What does the 'ULL' suffix signify in C/C numeric literals?

Understanding Numeric Literals with ULL Suffix

In C/C programming, numeric literals can be specified with various suffixes to indicate their integer data type and size. One such suffix is "ULL," which you encountered in the code snippet:

line += addr & 0x3fULL;

Indeed, "ULL" stands for "Unsigned Long Long." It suggests that the numeric literal "0x3f" should be interpreted as an unsigned long long int.

According to the C standard library, adding the "ULL" suffix to an integer constant denotes an unsigned long long int type. This suffix is introduced to support integers with a width of at least 64 bits.

Using ULL for Unsigned Long Long Integers

In the provided code example:

• addr is a variable of type addr_t, which is likely an integer type with a width of at least 32 bits.
• 0x3f is a hexadecimal literal representing 63.
• The bitwise AND operation (&) with 0x3f extracts the lower 6 bits from addr.
• By appending "ULL" to the literal, you explicitly cast the result to an unsigned long long int, ensuring that it has a width of 64 bits.

Conclusion

The "ULL" suffix for numeric literals allows you to represent large integers with an unsigned long long data type. It is essential for handling numbers that exceed the range of standard integer types, ensuring accurate representation and avoiding overflow errors.

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