| Labels | ||||
| Expression statements | ||||
| Compound statements | ||||
| Selection statements | ||||
| Iteration statements | ||||
| Jump statements | ||||
goto |
Transfers control unconditionally to the desired location.
Used when it is otherwise impossible to transfer control to the desired location using conventional constructs.
Contents |
attr-spec-seq(optional)gotolabel; | |||||||||
| label | - | targetlabel for thegoto statement |
| attr-spec-seq | - | (C23)optional list ofattributes, applied to thegoto statement |
Thegoto statement causes an unconditional jump (transfer of control) to the statement prefixed by the namedlabel (which must appear in the same function as the goto statement), except when this jump would enter the scope of avariable-length array or anothervariably-modified type.(since C99)
Alabel is an identifier followed by a colon (:) and a statement(until C23). Labels are the only identifiers that havefunction scope: they can be used (in a goto statement) anywhere in the same function in which they appear. There may be multiple labels before any statement.
Entering the scope of a non-variably modified variable is permitted: goto lab1;// OK: going into the scope of a regular variableint n=5;lab1:;// Note, n is uninitialized, as if declared by int n; // goto lab2; // Error: going into the scope of two VM typesdouble a[n];// a VLAint(*p)[n];// a VM pointerlab2: If {int n=1;label:;int a[n];// re-allocated 10 times, each with a different sizeif(n++<10)goto label;// leaving the scope of a VM} | (since C99) |
Because declarations are not statements, a label before a declaration must use a null statement (a semicolon immediately after the colon). Same applies to a label before the end of a block. | (until C23) |
C++ imposes additional limitations on thegoto statement, but allows labels before declarations (which are statements in C++).
#include <stdio.h> int main(void){// goto can be used to leave a multi-level loop easilyfor(int x=0; x<3; x++){for(int y=0; y<3; y++){printf("(%d;%d)\n",x,y);if(x+ y>=3)goto endloop;}}endloop:;}
Output:
(0;0)(0;1)(0;2)(1;0)(1;1)(1;2)
C++ documentation for goto statement |
