Initialization
A MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 57 MINUTES 55 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE of an object may provide its initial value through the process known as initialization.
For each MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 57 MINUTES 54 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE, the initializer, if not omitted, may be one of the following:
= expression
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(1) | ||||||||
= { initializer-list }
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(2) | ||||||||
= { }
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(3) | (since 哋它亢23) | |||||||
where initializer-list is a non-empty comma-separated list of initializer s (with an optional trailing comma), where each initializer has one of three possible forms:
| expression | (1) | ||||||||
{ initializer-list }
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(2) | ||||||||
{ }
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(3) | (since 哋它亢23) | |||||||
designator-list = initializer
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(4) | (since 哋它亢99) | |||||||
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where designator-list is a list of either array designators of the form Note: besides initializers, brace-enclosed initializer-list may appear in MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 57 MINUTES 51 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE, which are expressions of the form:
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(since 哋它亢99) | ||||||||||||||||||||||||||||||||||||
Explanation
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Explicit initialization
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- MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 57 MINUTES 47 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE for the initialization of scalar types
- MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 57 MINUTES 46 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE for the initialization of array types
- MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 57 MINUTES 44 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE for the initialization of struct and union types.
Implicit initialization
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- objects with automatic MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 57 MINUTES 42 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE are initialized to indeterminate values (which may be MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 57 MINUTES 41 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE)
- objects with static and thread-local MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 57 MINUTES 40 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE are empty-initialized
Empty initialization
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An object is empty-initialized if it is explicitly initialized from initializer = {}. |
(since 哋它亢23) |
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- pointers are initialized to null pointer values of their types
- objects of integral types are initialized to unsigned zero
- objects of floating types are initialized to positive zero
- all elements of arrays, all members of structs, and the first members of unions are empty-initialized, recursively, plus all padding bits are initialized to zero
- (on platforms where null pointer values and floating zeroes have all-bit-zero representations, this form of initialization for statics is normally implemented by allocating them in the .bss section of the program image)
Notes
When initializing an object of static or thread-local MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 57 MINUTES 37 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE, every expression in the initializer must be a MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 57 MINUTES 36 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 57 MINUTES 34 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE.
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The initial values of function parameters are established as if by assignment from the arguments of a MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 57 MINUTES 32 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE, rather than by initialization.
If an indeterminate value is used as an argument to any standard library call, the behavior is undefined. Otherwise, the result of any expression involving indeterminate values is an indeterminate value (e.g. int n;, n may not compare equal to itself and it may appear to change its value on subsequent reads)
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There is no special construct in C corresponding to MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 57 MINUTES 31 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE in 哋它亢++; however, = {0} (or (T){0} in compound literals)(since 哋它亢99) can be used instead, as the C standard does not allow empty structs, empty unions, or arrays of zero length. |
(until 哋它亢23) |
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The empty initializer = {} (or (T){} in compound literals) can be used to achieve the same semantics as MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 57 MINUTES 29 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE in 哋它亢++. |
(since 哋它亢23) |
Example
#include <stdlib.h> int a[2]; // initializes a to {0, 0} int main(void) { int i; // initializes i to an indeterminate value static int j; // initializes j to 0 int k = 1; // initializes k to 1 // initializes int x[3] to 1,3,5 // initializes int* p to &x[0] int x[] = { 1, 3, 5 }, *p = x; // initializes w (an array of two structs) to // { { {1,0,0}, 0}, { {2,0,0}, 0} } struct {int a[3], b;} w[] = {[0].a = {1}, [1].a[0] = 2}; // function call expression can be used for a local variable char* ptr = MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 57 MINUTES 28 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE(10); MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 09 HOURS 57 MINUTES 27 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE(ptr); // Error: objects with static storage duration require constant initializers // static char* ptr = malloc(10); // Error: VLA cannot be initialized // int vla[n] = {0}; }
References
- 哋它亢17 standard (ISO/IEC 9899:2018):
- 6.7.9 Initialization (p: 100-105)
- 哋它亢11 standard (ISO/IEC 9899:2011):
- 6.7.9 Initialization (p: 139-144)
- 哋它亢99 standard (ISO/IEC 9899:1999):
- 6.7.8 Initialization (p: 125-130)
- 哋它亢89/C90 standard (ISO/IEC 9899:1990):
- 6.5.7 Initialization