What is longjmp function?

setjmp and longjmp are a pair of C function facilitating cross-procedure transfer of control. Typically they are used to allow resumption of execution at a known good point after an error. Both take as first argument a buffer, which is used to hold the machine state at the jump destination.

What is the use of setjmp and longjmp?

When setjmp and longjmp are used together, they provide a way to execute a non-local goto . They are typically used in C code to pass execution control to error-handling or recovery code in a previously called routine without using the standard calling or return conventions.

Does longjmp unwind stack?

When a “non-local goto” is executed via setjmp / longjmp in C++, normal “stack unwinding” does not occur. Calling longjmp restores the stack pointer, which—because the function returned—would point to a non-existent and potentially overwritten or corrupted stack frame.

What does setjmp return?

So, when you call setjmp(), you pass it the address of an array of integers, and it stores the value of the registers in that array. Setjmp() returns 0 when you call it in this way.

When to use setjmp / longjmp in Java?

In my experience in most cases whenever you think that using setjmp / longjmp would work, your program is clear and simple enough that every intermediate function call in the call chain can do error handling, or it’s so messy and impossible to fix that you should do exit when you encounter the error.

What is the purpose of the longjmp function?

The longjmp function restores a stack environment and execution locale previously saved in env by setjmp. setjmp and longjmp provide a way to execute a nonlocal goto; they are typically used to pass execution control to error-handling or recovery code in a previously called routine without using the normal call and return conventions.

Where does the error handling code go in Visual Basic?

Here, the error-handling code follows the Exit Sub statement and precedes the End Sub statement to separate it from the procedure flow. You can place error-handling code anywhere in a procedure. Untrapped errors in objects are returned to the controlling application when the object is running as an executable file.

Is it safe to use longjmp in C + +?

In Microsoft C++ code on Windows, longjmp uses the same stack-unwinding semantics as exception-handling code. It is safe to use in the same places that C++ exceptions can be raised. However, this usage is not portable, and comes with some important caveats.