ARM VERSION 1.2 - Manual (Page 344)

Directives Reference
7-62 Copyright © 2000, 2001 ARM Limited. All rights reserved. ARM DUI 0068B
7.7.11 GLOBAL
See EXPORT or GLOBAL on page 7-58.
7.7.12 IMPORT
The IMPORT directive provides the assembler with a name that is not defined in the
current assembly.
IMPORT is very similar to EXTERN , except that the name is imported whether or not it is
referred to in the current assembly (see EXTERN on page 7-60, and EXPORT or
GLOBAL on page 7-58).
Syntax
IMPORT symbol{[WEAK]}
where:
symbol is a symbol name defined in a separately assembled source file, object
file, or library. The symbol name is case-sensitive.
WEAK prevents the linker generating an error message if the symbol is not
defined elsewhere. It also prevents the linker searching libraries that are
not already included.
Usage
The name is resolved at link time to a symbol defined in a separate object file. The
symbol is treated as a program address. If
[WEAK] is not specified, the linker generates
an error if no corresponding symbol is found at link time.
If [WEAK] is specified and no corresponding symbol is found at link time:
• If the reference is the destination of a B or BL instruction, the value of the symbol
is taken as the address of the following instruction. This makes the B or BL
instruction effectively a NOP .
• Otherwise, the value of the symbol is taken as zero.
To avoid trying to access symbols that are not found at link time, use code like the
example in EXTERN on page 7-60.