The initial load segment of a program object can contain a binder-generated
text class that describes the other loadable classes in the program
object. This descriptive class is only present in program objects
stored as
COMPAT=PM3 or higher and when one
of the following is true:
- The module has more than one loadable text class.
- There is a loadable text class whose name does not begin with
B_.
If COMPAT is specified or defaulted to PM1 or PM2,
this descriptive class is suppressed with no error indication. Language
Environment-enabled programs that do not use a prelinker step require
the IEWBLIT control block.
The information can be accessed in one of the following two ways:
- An
API can be used to retrieve the text from a stored program object.
- The standard binder API or the fast data API can be used.
- The class name is B_LIT and the section name is IEWBLIT.
- An external reference can be used by a program within the object
to locate the text.
- Use
the symbol name IEWBLIT.
- It must be a weak reference. For example, a WXTRN in assembler
terminology. The binder cannot create the B_LIT class until after
all other external symbols have been resolved. A strong reference
would be flagged as an error before the class could be created.
For either of the above means of access, the calling program
will see the data as a structure defined for assembler programs in
the shipped IEWBLIT mapping macro. The field names in that macro match
those used in
Table 1.
The structure contains names, locations, and lengths of each class
in the program object. It also contains the following attribute information
about each class:
- RMODE
- Boundary alignment
- Initial, deferred, or no load
- Read-only status
The structure begins with a header that specifies the number of
class entries and the length of each:
Table 1. BLIT structure format| Field Name |
Field Type |
Offset |
Length |
Description |
|---|
| BLIT_EYE_CATCHER |
Char |
0 |
8 |
Constant 'IEWBLIT ' |
| BLIT_ LENGTH |
Binary |
8 |
4 |
Total structure length with entries |
| BLIT_VERSION |
Binary |
12 |
1 |
Structure version = 1 |
| * |
|
13 |
3 |
* reserved * |
| BLIT_HEADER_LENGTH |
Binary |
16 |
4 |
Length to CTABLE |
| BLIT_CENTRY_LENGTH |
Binary |
20 |
4 |
Length of one class entry |
| BLIT_CENTRY_COUNT |
Signed |
24 |
4 |
Number of entries in the BLIT_CTABLE |
| BLIT_DEFER_COUNT |
Binary |
28 |
4 |
Number of class entries |
| * |
|
32 |
8 |
* reserved * |
| BLIT_LOADER_TOKEN |
Char |
40 |
8 |
[For loader use] |
| BLIT_CIE_ADDR |
Pointer |
48 |
4 |
Address of Import/Export table or offset in
segment on DASD |
| BLIT_MOD_ATTR |
Bit |
52 |
4 |
Module attributes |
| BLIT_XPLINK |
Bit |
52.0 |
0.1 |
XPLINK linkage convention |
| |
Bit |
52.1 |
0.2 |
reserved |
| BLIT_LC_CLASSES |
Bit |
52.3 |
0.2 |
Indicates if there are loadable C classes- 00
- not known if there are loadable C_ classes in module
- 10
- no loadable C_ classes in module
- 11
- 11=loadable C_ classes in module
|
| * |
|
56 |
8 |
* reserved * |
| BLIT_CTABLE |
|
64 |
|
Start of class entries |
Each of the class entries has the following format:
Table 2. BLIT class entry
format| Field Name |
Field Type |
Offset |
Length |
Description |
|---|
| BLIT_CLASS_NAME |
Char |
0 |
16 |
Name of class, blank padded |
| BLIT_CLASS_LENGTH |
Binary |
16 |
4 |
Length of class when loaded |
| BLIT_CLASS_ADDR |
Pointer |
20 |
4 |
Address of initial load class or offset in segment
on DASD or zero for deferred load class |
| BLIT_RMODE |
Binary |
24 |
1 |
00=RMODE_UNSPEC
01=RMODE_24
03=RMODE_ANY
04=RMODE_64
|
| BLIT_ALIGN |
Binary |
25 |
1 |
Power® of
2 class alignment in storage; for example, 3=doubleword aligned (2**3
= 8) |
| BLIT_LOAD_ATTR |
Bit |
26 |
1 |
|
BLIT_RO
|
Bit |
26.0 |
0.1 |
Read only if on |
BLIT_NOLOAD
|
Bit |
26.1 |
0.1 |
Always off – load classes are not listed in
this table |
BLIT_DEFER
|
Bit |
26.2 |
0.1 |
Deferred load if on |
BLIT_LANG_ATTR
|
Bit |
27 |
1 |
|
BLIT_PADDING
|
Bit |
27.0 |
0.1 |
The class has 16-byte initial padding. |
| |
|
28 |
4 |
* reserved * |