UM0144 datasheet(45/92 Pages) STMICROELECTRONICS

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ST7 Assembler Linker

6 Librarian

UM0144

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Librarian

6.1

Overview

If you do a lot of work on similar boards especially those with the same processor, it makes a great deal of

sense to reuse lumps of code you've already written to do the same task in a different program. At the

simplest level, you could just copy the source code as a block of text into the new program. This works

fine, but has a subtle disadvantage: if you update the subroutine, you have to hunt around all the usages

of it, performing the update on each.

To get around this problem, many people have the source for common routines in one place, and link the

.OBJ

module with each program needing routine. Then you only need to update the source code once,

reassemble it to get a new .OBJ file, then link again all the users of the routine, who will now have the new

.OBJ

file.

While this scheme works well, it generates some problems of its own. For example, each routine needs its

own .OBJ file. By nature, these common routines tend to be small, so you end up giving dozens of extra

.OBJ

modules to the linker, and having the .OBJ modules scattered around your hard disk.

The base concept of a librarian is to combine all these small, useful .OBJ modules into one large .LIB

library file. You could then tell the linker about the library, and it would take care of sorting out which .OBJ

modules to pull into link. It would know which ones to pull by the fact that the main code being linked would

have undefined externals, for example, to call the missing library routines. The librarian simply takes each

undefined external in turn, and checks it against all the modules in the library. If any of the modules

declares a

PUBLIC

of the same name, it knows you need that .OBJ module and it includes it

automatically.

6.2

Invoking the librarian

The librarian is called LIB, and takes one command line argument that is the name of the library to

operate on. If not given, you'll be prompted for it.

LIB [library name]

.LIB

is added if the suffix is left off.

If the library you indicate doesn't exist, LIB asks you if it's a new library.

For example:

LIB LIB1

STMicroelectronics - Librarian - rel 1.00

Couldn't open Library file 'LIB1.LIB'

is it a new file? (y/n): y

If the answer is 'n', LIB aborts. If the library exists, LIB prints up a report on the library.

Library LIB1.LIB is 2K long.

16/1024 Public labels used in 2/128 modules.

Next you're faced with the main prompt:

LIB1.LIB: Operation (<ENTER> for help):

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