ZBasic System Library
281
ZBasic Microcontrollers
Type
Function returning Integer
Invocation
SetJmp(jmpbuf)
Parameter
Method
Type
Description
jmpbuf
ByRef
array of Byte
A buffer to hold the return context, see description below.
Discussion
This function, in conjunction with LongJmp(), provides a way to circumvent the normal call-return
structure and return directly to a distant caller. It is the equivalent of a non-local Goto function and can be
used, among other things, to handle exceptions in your programs. The parameter specifies a Byte array
that will be initialized with context information to allow a direct return from deeply nested calls. The array
must be a minimum size (either 6 bytes or 24 bytes for VM mode and native mode, respectively) to hold
the context information for unwinding the call stack. You can use the built-in constant
System.JumpBufSize to ensure that it is the proper size.
On the initial call to SetJmp() the return value will always be zero. When control is returned via a call to
LongJmp(), the return value will be the value supplied as the second parameter to the LongJmp() call.
Generally, you should choose this value to indicate the nature of the exception condition and in most
cases it should be non-zero.
The jump buffer needs to be accessible to the LongJmp() caller. Often, this is realized by making it a
global or module-level variable. If you want it to be a local variable, you’ll have to pass the buffer as a
parameter down the call chain. See the section on Exception Handling in the ZBasic Reference Manual
for more details.
Caution
If the provided array is less than minimum required size, adjacent memory locations will be modified
usually with undesirable results. Your application should not directly modify the contents of the array.
Doing so may cause unpredictable behavior.
Compatibility
This routine is not available in BasicX compatibility mode.
See Also
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