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Added missing virtual destructors #218

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Added missing virtual destructors #218

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2 changes: 2 additions & 0 deletions api/Print.h
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Original file line number Diff line number Diff line change
Expand Up @@ -42,6 +42,8 @@ class Print
void setWriteError(int err = 1) { write_error = err; }
public:
Print() : write_error(0) {}
virtual ~Print() {}


int getWriteError() { return write_error; }
void clearWriteError() { setWriteError(0); }
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1 change: 1 addition & 0 deletions api/Printable.h
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Expand Up @@ -33,6 +33,7 @@ class Print;
class Printable
{
public:
virtual ~Printable() {}
virtual size_t printTo(Print& p) const = 0;
};

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2 changes: 1 addition & 1 deletion api/String.h
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Expand Up @@ -81,7 +81,7 @@ class String
explicit String(unsigned long, unsigned char base=10);
explicit String(float, unsigned char decimalPlaces=2);
explicit String(double, unsigned char decimalPlaces=2);
~String(void);
virtual ~String(void);
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Why do you think that String warrants a virtual destructor? Is there any virtual function in the class? On a quick glance I could not find one.

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This question answer is as simple as understanding if we want to allow the user to extend the arduino::String class

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This question answer is as simple as understanding if we want to allow the user to extend the arduino::String class

Undefined behaviour is related to having any virtual function, not to inheritance.
So currently, we do need to add a virtual destructor to Print because it has a virtual functions.

Thus, a virtual destructor is not currently a necessity for String. I can inherit from String, ex. MyString and use MyString all along my code, without any undefined behaviour.

However, you might want to add a virtual destructor to String because you expect users to add virtual functions to their MyString. But that's more about securing the code about expected usages than fixing the current code.

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I can have memory leaks if in MyString class I allocate something that needs to be deleted, I create a proper destructor, I reference it with a pointer to String then I delete it, the derived class destructor is not called.

The answer, in my opinion, is not strictly limited to "String doesn't have virtual methods", because I could want some features of String class and extend them with my custom features. I think you can implement a solution in other better ways, like by embedding String instead. Thus my question: do we want to allow the user to extend String class?


// memory management
// return true on success, false on failure (in which case, the string
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