HP OpenVMS System Services Reference Manual

$IEEE_SET_FP_CONTROL (Alpha and I64)

On Alpha and I64 systems, modifies IEEE floating-point state and, optionally, returns the previous value.
The service provides the mechanism to set the specified state bits, to clear the specified state bits, and to swap one set of state bits for another.

Format

SYS$IEEE_SET_FP_CONTROL [clrmsk] ,[setmsk] ,[prvmsk]

C Prototype

int sys$ieee_set_fp_control (struct _ieee *clrmsk, struct _ieee *setmsk, struct _ieee *prvmsk);

Arguments

clrmsk

OpenVMS usage: mask_quadword

type: quadword (unsigned)

access: read only

mechanism: by reference

Address of a quadword bit mask to be cleared in the IEEE floating-point control register.
The $IEEEDEF macro defines symbols for the floating-point control register. Table SYS-47 shows the symbols, their corresponding masks, and their meaning:

Table SYS-47 Format of the IEEE Floating-Point Control Register (Alpha and I64)
Symbol Mask Meaning

IEEE$M_TRAP_ENABLE_INV 2 Enable invalid operation exception

IEEE$M_TRAP_ENABLE_DZE 4 Enable divide by 0 exception

IEEE$M_TRAP_ENABLE_OVF 8 Enable overflow exception

IEEE$M_TRAP_ENABLE_UNF 10 Enable underflow exception

IEEE$M_TRAP_ENABLE_INE 20 Enable inexact exception

IEEE$M_TRAP_ENABLE_DNOE 40 Enable denormal operand exception

IEEE$M_MAP_DNZ 2000 Denormal operands are mapped to 0.0

IEEE$M_MAP_UMZ 4000 Underflow results are mapped to 0.0

IEEE$M_INHERIT 8000 Inherit FP state on thread create

IEEE$M_STATUS_INV 20000 Invalid operation

IEEE$M_STATUS_DZE 40000 Divide by 0

IEEE$M_STATUS_OVF 80000 Overflow

IEEE$M_STATUS_UNF 100000 Underflow

IEEE$M_STATUS_INE 200000 Inexact

IEEE$M_STATUS_DNO 400000 Denormal operand

setmsk

OpenVMS usage: mask_quadword

type: quadword (unsigned)

access: read only

mechanism: by reference

Address of a quadword bit mask to be set in the IEEE floating-point control register.
Table SYS-47 shows the format of the IEEE floating-point control register.
prvmsk

OpenVMS usage: mask_quadword

type: quadword (unsigned)

access: write only

mechanism: by reference

Address of a quadword to receive the previous value of the IEEE floating-point control register.

**Table SYS-47 Format of the IEEE Floating-Point Control Register (Alpha and I64)**
Symbol	Mask	Meaning
IEEE$M_TRAP_ENABLE_INV	2	Enable invalid operation exception
IEEE$M_TRAP_ENABLE_DZE	4	Enable divide by 0 exception
IEEE$M_TRAP_ENABLE_OVF	8	Enable overflow exception
IEEE$M_TRAP_ENABLE_UNF	10	Enable underflow exception
IEEE$M_TRAP_ENABLE_INE	20	Enable inexact exception
IEEE$M_TRAP_ENABLE_DNOE	40	Enable denormal operand exception
IEEE$M_MAP_DNZ	2000	Denormal operands are mapped to 0.0
IEEE$M_MAP_UMZ	4000	Underflow results are mapped to 0.0
IEEE$M_INHERIT	8000	Inherit FP state on thread create
IEEE$M_STATUS_INV	20000	Invalid operation
IEEE$M_STATUS_DZE	40000	Divide by 0
IEEE$M_STATUS_OVF	80000	Overflow
IEEE$M_STATUS_UNF	100000	Underflow
IEEE$M_STATUS_INE	200000	Inexact
IEEE$M_STATUS_DNO	400000	Denormal operand

Description

The Set IEEE Floating-Point Control Register service updates the IEEE floating-point control register, maintained by the operating system, with the values supplied by the calling program.
The following steps are used to update the register:

If the prvmsk argument is specified, $IEEE_SET_FP_CONTROL first reads the previous value of the IEEE floating-point control register.
If the clrmsk argument is specified, $IEEE_SET_FP_CONTROL then clears the specified bit masks in the clrmsk argument.
If the setmsk argument is specified, $IEEE_SET_FP_CONTROL then sets the specified bit masks in the setmsk argument.

