c++ - Should pointers to "raw" resources be zeroed in destructors? -

c++ - Should pointers to "raw" resources be zeroed in destructors? -

when wrap "raw" resources in c++ class, in destructor code release allocated resource(s), without paying attending additional steps zeroing out pointers, etc. e.g.:

class file { public: ... ~file() { if (m_file != null) fclose(m_file); } private: file * m_file; };

i wonder if code style contains potential bug: i.e. is possible destructor called more once? in case, right thing in destructor clear pointers avoid double/multiple destructions:

~file() { if (m_file != null) { fclose(m_file); m_file = null; // avoid double destruction } }

a similar illustration made heap-allocated memory: if m_ptr pointer memory allocated new[], next destructor code ok?

// in destructor: delete [] m_ptr;

or should pointer cleared, too, avoid double destruction?

// in destructor: delete [] m_ptr; m_ptr = null; // avoid double destruction

no. useful if have close() function or like:

void close() { if (m_file != null) { fclose(m_file); m_file = null; } } ~file() { close(); }

this way, close() function idempotent (you can phone call many times want), , avoid 1 test in destructor.

but since destructors in c++ can called once, assigning null pointers there pointless.

unless, of course, debuggin-purposes, particularly if suspect double-delete.

c++ destructor raii