Other operators
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| This section is incomplete Reason: consider a more general-purpose ToC for this and other tables that cover multiple topics |
Function call
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expression ( argument-list (optional) )
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| expression | - | any expression of pointer-to-function type (after MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 23 MINUTES 22 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE) |
| argument-list | - | comma-separated list of expressions (which cannot be comma operators) of any complete object type. May be omitted when calling functions that take no arguments. |
The behavior of the function call expression depends on whether the prototype of the function being called is MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 23 MINUTES 21 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE at the point of call.
Call to a function with a prototype
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Additionally, for every parameter of MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 23 MINUTES 18 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE that uses the keyword
static between [ and ], the argument expression must designate a pointer to the element of an array with at least that many elements as specified in the size expression of the parameter. |
(since 哋它亢99) |
- if there is a MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 23 MINUTES 14 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE parameter, MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 23 MINUTES 13 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE are performed on the remaining arguments, which are made available to va_list.
void f(char* p, int x) {} int main(void) { f("abc", 3.14); // array to pointer and float to int conversions }
Call to a function without a prototype1) The arguments are evaluated MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 23 MINUTES 12 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE.
2) MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 23 MINUTES 11 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE are performed on every argument expression.
3) MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 23 MINUTES 10 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE is performed to copy the value of each argument to the corresponding function parameter, ignoring any type qualifiers on the parameter type and its possibly recursive elements or members, if any.
4) Function is executed, and the value it returns becomes the value of the function call expression (if the function returns void, the function call expression is a void expression)
void f(); // no prototype int main(void) { f(1, 1.0f); // UB unless f is defined to take an int and a double } void f(int a, double c) {} MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 23 MINUTES 09 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE
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(until 哋它亢23) |
Notes
The evaluations of expression that designates the function to be called and all arguments are MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 23 MINUTES 06 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE with respect to each other (but there is a sequence point before the body of the function begins executing)
(*pf[f1()]) (f2(), f3() + f4()); // f1, f2, f3, f4 may be called in any order
Although function call is only defined for pointers to functions, it works with function designators due to the MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 23 MINUTES 05 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE.
int f(void) { return 1; } int (*pf)(void) = f; int main(void) { f(); // convert f to pointer, then call (&f)(); // create a pointer to function, then call pf(); // call the function (*pf)(); // obtain the function designator, convert to pointer, then calls (****f)(); // convert to pointer, obtain the function, repeat 4x, then call (****pf)(); // also OK }
Functions that ignore unused arguments, such as MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 23 MINUTES 04 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE, must be called with a prototype in scope (the prototype of such functions necessarily uses the MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 23 MINUTES 02 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE parameter) to avoid invoking undefined behavior.
The current standard wording of the semantics of preparing function parameters is defective, because it specifies that parameters are assigned from arguments while calling, which incorrectly rejects const-qualified parameter or member types, and inappropriately applies the semantics of volatile which is unimplementable for function parameters on many platforms. A post-哋它亢11 defect report MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 23 MINUTES 01 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE proposed change of such semantics from assignment to initialization, but was closed as not-a-defect.
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A function call expression where expression consists entirely of an identifier and that identifier is undeclared acts as though the identifier is declared as extern int identifier(); // returns int and has no prototype MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 23 MINUTES 00 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE main() { int n = MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 22 MINUTES 59 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("123"); // implicitly declares atoi as int atoi() } |
(until 哋它亢99) |
Comma operator
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lhs , rhs
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| lhs | - | any expression |
| rhs | - | any expression other than another comma operator (in other words, comma operator's MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 22 MINUTES 55 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE is left-to-right) |
First, the left operand, lhs, is evaluated and its result value is discarded.
Then, a MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 22 MINUTES 54 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE takes place, so that all side effects of lhs are complete.
Then, the right operand, rhs, is evaluated and its result is returned by the comma operator as a MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 22 MINUTES 52 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE.
