Displaying the IAR Linker summary

Introduction

By default, CMake will suppress the output provided by the underlying build tools, though sometimes it is convenient to get some output at build-time such as the binary's resource consumption provided by the IAR ILINK linker's summary. In this article, we will explore one way of overriding CMake's default behavior.

Helpful Resources

• option()
• if()
• string()
• CMAKE_EXE_LINKER_FLAGS
• cmake -D

Description

Starting from CMake 3.27, the IAR linker's --silent flag is not hardcoded. A CMake option() can be used to choose when to display the linker-provided information.

For example:

cd tutorial
mkdir build
cd build
cmake .. -G Ninja --toolchain ../bxarm.cmake

And then:

cmake --build .

It will give an output similar to:

[2/2] Linking C executable tutorial.elf

Customizing your toolchain file

To display the summary by default, append the following snippet to your toolchain file:

option(ISPLAY_LINKER_SUMMARY "Display linker resource usage" ON)
if(ISPLAY_LINKER_SUMMARY)
  string(REGEX REPLACE "(^| )(--silent|-S)($| )" " " CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS}")
endif()

And then, build again:

cmake --build .

CMake will regenerate the build system and, by default, give an output similar to:

[0/1] Re-running CMake...
-- Configuring done (0.0s)
-- Generating done (0.0s)
-- Build files have been written to: /path/to/cmake-tutorial/tutorial/build
[1/1] Linking C executable tutorial.elf

  IAR ELF Linker V9.40.1.364/LNX for ARM
  Copyright 2007-2023 IAR Systems AB.

    972 bytes of readonly  code memory
     48 bytes of readonly  data memory
 16'392 bytes of readwrite data memory

Errors: none
Warnings: none

Link time:   0.00 (CPU)   0.00 (elapsed)

Hiding the linker summary

To temporarily disable the -DISPLAY_LINKER_SUMMARY option, use:

cmake .. -DISPLAY_LINKER_SUMMARY=OFF

-- Configuring done (0.0s)
-- Generating done (0.0s)
-- Build files have been written to: /path/to/cmake-tutorial/tutorial/build

And rebuild the project:

cmake --build .

The linker output should be again suppressed as in the default CMake behavior.