A program can swap the IEEE floating-point control register (that is, save the old value and specify a new value) by specifying the following:

The clrmsk argument with the address of a quadword of all 1s
The setmsk argument with the address of a quadword that holds the new register value
The prvmsk argument with the address of a quadword to save the old register value

On I64 systems, the initial state value and the scope of the modified state values differ depending on the location of the call to this routine, as shown in the following table.

Location of Call State Value Scope of New State Value

Mainline Determined by the compiler switches used when compiling the modules. Change is in effect until this service is called again, with the exception of ASTs (see below).

Condition handler The same as the state in effect when the condition occurs, unless the setting was changed by a previous condition handler. Change is in effect until all remaining condition handlers have been called or this service is called again.

AST routine Determined by the compiler switches used when compiling the modules, regardless of the state value in effect when the AST was triggered. Change is in effect only until the AST completes or this service is called again.

On Alpha systems, calling this routine changes the setting for ASTs as well as the mainline program.
Required Access or Privilege

None
Required Quota

None
Related Services

$IEEE_SET_PRECISION_MODE
$IEEE_SET_ROUNDING_MODE

Location of Call	State Value	Scope of New State Value
Mainline	Determined by the compiler switches used when compiling the modules.	Change is in effect until this service is called again, with the exception of ASTs (see below).
Condition handler	The same as the state in effect when the condition occurs, unless the setting was changed by a previous condition handler.	Change is in effect until all remaining condition handlers have been called or this service is called again.
AST routine	Determined by the compiler switches used when compiling the modules, regardless of the state value in effect when the AST was triggered.	Change is in effect only until the AST completes or this service is called again.

Condition Values Returned

SS$_NORMAL The service completed successfully.

SS$_ACCVIO The specified argument cannot be read or cannot be written.

$IEEE_SET_PRECISION_MODE (I64 Only)

On I64 systems, modifies the IEEE precision mode and, optionally, returns the previous value.

Format

SYS$IEEE_SET_PRECISION_MODE new_value , [*prev_value]

C Prototype

int sys$ieee_set_rounding_mode (int new_value, int *prev_value);

Arguments

new_value

OpenVMS usage: IEEE precision mode

type: longword (unsigned)

access: read only

mechanism: by value

The new value can be one of the following:

Symbol Value Meaning

IEEE$C_PM_NO_CHANGE -1 No change. Just get previous value

IEEE$C_PM_SINGLE 0 Single Precision

IEEE$C_PM_DOUBLE 2 Double Precision

IEEE$C_PM_DOUBLE_EXTENDED 3 Double-Extended Precision

prev_value

OpenVMS usage: IEEE precision mode

type: longword (unsigned)

access: write only

mechanism: by reference

The previous value is a pointer to a return value that can be one of the last three items from the table showing new values.

Symbol	Value	Meaning
IEEE$C_PM_NO_CHANGE	-1	No change. Just get previous value
IEEE$C_PM_SINGLE	0	Single Precision
IEEE$C_PM_DOUBLE	2	Double Precision
IEEE$C_PM_DOUBLE_EXTENDED	3	Double-Extended Precision

Description

The initial precision mode and the scope of the modified precision mode differ depending on the location of the call to this routine, as shown in the following table.

Location of Call Initial Precision Mode Scope of New Precision Mode

Mainline Determined by the compiler switches used when compiling the modules. Change is in effect until this service is called again with the exception of ASTs (see below).

Condition handler The same as the precision mode in effect when the condition occurs, unless the setting was changed by a previous condition handler. Change is in effect until all remaining condition handlers have been called or this service is called again.

AST routine Determined by the compiler switches used when compiling the modules, regardless of the precision in effect when the AST was triggered. Change is in effect only until the AST completes or this service is called again.

