MISRA Discussion Forums
Rule 8-5-2 what is "non-zero initialization"? - Printable Version

+- MISRA Discussion Forums (https://forum.misra.org.uk)
+-- Forum: MISRA C++ (https://forum.misra.org.uk/forumdisplay.php?fid=18)
+--- Forum: MISRA C++:2008 rules (https://forum.misra.org.uk/forumdisplay.php?fid=19)
+---- Forum: 6.8 Declarators (C++) (https://forum.misra.org.uk/forumdisplay.php?fid=137)
+---- Thread: Rule 8-5-2 what is "non-zero initialization"? (/showthread.php?tid=1308)

Rule 8-5-2 what is "non-zero initialization"? - grunwald - 24-01-2017

C++ has the concepts:
  • default initialization ("T var;")
    Calls the default constructor (if it exists); otherwise the memory is left uninitialized.

  • value initialization ("T var = {};")
    Calls the default constructor if it exists and is user-defined.
    Otherwise, performs zero-initialization and then calls the compiler-generated default constructor (if it exists).

  • zero initialization
    Roughly equivalent to a memset(..., 0, ...)

The term "non-zero initialization" is not defined anywhere.

Code:
struct POD { int member1; int member2; };
class UserDefinedCtor { public: UserDefinedCtor(); };
struct CompilerDefinedCtor { int member1; UserDefinedCtor member2; };

POD pod[3] = {}; // value initialization that uses zero initialization
UserDefinedCtor udc[3] = {}; // value initialization but does not involve zero initialization
CompilerDefinedCtor cdc[3] = {}; // value initialization that involves both zero initialization and constructor calls

The declaration `pod` is clearly compliant with Rule 8-5-2.

What about `udc`? If it is classified as "non-zero initialization", Rule 8-5-2 would require an explicit initializator for each element:
Code:
UserDefinedCtor udc[3] = { UserDefinedCtor(), UserDefinedCtor(), UserDefinedCtor() };

But maybe "zero initialization" in this rule does not refer to the C++ concept, but instead to the syntactic forms "{}", "{0}" and "{NULL}" ?

Re: Rule 8-5-2 what is "non-zero initialization"? - misra cpp - 12-07-2017

We agree with your interpretation and this will be addressed in the next version