Common Anchor Area

Each thread is represented by a common anchor area (CAA), which is the central communication area for Language Environment. All thread- and enclave-related resources are anchored, provided for, or can be obtained through the CAA. The CAA is generated during thread initialization and deleted during thread termination. When calling Language Environment-conforming routines, register 12 points to the address of the CAA.

Use CAA fields as described. Do not modify fields and do not use routine addresses as entry points, except as specified. Fields marked ‘Reserved’ exist for migration of specific languages, or internal use by Language Environment. Language Environment defines their location in the CAA, but not their use. Do not use or reference them except as specified by the language that defines them.

Table 1 describes the CAA fields. For more information about the CAA and other structures to which it refers (for example, the DLL failure control block, CEEDLLF), see z/OS Language Environment Vendor Interfaces.

Table 1. Description of CAA fields
Hex Offset	Type	Len	CAA Field	Explanation
0	Bit	1	CEECAAFLAG0	CAA flag bits, defined as follows: 0–5 Reserved 6 CEECAAXHDL. A flag used by the condition handler. If the flag is set to 1, the application requires immediate return/percolation to the system on any interrupt or condition handler event. 7 Reserved
1	Bit	1	Reserved
2	Bit	1	CEECAALANGP	PL/I language compatibility flags external to Language Environment. The bits are defined as follows: 0–3 Reserved 4 CEECAATHFN. A flag set by PL/I to indicate a PL/I FINISH ON-unit is active. If the flag is set to 1, no PL/I FINISH ON-unit is active. If the flag is set to 0, a PL/I FINISH ON-unit could be active. 5–7 Reserved
3	Char	5	Reserved
8	Address	4	CEECAABOS	Start of the current storage segment. This field is initially set during thread initialization. It indicates the start of the current stack storage segment. It is altered when the current stack storage segment is changed.
C	Address	4	CEECAAEOS	This field is used to determine if a stack overflow routine must be called when allocating storage from the user stack. Normally, the value of this field will represent the end of the current user stack segment. However, its value can also be zero to force the call of a stack overflow routine for every allocation of storage from the user stack. This field is used by function prologs that do not use FASTLINK linkage conventions.
10	Char	52	Reserved
44	Signed	2	CEECAATORC	Thread level return code. The thread level return code set by CEESRC callable service.
46	Signed	2	CEECAATURC
48	Char	44	Reserved
74	Address	4	CEECAATOVF	Address of stack overflow routine.
78	Char	168	Reserved
120	Address	4	CEECAAATTN	Address of the Language Environment attention handling routine. The address of the Language Environment attention handling routine supports common run-time environment’s polling code convention for attention processing.
124	Char	56	Reserved
15C	Address	4	CEECAAHLLEXIT	Address of the Exit List Control Block set by the HLL user exit CEEBINT.
160	Char	56	Reserved
198	Bit (96)	12	CEECAAHOOK	Code to pass control to the debugger.
1A4	Address	4	CEECAADIMA	A(debugger entry)
1A8	Char	68	CEECAAHOOKS	Hook area. This is the start of 18 fullword execute hooks. Language Environment initializes each fullword to X'07000000'. The hooks can be altered to support various debugging hook mechanisms.