Required Access or Privileges

None
Required Quotas

None
Related Services

$IEEE_SET_FP_CONTROL
$IEEE_SET_ROUNDING_MODE

Location of Call	Initial Precision Mode	Scope of New Precision Mode
Mainline	Determined by the compiler switches used when compiling the modules.	Change is in effect until this service is called again with the exception of ASTs (see below).
Condition handler	The same as the precision mode in effect when the condition occurs, unless the setting was changed by a previous condition handler.	Change is in effect until all remaining condition handlers have been called or this service is called again.
AST routine	Determined by the compiler switches used when compiling the modules, regardless of the precision in effect when the AST was triggered.	Change is in effect only until the AST completes or this service is called again.

$IEEE_SET_ROUNDING_MODE (I64 Only)

On I64 systems, modifies the IEEE rounding mode and, optionally, returns the previous value.

Format

SYS$IEEE_SET_ROUNDING_MODE new_value , [*prev_value]

C Prototype

int sys$ieee_set_rounding_mode (int new_value, int *prev_value);
,

Arguments

new_value

OpenVMS usage: IEEE rounding mode

type: longword (unsigned)

access: read only

mechanism: by value

The new value can be one of the following:

Symbol Value Meaning

IEEE$C_RM_NO_CHANGE -1 No change. Just get previous value

IEEE$C_RM_NEAREST 0 Nearest (or even)

IEEE$C_RM_DOWN 1 -Infinity (down)

IEEE$C_RM_UP 2 +Infinity (up)

IEEE$C_RM_TRUNCATE 3 Zero (truncate/chop)

prev_value

OpenVMS usage: IEEE rounding mode

type: longword (unsigned)

access: write only

mechanism: by reference

The previous value is a pointer to a return value that can be one of the last four items from the table showing new values.

Symbol	Value	Meaning
IEEE$C_RM_NO_CHANGE	-1	No change. Just get previous value
IEEE$C_RM_NEAREST	0	Nearest (or even)
IEEE$C_RM_DOWN	1	-Infinity (down)
IEEE$C_RM_UP	2	+Infinity (up)
IEEE$C_RM_TRUNCATE	3	Zero (truncate/chop)

Description

The initial rounding mode and the scope of the modified rounding mode differ depending on the location of the call to this routine, as shown in the following table.

Location of Call Initial Rounding Mode Scope of New Rounding Mode

Mainline Determined by the compiler switches used when compiling the modules. Change is in effect until this service is called again, with the exception of ASTs (see below).

Condition handler The same as the rounding mode in effect when the condition occurs, unless the setting was changed by a previous condition handler. Change is in effect until all remaining condition handlers have been called or this service is called again.

AST routine Determined by the compiler switches used when compiling the modules, regardless of the rounding in effect when the AST was triggered. Change is in effect only until the AST completes or this service is called again.

Required Access or Privileges

None
Required Quota

None
Related Services

$IEEE_SET_FP_CONTROL
$IEEE_SET_PRECISION_MODE

Location of Call	Initial Rounding Mode	Scope of New Rounding Mode
Mainline	Determined by the compiler switches used when compiling the modules.	Change is in effect until this service is called again, with the exception of ASTs (see below).
Condition handler	The same as the rounding mode in effect when the condition occurs, unless the setting was changed by a previous condition handler.	Change is in effect until all remaining condition handlers have been called or this service is called again.
AST routine	Determined by the compiler switches used when compiling the modules, regardless of the rounding in effect when the AST was triggered.	Change is in effect only until the AST completes or this service is called again.

$INIT_SYS_ALIGN_FAULT_REPORT (Alpha and I64)

On Alpha and I64 systems, initializes system process alignment fault reporting.
This service accepts 64-bit addresses.

Format

SYS$INIT_SYS_ALIGN_FAULT_REPORT match_table ,buffer_size ,flags

C Prototype

int sys$init_sys_align_fault_report (void *match_table, int buffer_size, unsigned int flags);

Arguments

match_table

OpenVMS usage: address

type: longword (unsigned)

access: read

mechanism: by 32-bit or 64-bit reference

Describes the system fault match table. The match_table argument is the 32-bit or 64-bit virtual address of an array of longwords describing the system fault match table. The first longword is the number of match entries; the remaining longwords are the match entries.
The match table is used to restrict the number of alignment faults reported. Each entry in the table is a bit mask divided into three groups: mode bits, program counter (PC) space bits, and virtual address (VA) space bits.
The following table lists the symbols that can be used to define these bits:

