ld Manual

Introduction to ld

ld Manual—529650.001

1-23

ld Compilation Rules

ld enforces separate compilation rules for linking native programs in C, C++, COBOL,

and pTAL.

Case-Sensitivity

C and C++ are case-sensitive; COBOL and pTAL are not. In C and C++, the symbol

names x and X refer to different symbols. In COBOL and pTAL, all symbol names are

converted to uppercase letters, so x and X refer to the same symbol.

Local and Shared Symbols

A local symbol is known only within a single compilation unit. A shared symbol is

known by all compilation units that are linked together.

A local symbol is distinct from any other symbol of the same name that appears in

other compilation units. Because a shared symbol is known by all compilation units that

are linked together, all compilation units refer to the same symbol at run time.

The pTAL compiler has various rules for grouping data items into blocks. You can

declare separate data items in pTAL, outside any explicit data blocks, and have them

remain individual data items across separate compilation units. (This behavior is

identical to that in C and C++.) The pTAL compiler can also group data items together

into a single data block named _GLOBAL. The pTAL compiler can also put the prefix “$”

on the name of a data block. See the pTAL Reference Manual for details on declaring

and sharing data blocks in pTAL.

Table 1-4. Local and Shared Symbols by Language

Language Local Symbols: Names of ... Shared Symbols: Names of ...

C++

Static data items

Static functions

Data items declared outside functions

All other functions

COBOL Data records (level 01 data items) that

are not declared external

Subordinate data items (levels 02-nn)

Programs nested within other

programs

External data items

External file connectors

pTAL Private data blocks whose NAME

declarations are unique

Subprocedures

Names of data block members*

All other data blocks

* For example, if a data block is named B and it contains an integer named I, B is the only name that ld

considers for separate compilation rules. It is possible that B will be confused with a data item named B in C

compilation units.