setjmp

 

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setjmp
longjmp
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jmp_buf

 

Defined in header <csetjmp>
#define setjmp(env) /* implementation-defined */

Saves the current execution context into a variable env of type std::jmp_buf. This variable can later be used to restore the current execution context by std::longjmp function. That is, when a call to std::longjmp function is made, the execution continues at the particular call site that constructed the std::jmp_buf variable passed to std::longjmp. In that case setjmp returns the value passed to std::longjmp.

Parameters

env

-

variable to save the execution state of the program to.

Return value

​0​ if the macro was called by the original code and the execution context was saved to env.

Non-zero value if a non-local jump was just performed. The return value in the same as passed to std::longjmp.

Example

run this code

#include <iostream>
#include <csetjmp>
 
std::jmp_buf jump_buffer;
 
[[noreturn]] void a(int count) 
{
    std::cout << "a(" << count << ") called\n";
    std::longjmp(jump_buffer, count+1);  // setjump() will return count+1
}
 
int main()
{
    int count = setjmp(jump_buffer);
    if (count != 9) {
        a(count);  // This will cause setjmp() to exit
    }
}

Output:

a(0) called
a(1) called
a(2) called
a(3) called
a(4) called
a(5) called
a(6) called
a(7) called
a(8) called

See also

longjmp	jumps to specified location (function)