Bit Type Symbols

Mode bits AME$M_KERNEL_MODE Kernel mode

AME$M_EXEC_MODE Executive mode

AME$M_SUPER_MODE Supervisor mode

AME$M_USER_MODE User mode

Program counter bits AME$M_USER_PC PC in User space

AME$M_SYSTEM_PC PC in System space

Virtual address bits AME$M_SYSTEM_VA VA in System space

AME$M_USER_VA_P0 VA in User P0 space

AME$M_USER_VA_P1 VA in User P1 space

AME$M_USER_VA_P2 VA in User P2 space

The following diagram illustrates the data structure of the match table:

Bit Type	Symbols
Mode bits	AME$M_KERNEL_MODE	Kernel mode
	AME$M_EXEC_MODE	Executive mode
	AME$M_SUPER_MODE	Supervisor mode
	AME$M_USER_MODE	User mode
Program counter bits	AME$M_USER_PC	PC in User space
	AME$M_SYSTEM_PC	PC in System space
Virtual address bits	AME$M_SYSTEM_VA	VA in System space
	AME$M_USER_VA_P0	VA in User P0 space
	AME$M_USER_VA_P1	VA in User P1 space
	AME$M_USER_VA_P2	VA in User P2 space

When an alignment fault occurs, a fault bit mask is created with one bit set in each group. The alignment fault handler then compares this fault bit mask against each entry in the match table. If the fault bit mask is a subset of an entry in the match table, the fault is reported.

buffer_size

OpenVMS usage:	byte count
type:	longword (signed)
access:	read
mechanism:	by value

The number of bytes to allocate, from nonpaged pool, to save the alignment fault data. The buffer you allocate must be sufficient to accommodate one data item of the size specified in the flags argument.

flags

OpenVMS usage:	mask_longword
type:	longword (unsigned)
access:	read only
mechanism:	by value

Flag bit mask specifying options for the $GET_SYS_ALIGN_FAULT_DATA operation.

If the flags argument is 0, data items of size AFR$K_VMS_LENGTH will be returned. If the flags argument is AFR$M_USER_INFO, the user name and image name are added to each data item and they are returned in a buffer of length AFR$K_EXTENDED_LENGTH. If the user name and image name are not available, an empty string is returned in the data item.

Description

The Initialize System Alignment Fault Reporting service initializes system alignment fault reporting.
System alignment faults must be written to a buffer. The following diagram illustrates the format in which system alignment fault data is saved in the buffer:

Only one user on a system can initialize system alignment fault reporting at any time. Subsequent calls will return SS$_AFR_ENABLED.

System alignment fault reporting is disabled when the program that called the service completes.

Required Access or Privileges

CMKRNL privilege is required.

Required Quota

None

Related Services

$GET_ALIGN_FAULT_DATA, $GET_SYS_ALIGN_FAULT_DATA, $PERM_DIS_ALIGN_FAULT_REPORT, $PERM_REPORT_ALIGN_FAULT, $START_ALIGN_FAULT_REPORT, $STOP_ALIGN_FAULT_REPORT, $STOP_SYS_ALIGN_FAULT_REPORT

Condition Values Returned

SS$_NORMAL The service completed successfully.

SS$_ACCVIO The match table is not read accessible.

SS$_AFR_ENABLED The service was already called.

SS$_BADPARAM The buffer_size argument is less than the minimum size required. If the flags argument is 0, AFR$K_VMS_LENGTH + 32 is required. If the flags argument is 1, AFR$K_EXTENDED_LENGTH + 32 is required.

SS$_NOPRIV The caller does not have CMKRNL privilege.

$INIT_VOL

Formats a disk or magnetic tape volume and writes a label on the volume. At the end of initialization, the disk is empty except for the system files containing the structure information. All former contents of the volume are lost.

