unwind.5 (2010 09)

unwind(5) unwind(5)

(Itanium(R)-based Systems Only)

_UNW_MEMORY_ALLOCATION_ERROR

in the event of a low memory condition.

Low Memory Conditions

In most cases, a failed construction of an

_Unwind_Context leaves the client with enough of an

_Unwind_Context

object to support a call to the function _UNW_getAlertCode()

, which would

return

_UNW_MEMORY_ALLOCATION_ERROR

in the event of a failed construction. Had the construction

been successful,

_UNW_getAlertCode()

would have returned _UNW_OK

. Failed construction is

sometimes communicated by setting the

_Unwind_Context

pointer to NULL. Subsequent calls to stack

unwind library interface functions return

_UNW_MEMORY_ALLOCATION_ERROR

if the

_Unwind_Context

pointer is NULL.

A failed memory allocation during actions such as

_UWN_step() returns the

_UNW_MEMORY_ALLOCATION_ERROR

return code and sets the _Unwind_Context

Alert Code. The

remaining state of

_Unwind_Context

is undeﬁned.

Return Code Semantics

The enumeration

_UNW_ReturnCode

has some embedded semantics. _UNW_OK has value 0. Stack

boundary conditions that indicate stack frames through which the stack unwind library cannot step are

assigned negative values. For example,

_UNW_STEP_BOTTOM

and

_UNW_STEP_KERNEL_SAVE_STATE

have negative values. All other return values in the enumeration

have positive values. Hewlett-Packard reserves the right to add more return codes to the enumeration.

For compatibility reasons, none will be removed, nor will the values assigned to existing return codes be

changed in future releases.