1A8	Char	4	CEECAAALLOC	ALLOCATE descr. built
1AC	Char	4	CEECAASTATE	New statement begins
1B0	Char	4	CEECAAENTRY	Block entry
1B4	Char	4	CEECAAEXIT	Block exit
1B8	Char	4	CEECAAMEXIT	Multiple block exit
1BC	Char	32	CEECAAPATHS	PATH hooks
1BC	Char	4	CEECAALABEL	At a label constant
1C0	Char	4	CEECAABCALL	Before CALL
1C4	Char	4	CEECAAACALL	After CALL
1C8	Char	4	CEECAADO	DO block starting
1CC	Char	4	CEECAAIFTRUE	True part of IF
1D0	Char	4	CEECAAIFFALSE	False part of IF
1D4	Char	4	CEECAAWHEN	WHEN group starting
1D8	Char	4	CEECAAOTHER	OTHERWISE group
1DC	Char	4	CEECAACGOTO	GOTO hook for C
1E0	Char	4	CEECAARSVDH1	Reserved hook
1E4	Char	4	CEECAARSVDH2	Reserved hook
1E8	Char	4	CEECAAMULTEVT	Multiple Event Hook
1EC	Bit (32)	4	CEECAAMEVMASK	Muliple Event Hook Mask -End of Debug
1F0	Char	80	CEECAAMEMBER_AREA
1F0	Address	4	CEECAACGENE	C/370™ CGENE
1F4	Address	4	CEECAACRENT	C/370 writable static
1F8	Char	8	CEECAACFLTINIT	Used to convert fixed to float cfltini
200	Address	4	CEECAACPRMS	Address of parameters passed to main module
204	Signed	4	CEECAAC_RTL	Combination of 24 unique C/370 trc typ
208	Address	4	CEECAACTHD
20C	Address	4	CEECAACURRFECB
210	Address	4	CEECAAEDCV	C/370 vector table
214	Address	4	CEECAACPCB	Reserved
218	Address	4	CEECAACEDB	C/370 CEDB
21C	Char	3	Reserved
21F	Char	1	CEECAASPCFLAG3	Used for SPC
220	Address	4	CEECAACIO	Address of cio
224	Char	4	CEECAAFDSETFD	Used by FD_* macros
228	Char	2	CEECAAFCBMUTEXOK
22A	Char	2	Reserved
22C	Char	4	CEECAATC16
230	Signed	4	CEECAATC17
234	Address	4	CEECAAEDCOV	C/370 Open Libvec
238	Signed	4	CEECAACTOFSV
23C	Address	4	CEECAATRTSPACE	C/370 Open Libvec
240	Char	24	Reserved
258	Address	4	CEECAA_TCASRV_USERWORD	TCA Service Rtn Vctr
25C	Address	4	CEECAA_TCASRV_WORKAREA
260	Address	4	CEECAA_TCASRV_GETMAIN
264	Address	4	CEECAA_TCASRV_FREEMAIN
268	Address	4	CEECAA_TCASRV_LOAD
26C	Address	4	CEECAA_TCASRV_DELETE
270	Address	4	CEECAA_TCASRV_EXCEPTION
274	Address	4	CEECAA_TCASRV_ATTENTION
278	Address	4	CEECAA_TCASRV_MESSAGE
27C	Char	4	Reserved
280	Address	4	CEECAALWS	Addr of PL/I LWS
284	Address	4	CEECAASAVR	Register save
288	Char	36	Reserved
2AC	Bit	1	CEECAASYSTM	Underlying operating system. The value indicates the operating system supporting the active environment. 0 Undefined. This value should not appear after Language Environment is initialized. 1 Unsupported 3 z/OS
2AD	Bit (8)	1	CEECAAHRDWR	Underlying hardware. This value indicates the type of hardware on which the routine is running. 0 Undefined. This value should not appear after Language Environment is initialized. 1 Unsupported 2 System/370, non-XA 3 System/370, XA 4 System/370, ESA
2AE	Bit (8)	1	CEECAASBSYS	Underlying subsystem. This value indicates the subsystem (if any) on which the routine is running. 0 Undefined. This value should not occur after Language Environment is initialized. 1 Unsupported 2 None. The routine is not running under a Language Environment-recognized subsystem. 3 TSO 4 IMS™ 5 CICS®
2AF	Bit (8)	1	CEECAAFLAG2	CAA Flag 2, defined as follows: 0 Bimodal addressing is available. 1 Vector hardware is available. 2 Thread terminating. 3 Initial thread 4 Library trace is active. The TRACE runtime option was set. 5 Reserved 6 CEECAA_ENQ_Wait_Interruptible. Thread is in an enqueue wait. 7 Reserved
2B0	Unsign	1	CEECAALEVEL	Language Environment level identifier. This contains a unique value that identifies each release of Language Environment. This number is incremented for each new release of Language Environment.
