Docs » Autodocs » amiga.lib » CreateTask
CreateTask -- Create task with given name, priority, stacksize
task = CreateTask(name,pri,initPC,stackSize)
struct Task *CreateTask(STRPTR,LONG,funcEntry,ULONG);
This function simplifies program creation of sub-tasks by
dynamically allocating and initializing required structures
and stack space, and adding the task to Exec's task list
with the given name and priority. A tc_MemEntry list is provided
so that all stack and structure memory allocated by CreateTask()
is automatically deallocated when the task is removed.
An Exec task may not call dos.library functions or any function
which might cause the loading of a disk-resident library, device,
or file (since such functions are indirectly calls to dos.library).
Only AmigaDOS Processes may call AmigaDOS; see the
dos.library/CreateProc() or the dos.library/CreateNewProc()
functions for more information.
If other tasks or processes will need to find this task by name,
provide a complex and unique name to avoid conflicts.
If your compiler provides automatic insertion of stack-checking
code, you may need to disable this feature when compiling sub-task
code since the stack for the subtask is at a dynamically allocated
location. If your compiler requires 68000 registers to contain
particular values for base relative addressing, you may need to
save these registers from your main process, and restore them
in your initial subtask code.
The function entry initPC is generally provided as follows:
In C:
extern void functionName();
char *tname = "unique name";
task = CreateTask(tname, 0L, functionName, 4000L);
In assembler:
PEA startLabel
name - a null-terminated name string
pri - an Exec task priority between -128 and 127, normally 0
funcEntry - the address of the first executable instruction
of the subtask code
stackSize - size in bytes of stack for the subtask. Don't cut it
too close - system function stack usage may change.
task - a pointer to the newly created task, or NULL if there was not
enough memory.
Under exec.library V37 or beyond, the AddTask() function used
internally by CreateTask() can fail whereas it couldn't fail in
previous versions of Exec. Prior to amiga.lib V37.14, this function
did not check for failure of AddTask() and thus might return a
pointer to a task structure even though the task was not actually
added to the system.
Prior to amiga.lib V40.20 low memory conditions could cause
CreateTask() to malfunction. The implementation checked whether the
initial AllocEntry() call would fail, but would use an inappropriate
test condition.
DeleteTask(), exec.library/FindTask()
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