OS/2 defines a class of error conditions called system exceptions, and specifies the default actions that are taken when these system exceptions occur. The default action taken by OS/2 in most cases is to terminate the thread that caused the system exception.
System exceptions include both synchronous and asynchronous exceptions. Synchronous exceptions are caused by events that are internal to the execution of a thread. For example, synchronous exceptions could be caused by invalid parameters, or by the request of a thread to end its own execution.
Asynchronous exceptions are caused by events that are external to the execution of a thread. For example, an asynchronous exception can be caused by a user entering a Ctrl+C or Ctrl+Break key sequence, or by a process calling DosKillProcess to end the execution of another process.
The Ctrl+Break, Ctrl+C, and DosKillProcess-generated exceptions are also known as signals, or as signal exceptions.
OS/2 delivers exceptions that occur in 16-bit as well as 32-bit code. The sequence or hierarchy for delivering exceptions is as follows:
Notification of an exception is usually sent only to the thread that caused the exception. However, if a thread uses DosExit to terminate all the threads in the process, notification of the process-termination exception is sent to every thread in the process. The thread that used DosExit gets a XCPT_PROCESS_TERMINATE exception, all the other threads in the process get a XCPT_ASYNC_PROCESS_TERMINATE exception.
Exit-list processing occurs on a per-process basis after a process-termination exception has been delivered to each thread in the process and each thread has finally ended except Thread 1 (the main thread). Therefore, any thread that handles a process-termination exception must eventually end its own execution voluntarily. Otherwise, the process-termination sequence will not conclude properly.
The following tables briefly list the possible exceptions. For more detailed information about the system exceptions, including default system action, parameters, and related trap numbers, see the Control Program Programming Reference.
Non-Fatal, Software-Generated Exceptions
旼컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컫컴컴컴컴컴컴컴컴컴컴컴엿Exception Symbolic Constant 쿏escription � 쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴� 쿦CPT_GUARD_PAGE_VIOLATION 쿌 guard page has been � � 쿪ccessed. � 쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴� 쿦CPT_UNABLE_TO_GROW_STACK 쿟he system is unable � � 퀃o allocate the memory� � 쿾age directly below � � 퀃he guard page just � � 쿪ccessed. � 읕컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컨컴컴컴컴컴컴컴컴컴컴컴�
Fatal, Software-Generated Exceptions
旼컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컫컴컴컴컴컴컴컴컴컴컴컴� 쿐xception Symbolic Constant 쿏escription � 쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴� 쿦CPT_IN_PAGE_ERROR 쿌n I/O error occurred � � 퀇hile reading a memory� � 쿾age into memory. � 쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴� 쿦CPT_PROCESS_TERMINATE 쿟he thread has � � 퀃erminated itself with� � �DosExit. � 쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴� 쿦CPT_ASYNC_PROCESS_TERMINATE 쿌nother thread in the � � 쿾rocess has caused the� � 퀃hread to terminate. � 쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴� 쿦CPT_NONCONTINUABLE_EXCEPTION 쿌n exception handler � � 쿴as attempted to � � 쿬ontinue execution in � � 퀁esponse to a � � 쿻on-continuable � � 쿮xception. � 쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴� 쿦CPT_INVALID_DISPOSITION 쿌n exception handler � � 쿴as returned an � � 쿶nvalid value. � 읕컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컨컴컴컴컴컴컴컴컴컴컴컴�
Fatal, Hardware-Generated Exceptions