2B1	Bit (8)	1	CEECAA_PM	Image of current program mask.
2B2	Bit (16)	2	CEECAA_INVAR	Field that is at the same fixed offset in 31-bit and 64-bit CAAs
2B3	Bit	1	Reserved
2B4	Address	4	CEECAAGETLS	Address of stack overflow for library routines.
2B8	Address	4	CEECAACELV	Address of the Language Environment library vector. This field is used to locate dynamically loaded Language Environment routines.
2BC	Address	4	CEECAAGETS	Address of the Language Environment prolog stack overflow routine. The address of the Language Environment get stack storage routine is included in prolog code for fast reference.
2C0	Address	4	CEECAALBOS	Start of the library stack storage segment. This field is initially set during thread initialization. It indicates the start of the library stack storage segment. It is altered when the library stack storage segment is changed.
2C4	Address	4	CEECAALEOS	This field is used to determine if a stack overflow routine must be called when allocating storage from the library stack. Normally, the value of this field will represent the end of the current library stack segment. However, its value can also be zero to force the call of a stack overflow routine for every allocation of storage from the library stack. This field is used by function prologs that do not use FASTLINK linkage conventions.
2C8	Address	4	CEECAALNAB	Next available library stack storage byte. This contains the address of the next available byte of storage on the library stack. It is modified when library stack storage is obtained or released.
2CC	Address	4	CEECAADMC	Language Environment shunt routine address. Its value is initially set to 0 during thread initialization. If it is nonzero, this is the address of a routine used in specialized exception processing.
2D0	Signed	4	CEECAAACD	Most recent CAASHAB abend code.
2D0	Signed	4	CEEAAABCODE	Most recent abend completion code.
2D4	Signed	4	CEECAAARS	Most recent CAASHAB reason code.
2D4	Signed	4	CEECAAARSNCODE	Most recent abend reason code.
2D8	Address	4	CEECAAERR	Address of the current condition information block. After completion of initialization, this always points to a condition information block. During exception processing, the current condition information block contains information about the current exception being processed. Otherwise, it indicates no exception being processed.
2DC	Address	4	CEECAAGETSX	Address of the user stack extender routine. This routine is called to extend the current stack frame in the user stack. Its address is in the CEECAA for performance reasons.
2E0	Address	4	CEECAADDSA	Address of the Language Environment dummy DSA. This address determines whether a stack frame is the dummy DSA, also known as the zeroth DSA.
2E4	Signed	4	CEECAASECTSIZ	Vector section size. This field is used by the vector math services.
2E8	Signed	4	CEECAAPARTSUM	Vector partial sum number. This field is used by the vector math services.
2EC	Signed	4	CEECAASSEXPNT	Log of the vector section size. This field is used by the vector math services.
2F0	Address	4	CEECAAEDB	Address of the Language Environment EDB. This field points to the encompassing EDB.
2F4	Address	4	CEECAAPCB	Address of the Language Environment PCB. This field points to the encompassing PCB.
2F8	Address	4	CEECAAEYEPTR	Address of the CAA eye catcher. The CAA eye catcher is CEECAA. This field can be used for validation of the CAA.
2FC	Address	4	CEECAAPTR	Address of the CAA. This field points to the CAA itself and can be used in validation of the CAA.
300	Address	4	CEECAAGETS1	Non-DSA stack overflow. This field is the address of a stack overflow routine, which cannot guarantee that the current register 13 is pointing at a stack frame. Register 13 must point, at a minimum, to a save area.
304	Address	4	CEECAASHAB	ABEND shunt routine. Its value is initially set to zero during thread initialization. If it is nonzero, this is the address of a routine used in specialized exception processing for ABENDs that are intercepted in the ESTAE exit.
308	Address	4	CEECAAPRGCK	Routine interrupt code for CEECAADMC. If CEECAADMC is nonzero, and a routine interrupt occurs, this field is set to the routine interrupt code and control is passed to the address in CEECAAMDC.