Format

SYS$INIT_VOL devnam, volnam [,itmlst]

C Prototype

int sys$init_vol (void *devnam, void *volnam, void *itmlst);

Arguments

devnam

OpenVMS usage: char_string

type: character string

access: read only

mechanism: by descriptor

Name of the device on which the volume is physically mounted. The descriptor must point to the device name, a character string of 1 to 64 characters. The device name can be a physical device name or a logical name; if it is a logical name, it must translate to a physical name.
The device does not have to be currently allocated; however, allocating the device before initializing it is recommended.
volnam

OpenVMS usage: char_string

type: character string

access: read only

mechanism: by descriptor

Identification to be encoded on the volume. The descriptor must point to the volume name, a character string of 1 to 12 characters. For a disk volume name, you can specify a maximum of 12 ANSI characters; for a magnetic tape volume name, you can specify a maximum of 6 ANSI "a" characters.
Any valid ANSI "a" characters can be used; these include numbers, uppercase letters, and any one of the following nonalphanumeric characters:
! " % ' ( ) * + , - . / : ; < = >
HP strongly recommends that a disk volume name consist of only alphanumeric characters, dollar signs ($), underscores (_), and hyphens (-).
itmlst

OpenVMS usage: item_list_3

type: longword (unsigned)

access: read only

mechanism: by reference

Item list specifying options that can be used when initializing the volume. The itmlst argument is the address of a list of item descriptors, each of which describes one option. The list of item descriptors is terminated by a longword of 0.
The following diagram depicts the format of a single item descriptor:

The following table defines the item descriptor fields:

Descriptor Field Definition

Buffer length A word specifying the length (in bytes) of the buffer that supplies the information $INIT_VOL needs to process the specific item code. The length of the buffer needed depends on the item code specified in the item descriptor.

Item code A word containing an option for the initialize operation. These codes are defined by the $INITDEF macro. There are three types of item codes:

Boolean item code Boolean item codes specify a true or false value. The form INIT$_ code specifies a true value and the form INIT$_NO_ code specifies a false value. For Boolean item codes, the buffer length and buffer address fields of the item descriptor must be 0.

Symbolic value item code Symbolic value item codes specify one of a specified range of possible choices. The buffer length and buffer address fields of the item descriptor must be 0.

Input value item code Input value item codes specify a value to be used by $INIT_VOL. The buffer length and buffer address fields of the item descriptor must be nonzero.

Buffer address A longword containing the address of the buffer that supplies information to $INIT_VOL.

Return length address This field is not used.

Item Codes

INIT$_ACCESSED
An input item code that specifies the number of directories allowed in system space on the volume.
You must specify an integer between 0 and 255 in the input buffer. The default value is 3.
The INIT$_ACCESSED item code applies only to Files-11 On-Disk Structure Level 1 disks.
INIT$_BADBLOCKS_LBN
An input item code that enables $INIT_VOL to mark bad blocks on the volume; no data is written to those faulty areas. INIT$_BADBLOCKS_LBN specifies faulty areas on the volume by logical block number and block count.
The buffer from which $INIT_VOL reads the option information contains an array of quadwords containing information in the following format:

The following table describes the information to be specified for INIT$_BADBLOCKS_LBN:

Field Symbol Name Description

Logical block number INIT$L_BADBLOCKS_LBN Specifies the logical block number of the first block to be marked as allocated.

Count INIT$L_BADBLOCKS_COUNT Specifies the number of blocks to be allocated. This range begins with the first block, as specified in INIT$L_BADBLOCKS_LBN.

Field	Symbol Name	Description
Logical block number	INIT$L_BADBLOCKS_LBN	Specifies the logical block number of the first block to be marked as allocated.
Count	INIT$L_BADBLOCKS_COUNT	Specifies the number of blocks to be allocated. This range begins with the first block, as specified in INIT$L_BADBLOCKS_LBN.

Contents

Index

OpenVMS usage:	mask_quadword
type:	quadword (unsigned)
access:	read only
mechanism:	by reference

SS$_NORMAL	The service completed successfully.
SS$_ACCVIO	The specified argument cannot be read or cannot be written.

OpenVMS usage:	IEEE precision mode
type:	longword (unsigned)
access:	read only
mechanism:	by value

OpenVMS usage:	IEEE rounding mode
type:	longword (unsigned)
access:	read only
mechanism:	by value

OpenVMS usage:	address
type:	longword (unsigned)
access:	read
mechanism:	by 32-bit or 64-bit reference

OpenVMS usage:	char_string
type:	character string
access:	read only
mechanism:	by descriptor

OpenVMS usage:	item_list_3
type:	longword (unsigned)
access:	read only
mechanism:	by reference