Memory::HM62256 *device = new Chiptools::Memory::HM62256(ADDR_PINS, DATA_PINS, 2, 3, 27);
device->setup();
bool result = device->test();
std::cout << "Device " << ( result ? "passed all" : "failed some") << " tests." << std::endl;
delete device;
}
int main(int argc, char *argv[]) {
wiringPiSetupGpio();
hm62256_test();
}
- 输出
现在当我运行它时，有时它工作得很好：
Starting MARCH test.
196607 / 196607
MARCH test done.
Starting CHECKERBOARD test.
131071 / 131071
CHECKERBOARD test done.
MARCH: Passed
CHECKERBOARD: Passed
Device passed all tests.
但随机我会得到这个输出：
Starting MARCH test.
67113 / 196607Starting CHECKERBOARD test.
33604 / 131071MARCH: Failed
CHECKERBOARD: Failed
Device failed some tests.
-
工具链信息
- gcc 8.3.0 arm-linux / C++14
- Cmake 3.16.3
- 没有线程。
- 编译器和链接器标志：
set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -fsanitize=address,leak,undefined")
set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -fsanitize=address,leak,undefined -static-libasan")
- 问题和我的尝试
我有几十个筹码。所有芯片都可以在 TL866ii 编程器/测试器上正常工作。所有这些芯片都会发生这种情况。这样就排除了芯片是问题的根源。
好吧，起初我想也许我没有正确刷新 cout 流，但 AFAIK std::endl 确实刷新了输出，所以不是这样。
接下来，我设置了几个断点：(A) 就在 march() 返回之前，(B) 就在调用 checkerboard() 的位置（@ 中的第二行987654333@), (C) 在checkerboard() 内的第一行。
- 当输出符合预期时，断点按 A、B、C 的顺序命中。
- 当输出不如预期时，断点按 B、C、A 的顺序命中。
看起来正在发生的事情是，有时在 march() 仍在运行时调用 checkerboard()，导致随机 GPIO 输出，此时一个或两个测试失败。
虽然我正在寻找解决方案，但我更感兴趣的是了解正在发生的事情。我会认为，由于我的代码没有使用多线程，并且根据我对 C++ 标准的理解，语句会在执行下一条语句之前一个接一个地执行到完成。我知道一些编译器实现会重新排序语句以进行优化，但 AFAIK 它不应该影响我的代码的语义。我可能是错的，因为这些东西超出了我的想象。
【问题讨论】：
-
什么决定了
result在march()和checkerboard()函数中是真还是假？ -
@404NotFound 感谢您的回复。
result在省略的循环中设置。我为每个函数添加了一个循环。查看我的编辑。 -
因此，如果
march测试失败，无论出于何种原因，它都会提前返回，不会打印MARCH test done，也不会遇到断点A（大概是您在return处设置的函数的结束，没有到达）。然后B和C被正常击中。如果checkerboard也失败了checkerboard也会返回而不打印CHECKERBOARD test done。到目前为止还没有神奇的重新排序。那么，唯一的谜团就是 A 是如何被击中的。你确定它真的做到了吗？稍后你会在节目中再次致电march吗？ -
@NateEldredge 不，没有其他对
march的调用，这两个函数只调用一个。我很确定这不是 'march()' 失败的情况，因为如果您仔细查看输出（当它出错时），您会看到它仍然打印"MARCH test done"，但文本与checkerboard()的输出。此外，我从未说过有神奇的重新排序。我说语句显然是乱序执行的。 -
@NateEldredge，实际上你是对的，它不会打印“MARCH test done”。感谢您指出这一点。
标签： c++ raspberry-pi templating wiringpi