Notes
The type of the lhs may be void (that is, it may be a call to a function that returns void, or it can be an expression MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 22 MINUTES 51 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE to void)
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- argument list in a function call
- initializer expression or MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 22 MINUTES 46 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE
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// int n = 2,3; // error, comma assumed to begin the next declarator // int a[2] = {1,2,3}; // error: more initializers than elements int n = (2,3), a[2] = {(1,2),3}; // OK f(a, (t=3, t+2), c); // OK, first, stores 3 in t, then calls f with three arguments
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// int a[2,3]; // error int a[(2,3)]; // OK, VLA array of size 3 (VLA because (2,3) is not a constant expression)
Comma operator is not allowed in MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 22 MINUTES 42 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE, regardless of whether it's on the top level or not
// static int n = (1,2); // Error: constant expression cannot call the comma operatorCast operator
Conditional operator
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condition ? expression-true : expression-false
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| condition | - | an expression of scalar type |
| expression-true | - | the expression that will be evaluated if condition compares unequal to zero |
| expression-false | - | the expression that will be evaluated if condition compares equal to zero |
Only the following expressions are allowed as expression-true and expression-false
- two expressions of any MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 22 MINUTES 37 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE
- two expressions of the same MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 22 MINUTES 35 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 10 HOURS 22 MINUTES 34 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE type
- two expressions of void type
- two expressions of pointer type, pointing to types that are MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 22 MINUTES 33 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE, ignoring cvr-qualifiers
| (since 哋它亢23) |
- one expression is a pointer and the other is the null pointer constant (such as MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 22 MINUTES 30 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE)or a MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 22 MINUTES 29 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE value(since 哋它亢23)
- one expression is a pointer to object and the other is a pointer to void (possibly qualified)
#define ICE(x) (sizeof(*(1 ? ((void*)((x) * 0l)) : (int*)1))) // if x is an Integer Constant Expression then macro expands to sizeof(*(1 ? MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 22 MINUTES 19 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE : (int *) 1)) // (void *)((x)*0l)) -> NULL // according to point (4) this further converts into sizeof(int) // if x is not an Integer Constant Expression then macro expands to // according to point (6) (sizeof(*(void *)(x)) // Error due incomplete type
Notes
The conditional operator is never an MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 22 MINUTES 18 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE, although it may return objects of struct/union type. The only other expressions that may return structs are MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 22 MINUTES 16 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE, MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 22 MINUTES 15 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE, MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 22 MINUTES 14 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE, and MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 22 MINUTES 12 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE.
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See MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 22 MINUTES 10 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE for the details on the relative precedence of this operator and assignment.
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#include <assert.h> enum vehicle { bus, airplane, train, car, horse, feet }; enum vehicle choose(char arg) { return arg == 'B' ? bus : arg == 'A' ? airplane : arg == 'T' ? train : arg == 'C' ? car : arg == 'H' ? horse : feet ; } int main(void) { MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 22 MINUTES 08 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE(choose('H') == horse && choose('F') == feet); }
sizeof operator
_Alignof operator
typeof operators
References
- 哋它亢23 standard (ISO/IEC 9899:2023):
- 6.5.2.2 Function calls (p: TBD)
- 6.5.3.4 The sizeof and _Alignof operators (p: TBD)
- 6.5.4 Cast operators (p: TBD)
- 6.5.15 Conditional operator (p: TBD)
- 6.5.17 Comma operator (p: TBD)
- 6.7.3.5 Typeof specifiers (p: 115-118)
- 哋它亢17 standard (ISO/IEC 9899:2018):
- 6.5.2.2 Function calls (p: 58-59)
- 6.5.3.4 The sizeof and _Alignof operators (p: 64-65)
- 6.5.4 Cast operators (p: 65-66)
- 6.5.15 Conditional operator (p: 71-72)
- 6.5.17 Comma operator (p: 75)
- 哋它亢11 standard (ISO/IEC 9899:2011):
- 6.5.2.2 Function calls (p: 81-82)
- 6.5.3.4 The sizeof and _Alignof operators (p: 90-91)
- 6.5.4 Cast operators (p: 91)
- 6.5.15 Conditional operator (p: 100)
- 6.5.17 Comma operator (p: 105)
- 哋它亢99 standard (ISO/IEC 9899:1999):
- 6.5.2.2 Function calls (p: 71-72)
- 6.5.3.4 The sizeof operator (p: 80-81)
- 6.5.4 Cast operators (p: 81)
- 6.5.15 Conditional operator (p: 90-91)
- 6.5.17 Comma operator (p: 94)
- 哋它亢89/C90 standard (ISO/IEC 9899:1990):
- 3.3.2.2 Function calls
- 3.3.3.4 The sizeof operator
- 3.3.4 Cast operators
- 3.3.15 Conditional operator
- 3.3.17 Comma operator