Dummyio.Hidden IO var allocated by the ISaGRAF linker

Product : ISaGRAF V3

Date : 5-March-1996

File : Dummyio.Hidden IO var allocated by the ISaGRAF linker.htm

Subject : Hidden I/O variables allocated by the ISaGRAF linker

Keywords: unused variables - Appli.tst - symbol table

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ISaGRAF V3.3x systematically includes in the application code (and

also in the symbol table) all the variables declared in the

application, even if not referenced in the programs. This has been

done to ease on-line modification: variables can be reserved for

future extensions in the application.

Undeclared variables are created by ISaGRAF compiler for each

unwired I/O channel.

Having an empty I/O channel consumes one variable, exactly as if a

declared variable was connected.

The variable can be understood as the "%..." available in IEC languages

for the I/O channel.

There is no information, after compiling, which can allow the

filtering of the symbols stored in TST file, whether a variable is

used or not.

This concerns variables really declared by the programmer. All other

variables allocated by the compiler (name beginning with an

underscore) do not appear in the symbol table.

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