Relocatable Object Module Format (OMF) Specification
Relocatable Object Module Format (OMF) Specification
Relocatable Object Module Format (OMF) Specification
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<strong>Relocatable</strong> <strong>Object</strong> <strong>Module</strong> <strong>Format</strong><br />
Allocation Type (Low-Order 4 bits):<br />
Bit<br />
Allocation<br />
00H Explicit Allocate in the segment specified in the ensuing Base Group, Base Segment,<br />
and Base Frame fields.<br />
01H Far Code Allocate as CODE16. The linker will create segments to contain all COMDATs<br />
of this type.<br />
02H Far Data Allocate as DATA16. The linker will create segments to contain all COMDATs<br />
of this type.<br />
03H Code32 Allocate as CODE32. The linker will create segments to contain all COMDATs<br />
of this type.<br />
04H Data32 Allocate as DATA32. The linker will create segments to contain all COMDATs<br />
of this type.<br />
05H - 0FH<br />
Reserved.<br />
Align Field<br />
These codes are based on the ones used by the SEGDEF record:<br />
0 Use value from SEGDEF<br />
1 Byte aligned<br />
2 Word aligned<br />
3 Paragraph (16 byte) aligned<br />
4 Page aligned. (The original Intel specification uses<br />
256-byte pages, the IBM <strong>OMF</strong> implementation uses<br />
4096-byte pages.)<br />
5 Double word (4 byte) aligned<br />
6 Not defined<br />
7 Not defined<br />
Enumerated Data Offset Field<br />
This field specifies an offset relative to the beginning location of the symbol specified in the Public Name Index<br />
field and defines the relative location of the first byte of the Data field. Successive data bytes in the Data field<br />
occupy higher locations of memory. This works very much like the Enumerated Data Offset field in an LEDATA<br />
record, but instead of an offset relative to a segment, this is relative to the beginning of the COMDAT symbol.<br />
Type Index Field<br />
The Type Index field is encoded in index format; it contains either debug information or an old-style TYPDEF<br />
index. If this index is 0, there is no associated type data. Old-style TYPDEF indexes are ignored by most linkers.<br />
Linkers do not perform type checking.<br />
Public Base Field<br />
This field is conditional and is identical to the public base fields (Base Group, Base Segment, and Base Frame)<br />
stored in the PUBDEF record. This field is present only if the Allocation Type field specifies Explicit allocation.<br />
62 <strong>OMF</strong> <strong>Specification</strong>, Version 1.1 Tool Interface Standards (TIS)
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