AN3350 datasheet(79/185 Pages) STMICROELECTRONICS

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AN3350

Working with the ELF linker

Doc ID 018512 Rev 2

79/185

Closure blocks allow you to prevent the linker from dead stripping specified symbols. The

closure is transitive — all symbols referenced by the closed symbol are also forced into

closure.

There are two types of closure blocks:

●

Symbol-level closure blocks

●

Section-level closure blocks

Symbol-level closure blocks

Use FORCE_ACTIVE when you want to include a symbol in the link that would not be

otherwise included. For example:

FORCE_ACTIVE {break_handler, interrupt_handler, my_function}

Section-level closure blocks

Use KEEP_SECTION when you want to keep a section (usually a user-defined section) in

the link. For example:

KEEP_SECTION {.interrupt1, .interrupt2}

A variant is REF_INCLUDE. It keeps a section in the link, but only if the file from which the

section comes is referenced. This is very useful for including version numbers. For example:

REF_INCLUDE {.version}

11.3

Linker command file syntax

This section describes some practical ways in which you can use the commands of the

linker command file to perform common tasks.

The topics in this section are:

●

Alignment

●

Arithmetic operations

●

Comments

●

Dead strip prevention

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Expressions, variables and integral types

●

File selection

●

Writing data to memory

11.3.1

Alignment

Use the ALIGN command to align data on a specific byte-boundary. For example, the

following fragment uses ALIGN to increment the location counter to the next 16-byte

boundary. Example 14 shows an example of using the ALIGN command.

Example 14 Example ALIGN command

file.o (.text)

ALIGN (0x10);

file.o (.data) // this is aligned on a 16-byte boundary

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