switch-case
Like goto, switch-case is a label. Without {}, any variable declared within a switch-case statement has the scope of the entire statement. This will only work with variables that can be default-initialized, because they can be declared only with an intermediate value. This creates a problem: what if a variable that cannot be default initialized is created?
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// A can be default-initialized
class A {
public:
A ()=default;
};
class C{
public:
C(){} // This is NOT default initialization
};
int main()
{
int i = 1;
switch (i)
{
case 0:
A j; // Compiler implicitly calls default constructor, fine
int b; // POD can be declared only, fine.
int d = 1; // ERROR: jumping over initialization
C c; // ERROR: jumping over initialization of 'C'
break;
case 1:
b = 2; // This is assignment, not initialization, fine
break;
}
}
This is a typical “Jump Over Initialization” error, where initialization may not happen before a variable gets used. (int d = 1; is another example, because its initialization may not be executed.)
In this case, the best practice is to limit the scope of the variable:
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case 0:{
int d = 1; // fine
C c; // fine
break;
}