旼컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컫컴컴컴컴컴컴컴컴컴컴컴� 쿐xception Symbolic Constant 쿏escription � 쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴� 쿦CPT_ACCESS_VIOLATION 쿌n access violation or� � 쿾age fault has � � 쿽ccurred. � 쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴� 쿦CPT_INTEGER_DIVIDE_BY_ZERO 쿌n attempt to divide � � 쿫y 0 has occurred in � � 쿪n integer operation. � 쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴� 쿦CPT_FLOAT_DIVIDE_BY_ZERO 쿌n attempt to divide � � 쿫y 0 has occurred in a� � 쿯loating point � � 쿽peration. � 쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴� 쿦CPT_FLOAT_INVALID_OPERATION 쿌n invalid floating � � 쿾oint operation was � � 쿪ttempted. � 쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴� 쿦CPT_ILLEGAL_INSTRUCTION 쿌n attempt was made to� � 쿮xecute an instruction� � 퀃hat is not defined on� � 퀃he host machine's � � 쿪rchitecture. � 쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴� 쿦CPT_PRIVILEGED_INSTRUCTION 쿌n attempt was made to� � 쿮xecute an instruction� � 퀃hat is not permitted � � 쿶n the current machine� � 쿺ode or that the � � 쿪pplication does not � � 쿴ave permission to � � 쿮xecute. � 쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴� 쿦CPT_INTEGER_OVERFLOW 쿌n integer operation � � 쿲enerated a carry-out � � 쿽f the most � � 퀂ignificant bit. � 쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴� 쿦CPT_FLOAT_OVERFLOW 쿌 floating point � � 쿽peration generated a � � 퀁esulting exponent � � 퀃hat is greater than � � 퀃he magnitude � � 쿾ermitted for the � � 쿽perands. � 쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴� 쿦CPT_FLOAT_UNDERFLOW 쿌 floating point � � 쿽peration generated a � � 퀁esulting exponent � � 퀃hat is less than the � � 쿺agnitude provided for� � 퀃he operands. � 쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴� 쿦CPT_FLOAT_DENORMAL_OPERAND 쿌n attempt was made to� � 쿾erform an arithmetic � � 쿽peration on a � � 쿭enormal operand. � 쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴� 쿦CPT_FLOAT_INEXACT_RESULT 쿟he result of an � � 쿽peration is not � � 쿮xactly representable � � 쿶n the target format. � 쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴� 쿦CPT_FLOAT_STACK_CHECK 쿌n illegal stack � � 쿽peration was � � 쿪ttempted by the � � 쿯loating point � � 쿬oprocessor. � 쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴� 쿦CPT_DATATYPE_MISALIGNMENT 쿌n attempt was made to� � 퀂tore a data in an � � 쿪ddress that is not � � 쿻aturally aligned on a� � 쿴ardware architecture � � 퀃hat does not provide � � 쿪lignment hardware. � 쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴� 쿦CPT_BREAKPOINT 쿌 breakpoint � � 쿶nstruction was � � 쿮xecuted. � 쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴� 쿦CPT_SINGLE_STEP 쿚ne instruction has � � 쿫een executed in � � 퀂ingle-step mode. � 읕컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컨컴컴컴컴컴컴컴컴컴컴컴�
Fatal Exceptions
旼컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컫컴컴컴컴컴컴컴컴컴컴컴� 쿐xception Symbolic Constant 쿏escription � 쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴� 쿦CPT_INVALID_LOCK_SEQUENCE 쿌n invalid operation � � 퀇as attempted within � � 쿪n interlocked section� � 쿽f code. � 쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴� 쿦CPT_ARRAY_BOUNDS_EXCEEDED 쿌n array index outside� � 쿶ts upper and lower � � 쿫oundary was detected.� 읕컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컨컴컴컴컴컴컴컴컴컴컴컴�
Unwind Operation Exceptions
旼컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컫컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿐xception Symbolic Constant 쿏escription � 쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿦CPT_UNWIND 쿌n unwind operation is in � � 쿾rocess. � 쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿦CPT_BAD_STACK 쿌n � � �EXCEPTIONREGISTRATIONRECORD � � 쿭ata structure was reached � � 퀃hat is not properly aligned� � 쿽r that is not within the � � 쿬urrent stack boundaries. � 쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 쿦CPT_INVALID_UNWIND_TARGET 쿟he address of the target � � �EXCEPTIONREGISTRATIONRECORD � � 쿶s below the current stack � � 쿾ointer or not in the � � 쿮xception handler chain. � 읕컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컨컴컴컴컴컴컴컴컴컴컴컴컴컴컴�
Fatal Signal Exceptions
旼컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컫컴컴컴컴컴컴컴컴컴컴컴� 쿐xception Symbolic Constant 쿏escription � 쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컵컴컴컴컴컴컴컴컴컴컴컴� 쿦CPT_SIGNAL 쿌 signal was made to � � 퀉our process (usually � � 퀃o stop). All the � � 퀂ignal exceptions � � �(Ctrl+Break, Ctrl+C, � � 쿪nd � � 쿦CPT_SIGNAL_KILLPROC) � � 쿬ome under this � � 쿮xception. � 읕컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컨컴컴컴컴컴컴컴컴컴컴컴