Похожие типы (int16_t и short) ведут себя по-разному во время создания экземпляра ссылки. ⇐ C++

[Anonymous]

I'm running into the following error depending on which type I choose for a variable.

/home/zak/Development/Arduino/generated_examples/ArduinoIoTCloud_Basic/thingProperties.h: In function 'void initProperties()': /home/zak/Development/Arduino/libraries/ArduinoIoTCloud/src/ArduinoIoTCloud.h:116:64: error: cannot bind non-const lvalue reference of type 'int16_t& {aka int&}' to an rvalue of type 'int16_t {aka int}' #define addProperty( v, ...) addPropertyReal(v, #v, __VA_ARGS__) ^ /home/zak/Development/Arduino/generated_examples/ArduinoIoTCloud_Basic/thingProperties.h:32:16: note: in expansion of macro 'addProperty' ArduinoCloud.addProperty(potentiometer, 2, Permission::Read).publishOnChange(10); ^ In file included from /home/zak/Development/Arduino/generated_examples/ArduinoIoTCloud_Basic/ArduinoIoTCloud_Basic.ino:17:0: /home/zak/Development/Arduino/libraries/ArduinoIoTCloud/src/ArduinoIoTCloud.h:158:15: note: initializing argument 1 of 'Property& ArduinoIoTCloudClass::addPropertyReal(int16_t&, String, int, Permission)' Property& addPropertyReal(int16_t& property, String name, int tag, Permission const permission); ^~~~~~~~~~~~~~~ Here is the body of addPropertyReal():

Property& ArduinoIoTCloudClass::addPropertyReal(int16_t& property, String name, int tag, Permission const permission) { Property* p = new CloudWrapperInt16(property); return addPropertyReal(*p, name, tag, permission); } The problem happens when newing CloudWrapperInt16:

class CloudWrapperInt16 : public CloudWrapperBase { private: int16_t &_primitive_value, _cloud_value, _local_value; public: CloudWrapperInt16(int16_t& v) : _primitive_value(v), _cloud_value(v), _local_value(v) {} ... ^^ As you can see, _primitive_value is a reference.
16-bit architecture, avr-gcc compiler
Oddly, this works when I pass an actual int or int16_t. However, I run into this error whenever I pass in a value that is equivalent but must be cast into a int16_t, like short.

SUCCESS (int16_t): (compiles without warnings)

int16_t potentiometer; ... void initProperties() { ... ArduinoCloud.addProperty(potentiometer, Permission::Read).publishOnChange(10); SUCCESS (int): (compiles without warnings)

int potentiometer; ... void initProperties() { ... ArduinoCloud.addProperty(potentiometer, Permission::Read).publishOnChange(10); FAIL (short): (error shown above)

short potentiometer; ... void initProperties() { ... ArduinoCloud.addProperty(potentiometer, Permission::Read).publishOnChange(10); EDIT: Originally, I forgot to mention that this particular example is compiling for a 16-bit platform. So int, short and int16_t should all be the same size.
32-bit architecture, arm-none-eabi-gcc compiler
In a really bizarre twist, this works when I pass a short or int16_t. However, I run into a similar error whenever I pass in an int value.

SUCCESS (int16_t): (compiles without warnings)

int16_t potentiometer; ... void initProperties() { ... ArduinoCloud.addProperty(potentiometer, Permission::Read).publishOnChange(10); SUCCESS (short): (compiles without warnings)

short potentiometer; ... void initProperties() { ... ArduinoCloud.addProperty(potentiometer, Permission::Read).publishOnChange(10); FAIL (int): (similar error as shown above)

int potentiometer; ... void initProperties() { ... ArduinoCloud.addProperty(potentiometer, Permission::Read).publishOnChange(10); Can someone explain what exactly is happening here with the type conversion?

I'm looking for a POSIX compliant way for to the compiler to treat them equivalently, or a way to enhance the code to allow this to work. Any solution will need to compile for multiple architectures (16-bit, 32-bit, etc.), as well as work on multiple toolchains (avr-gcc, arm-none-eabi-g++, etc.).

NOTE: I don't have control over the code base; it is a large open-source project. I really need a surgical solution, because the more broad the refactor work, the harder it will be to get the PR accepted.


Источник: https://stackoverflow.com/questions/781 ... ng-referen