30C	Bit (8)	1	CEECAAFLAG1	CAA flag bits, defined as follows: 0 CEECAASORT. A call to DFSORT is active. 1 CEECAA_USE_OLD_STK. Use the old stack. 2 CEECAA_CICS_EXT_REG . ERTLI CICS extended register interface is in effect 3 CEECAASHAB_RECOVER_IN_ESTAE _MODE. When on, the Language Environment® ESTAE resumes to the abend shunt in the mode and key in which the Language Environment ESTAE was established 4–7 Reserved.
30D	Char	1	CEECAASHAB_KEY	IPK result when CEECAASHAB is set.
30E	Char	2	Reserved
310	Signed	4	CEECAAURC	Thread level return code. This is the common place for members to set the return codes for subroutine-to-subroutine return code processing.
314	Address	4	CEECAAESS	Determine if a stack overflow routine must be called when allocating storage from the user stack. Normally, the value of this field will represent the end of the current user stack segment. However, its value can also be zero to force the call of a stack overflow routine for every allocation of storage from the user stack. This field is used by function prologs that use FASTLINK linkage conventions.
318	Address	4	CEECAALESS	Determine if a stack overflow routine must be called when allocating storage from the library stack. Normally, the value of this field will represent the end of the current library stack segment. However, its value can also be zero to force the call of a stack overflow routine for every allocation of storage from the library stack. This field is used by function prologs that use FASTLINK linkage conventions.
31C	Address	4	CEECAAOGETS	Overflow from user stack allocations.
320	Address	4	CEECAAOGETLS	Overflow from library stack allocations.
324	Address	4	CEECAAPICICB	Address of the preinitialization compatibility control block.
328	Address	4	CEECAAOGETSX	User DSA exit from OPLINK.
32C	Signed	2	CEECAAGOSMR	Go some more—Used CEEHTRAV multiple.
32E	Signed	2	Reserved
330	Address	4	CEECAALEOV	This field is the address of the Language Environment library vector for z/OS UNIX support.
334	Signed	4	CEECAA_SIGSCTR	SIGSAFE counter.
338	Bit (32)	4	CEECAA_SIGSFLG	SIGSAFE flags indicate the signal safety of the library and are defined, as follows. 0 CEECAA_SIGPUTBACK. The signal cannot be delivered, therefore the signal is put back to the kernel. 1 CEECAA_SA_RESTART. Indicates that a signal registered with the SA_RESTART flag interrupted the last kernel call, and the signal catcher returned. 2 Reserved 3 CEECAA_SIGSAFE. It is safe to deliver the signal, while in library code. 4 CEECAA_CANCELSAFE. It is safe to deliver the cancel signal, while in library code. 5 CEECAA_SIGRESYNCH. CEECAA_sigputsynch flag was on last time CEEOSIGR resolicited a signal. 6 CEECAA_FRZ_UNSAFE. This thread is in an unsafe state to be frozen. 7 CEECAA_NOAPPREGS. User application registers may be saved in a nonstandard place. 8 CEECAA_EINTR_RSOL. Secondary Signal resolicitation is in progress, after EINTR errno from inner function. 9 CEECAA_EINTR_PUTB. Secondary resolicited signal has been put back. 10 CEECAA_EINTR_REST. User signal catcher returned after catching secondary resolicited signal with SA_RESTART in effect. 11 CEECAA_EINTR_SIGG. Stray signal interrupted CEEOSIGG while secondary signal resolicitation was in progress.
33A	Bit (16)	2	Reserved
33C	Char	8	CEECAATHDID	This field is the thread identifier
344	Address	4	CEECAA_DCRENT	Reserved
348	Address	4	CEECAA_DANCHOR	Reserved
34C	Address	4	CEECAA_CTOC	TOC anchor for CRENT.
354	Signed	4	CEECAACICSRSN	CICS reason code from member language.
358	Address	4	CEECAAMEMBR	Address of thread-level member list.
35C	Address	4	CEECAA_SIGNAL_STATUS	Signal status of the terminating thread member list.
