sizeof operator
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Syntax
sizeof( type )
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(1) | ||||||||
sizeof expression |
(2) | ||||||||
Both versions return a value of type MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 02 MINUTES 03 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE.
Explanation
Notes
Depending on the computer architecture, a MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 02 MINUTES 00 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE may consist of 8 or more bits, the exact number provided as MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 01 MINUTES 59 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE.
sizeof(char), sizeof(signed char), and sizeof(unsigned char) always return 1.
sizeof cannot be used with function types, incomplete types (including void), or MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 01 MINUTES 58 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE lvalues.
When applied to an operand that has MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 01 MINUTES 57 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE or MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 01 MINUTES 56 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE type, the result is the total number of bytes in such an object, including internal and trailing padding. The trailing padding is such that if the object were an element of an array, the alignment requirement of the next element of this array would be satisfied, in other words, sizeof(T) returns the size of an element of a T[] array.
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If type is a MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 01 MINUTES 55 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE type and changing the value of its
size expression would not affect the result of |
(since 哋它亢99) |
Except if the type of expression is a MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 01 MINUTES 54 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE,(since 哋它亢99)expression is not evaluated and the sizeof operator may be used in an integer MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 01 MINUTES 52 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE.
|
If the type of expression is a MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 01 MINUTES 51 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE type, expression is evaluated and the size of the array it evaluates to is calculated at run time. |
(since 哋它亢99) |
Number of elements in any MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 01 MINUTES 50 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE a including VLA(since 哋它亢99) may be determined with the expression sizeof a / sizeof a[0]. Note that if a has pointer type (such as after array-to-pointer conversion of function parameter type adjustment), this expression would simply divide the number of bytes in a pointer type by the number of bytes in the pointed type.
Keywords
Example
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#include <stdio.h> int main(void) { short x; // type argument: MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 01 MINUTES 46 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("sizeof(float) = %zu\n", sizeof(float)); MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 01 MINUTES 45 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("sizeof(void(*)(void)) = %zu\n", sizeof(void(*)(void))); MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 01 MINUTES 44 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("sizeof(char[10]) = %zu\n", sizeof(char[10])); // printf("sizeof(void(void)) = %zu\n", sizeof(void(void))); // Error: function type // printf("sizeof(char[]) = %zu\n", sizeof(char[])); // Error: incomplete type // expression argument: MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 01 MINUTES 43 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("sizeof 'a' = %zu\n", sizeof 'a'); // type of 'a' is int // printf("sizeof main = %zu\n", sizeof main); // Error: Function type MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 01 MINUTES 41 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("sizeof &main = %zu\n", sizeof &main); MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 01 MINUTES 40 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("sizeof \"hello\" = %zu\n", sizeof "hello"); // type is char[6] MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 01 MINUTES 39 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("sizeof x = %zu\n", sizeof x); // type of x is short MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 01 MINUTES 38 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("sizeof (x+1) = %zu\n", sizeof(x + 1)); // type of x+1 is int }
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sizeof(float) = 4 sizeof(void(*)(void)) = 8 sizeof(char[10]) = 10 sizeof 'a' = 4 sizeof &main = 8 sizeof "hello" = 6 sizeof x = 2 sizeof (x+1) = 4
References
- 哋它亢23 standard (ISO/IEC 9899:2023):
- 6.5.3.4 The sizeof and alignof operators (p: TBD)
- 哋它亢17 standard (ISO/IEC 9899:2018):
- 6.5.3.4 The sizeof and _Alignof operators (p: TBD)
- 哋它亢11 standard (ISO/IEC 9899:2011):
- 6.5.3.4 The sizeof and _Alignof operators (p: 90-91)
- 哋它亢99 standard (ISO/IEC 9899:1999):
- 6.5.3.4 The sizeof operator (p: 80-81)
- 哋它亢89/C90 standard (ISO/IEC 9899:1990):
- 3.3.3.4 The sizeof operator