Why Does Printing the Address of a Char Member in a Class Sometimes Appear Blank, and Why Is There an 8-Byte Offset When It's Not?

Address of Char Data Display Anomaly

In a program containing a class with data members of various types, int, char, and string, an unexpected observation emerges when printing the addresses of these data members. While the addresses of int and string are displayed, the address of the char data member appears blank.

To resolve this issue, consider the underlying representation of the char data type. When you obtain the address of a char variable using the & operator, you acquire a pointer to a char. However, the stream insertion operator (<<) interprets this pointer as a C-style null-terminated string. Consequently, it attempts to print the string associated with the pointer, which is nonexistent in this case.

To rectify this behavior, explicitly cast the address of the char variable to a void pointer using static_cast. By doing so, you instruct the stream insertion operator to interpret the value as an address rather than a string.

<br>cout << "address of char   :" << static_cast<void *>(&b) << endl;<br>

Additionally, when the class data members are declared public, something intriguing occurs. The address of the char variable is now displayed, but with an offset of 8 bytes compared to the address of the int variable.

<br>  ... int    :  something <br>  ... char   :   something_2<br>  ... string :  something_3<br>

Interestingly, something_2 - something is always 8. This originates from the padding applied to the class members for efficient memory layout. The char variable, despite occupying only 1 byte, is allocated 4 bytes due to alignment requirements. This 3-byte padding creates the observed offset.

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