---
name: "setjmp"
section: "3avr"
platform: "linux"
package: "avr-libc"
version: "1:2.2.1-1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/setjmp/3avr"
---

# setjmp(3avr)

\<setjmp.h\>: Non-local goto

## NAME

setjmp - \<setjmp.h\>: Non-local goto

## SYNOPSIS

### Functions

int **setjmp** (jmp\_buf \_\_jmpb)\
 void **longjmp** (jmp\_buf \_\_jmpb, int \_\_ret)\

## Detailed Description

While the C language has the dreaded `goto` statement, it can only be used to jump to a label in the same (local) function. In order to jump directly to another (non-local) function, the C library provides the **setjmp** and **longjmp** functions. setjmp and longjmp are useful for dealing with errors and interrupts encountered in a low-level subroutine of a program.

**Note**

**setjmp** and **longjmp** make programs hard to understand and maintain. If possible, an alternative should be used.

longjmp can destroy changes made to global register variables (see **How to permanently bind a variable to a register?**).

For a very detailed discussion of setjmp/longjmp, see Chapter 7 of *Advanced Programming in the UNIX Environment*, by W. Richard Stevens.

Example:

```
#include <setjmp.h>
jmp_buf env;
int main (void)
{
    if (setjmp (env))
    {
        // Handle error ...
    }
    while (1)
    {
       // Main processing loop which calls foo() somewhere ...
    }
}
void foo (void)
{
    // blah, blah, blah ...
    if (err)
    {
        longjmp (env, 1);
    }
}
```

## Function Documentation

### void longjmp (jmp\_buf \_\_jmpb, int \_\_ret)` [extern]`

Non-local jump to a saved stack context.

```
#include <setjmp.h>
```

**longjmp()** restores the environment saved by the last call of **setjmp()** with the corresponding *\_\_jmpb* argument. After **longjmp()** is completed, program execution continues as if the corresponding call of **setjmp()** had just returned the value *\_\_ret*.

**Note**

**longjmp()** cannot cause 0 to be returned. If **longjmp()** is invoked with a second argument of 0, 1 will be returned instead.

**Parameters**

*\_\_jmpb* Information saved by a previous call to **setjmp()**. \
 *\_\_ret* Value to return to the caller of **setjmp()**.

**Returns**

This function never returns.

### int setjmp (jmp\_buf \_\_jmpb)` [extern]`

Save stack context for non-local goto.

```
#include <setjmp.h>
```

**setjmp()** saves the stack context/environment in *\_\_jmpb* for later use by **longjmp()**. The stack context will be invalidated if the function which called **setjmp()** returns.

**Parameters**

*\_\_jmpb* Variable of type `jmp_buf` which holds the stack information such that the environment can be restored.

**Returns**

**setjmp()** returns 0 if returning directly, and non-zero when returning from **longjmp()** using the saved context.

## Author

Generated automatically by Doxygen for AVR-LibC from the source code.