360	Address	4	CEECAA_HCOM_REG7	HCOM saved R7.
360	Address	4	CEECAA_HCOM_REG14	HCOM saved R14.
364	Address	4	CEECAA_STACKFLOOR	Lowest usable address in XP stack.
368	Address	4	CEECAAHPGETS	XP stack extension rtn.
36C	Address	4	CEECAAEDCHPXV	C/C++ XPLINK libvec.
370	Address	4	CEECAAFOR1	Reserved for FORTRAN.
374	Address	4	CEECAAFOR2	Reserved for FORTRAN.
378	Address	4	CEECAATHREADHEAPID	Thread heap ID.
37C	Signed	4	CEECAA_SYS_RTNCODE	System (kernel) return code.
380	Signed	4	CEECAA_SYS_RSNCODE	System (kernel) reason code.
384	Address	4	CEECAAGETFN	Address of the WSA swap routine.
388	Address	4	CEECAA_JIT1	Reserved.
38C	Address	4	CEECAA_JIT2	Reserved.
390	Address	4	CEECAASIGNGPTR	Pointer to 'signam’ external variable in a C application.
394	Signed	4	CEECAASIGNG	Value of sign of lgamma() -1 - negative sign 0 - zero +1 - positive sign.
398	Address	4	CEECAA_FORDBG	Ptr to AFHDBHIM - FORTRAN hook interface.
39C	Bit (8)	1	CEECAAAB_STATUS	Validity flags.
39D	Unsign	1	CEECAA_STACKDIRECTION	Stack direction.
39E	Bit	2	Reserved
3A0	Signed	4	CEECAAAB_GR0	Reg 0 at the time of abend.
3A4	Signed	4	CEECAAAB_ICD1	SDWAICD1.
3A8	Signed	4	CEECAAAB_ABCC	SDWAABCC.
3AC	Signed	4	CEECAAAB_CRC	SDWACRC.
3B0	Address	4	CEECAAAGTS	Entry point of CEEVAGTS routine.
3B4	Address	4	CEECAA_LER5N1	Reserved.
3B8	Address	4	CEECAAHERP	Address of CEEHERP routine.
3BC	Address	4	CEECAAUSTKBOS	Start of user stack segment.
3C0	Address	4	CEECAAUSTKEOS	End of user stack segment.
3C4	Address	4	CEECAAUSERRTN@	Address of thread start routine. Undefined on IPT or prior to thread init event.
3C8	Bit	8	CEECAAUDHOOK	Hook swapping XPLINK.
3D0	Address	4	CEECAACEL_HPXV_B	Address of XPLINK compat vector for Base library.
3D4	Address	4	CEECAACEL_HPXV_M	Address of XPLINK compat vector for Math library.
3D8	Address	4	CEECAACEL_HPXV_L	Address of XPLINK compat vector for Locale library.
3DC	Address	4	CEECAACEL_HPXV_O	Address of XPLINK compat vector for Open library.
3E0	Address	4	CEECAACEL4VEC3	Address of 3rd C-RTL library vector.
3E4	Address	4	CEECAA_CEEDLLF	Address of the newest CEEDLLF control block.
3E8	Address	4	CEECAA_SAVSTACK	Zero or saved stack pointer. This field can be used to save the stack pointer before calling a routine with OS_NOSTACK linkage. After the call returns, this field must be set back to zero.
3EC	Char	4	Reserved
3F0	Char	4	CEECAA_USER_WORD	4-byte user field available for application use. In pre-initialization (CEEPIPI) environments, this field is initialized in the IPT CAA from the CEEPIPI set_user_word function. This field is initialized to 0 in non-CEEPIPI environments (including all nested enclaves), and for all non-IPT CAAs in CEEPIPI environments. This field is not otherwise accessed by Language Environment.
3F4	Address	4	CEECAA_SAVSTACK_ASYNC	Zero or address of field that is zero or saved stack pointer. An application that has large sections of code that do not require access to the Language Environment stack but could benefit from having an additional register available can use this field.