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These module docs are in beta and may be incomplete.

modm:build:scons: SCons Build Script Generator

SCons is a software construction build system written in Python. For a better embedded experience, we've extended it with a custom build tools by the DLR as well as our own modm-specific build tools.

This module generates two files:

  • a modm/SConscript file: configures all required SCons tools with the right settings (also using information from the modm:build module) to compile the modm library.
  • a top-level SConstruct file: configures additional, optional tools and sets up all the relevant SCons functions for your target.

The SConscript file is self contained and does not depend on anything outside of the modm/ directory. This allows it to be combined with SConscript of other projects without clashing.

In fact, if you look at your generated SConstruct file, you'll notice that it doesn't contain a lot of logic or specific data, it is only meant for calling the right SCons tool with the right arguments.

We do not intend to serve every possible use-case with this module. If you need something special, write your own SConstruct file, maybe starting by modifying ours. Remember to set modm:build:scons:include_sconstruct to False, so that your custom SConstruct does not get overwritten.

SCons Methods

This module generates these SCons methods depending on the target.


Defaults to scons build.

You can add these arguments to any of the scons commands:

  • verbose=1: gives a more verbose output, so you can, for example, check what options the compiler is called with.
  • profile=release: Compile project with the release profile options (default).
  • profile=debug: Compile project with the debug profile options.

For a description of the release and debug profiles, see the modm:build module documentation.

Debug Profile

When working with the debug profile, make sure to add profile=debug to all commands, especially scons program profile=debug and scons gdb profile=debug!

scons build

Compiles your application into an executable.

Example for a STM32 target:

 $ scons build
Compiling C++·· build/release/main.o
Compiling C···· build/release/modm/ext/tlsf/tlsf.o
Compiling C++·· build/release/modm/src/modm/ui/display/virtual_graphic_display.o
Compiling C++·· build/release/modm/src/modm/utils/dummy.o
Create Library· build/release/modm/libmodm.a
Indexing······· build/release/modm/libmodm.a
Linking········ build/release/game_of_life.elf

scons size

Displays the static Flash and RAM consumption of your target. (* only STM32 targets)

Example for a STM32 target with 16MB external heap:

 $ scons size
Memory usage:.. build/release/game_of_life.elf

Program:  12.8 KiB (0.6% used)
(.data + .fastcode + .fastdata + .hardware_init + .reset + .rodata +
 .table.copy.extern + .table.copy.intern + .table.section_heap + + .text)

Data:      5.8 KiB (1.5% used) = 2936 B static (0.7%) + 3040 B stack (0.8%)
(.bss + .data + .fastdata + .stack)

Heap:     16.4 MiB
(.heap0 + .heap1 + .heap2 + .heap3 + .heap5 + .heap_extern)

scons program

Writes the executable onto your target via Avrdude or OpenOCD. This is a convenience wrapper around the programming options and methods defined in the modm:build module. (* only AVR and STM32 targets)

Example for a STM32 target:

 $ scons program
.----OpenOCD--- build/release/game_of_life.elf
'-------------> stm32f469nih
Open On-Chip Debugger 0.10.0
Info : using stlink api v2
Info : Target voltage: 3.259396
Info : stm32f4x.cpu: hardware has 6 breakpoints, 4 watchpoints
** Programming Started **
auto erase enabled
Info : device id = 0x10006434
Info : flash size = 2048kbytes
Info : Dual Bank 2048 kiB STM32F42x/43x/469/479 found
wrote 16384 bytes from file build/release/game_of_life.elf in 0.589736s (27.131 KiB/s)
** Programming Finished **
** Verify Started **
verified 13064 bytes in 0.296308s (43.056 KiB/s)
** Verified OK **
shutdown command invoked

scons run

Executes your project on your computer. (* only Hosted targets)

scons gdb

Launches OpenOCD in the background, then launches GDB in foreground with the correct executable. When GDB exits, it stops the OpenOCD process. (* only STM32 targets)

This is just a convenience wrapper for the debug functionality defined in the modm:build module.

Choose the correct profile

When debugging, make sure to select the correct compilation profile. The firmware and the executable given to GDB have to be the some or you'll see GDB translate the program counter to the wrong code locations. When you suspect a bug in your firmware, consider that it was most likely compiled with the release profile, since that's the default. First try to scons gdb profile=release, and if that doesn't help, compile and scons program profile=debug and try scons gdb profile=debug again.

scons symbols

Dumps the symbol table for your executable.

 $ scons symbols
Show symbols for 'build/release/game_of_life.elf':
536871656 00000001 b (anonymous namespace)::nextOperation
536871657 00000001 b (anonymous namespace)::checkNextOperation
536871658 00000001 b (anonymous namespace)::error
536871444 00000001 b read_touch()::initialized
134228236 00000668 T I2C1_EV_IRQHandler
134224924 00001136 T otm8009a_init(unsigned char)
134221192 00001378 t _GLOBAL__sub_I_p
536871782 00002054 b (anonymous namespace)::txBuffer

scons listing

Decompiles your executable into an annotated assembly listing. This is very useful for checking and learning how the compiler translates C++ into assembly instructions:

 $ scons listing
Ext. Listing··· build/release/game_of_life.lss
 $ less build/release/game_of_life.lss
Disassembly of section .text:
08000d74 <main>:

 8000d74:   b508        push    {r3, lr}
 8000d76:   f7ff fcc9   bl  800070c <_ZN5Board10initializeEv>
 8000d7a:   f000 fd91   bl  80018a0 <_ZN5Board17initializeDisplayEv>
 8000d7e:   f7ff fc55   bl  800062c <_ZN5Board21initializeTouchscreenEv>
 8000d82:   f7ff feff   bl  8000b84 <_Z12game_of_lifev>

scons bin

Creates a binary file of your executable.

 $ scons bin
Binary File···· build/release/game_of_life.bin

scons -c

Cleans the build artifacts.

 $ scons -c
Removed build/release/main.o
Removed build/release/modm/ext/tlsf/tlsf.o

Removed build/release/modm/src/modm/ui/display/virtual_graphic_display.o
Removed build/release/modm/src/modm/utils/dummy.o
Removed build/release/modm/libmodm.a
Removed build/release/game_of_life.elf
Removed build/release/game_of_life.lss

scons cmakewrapper

Generates a CMakeLists.txt file that wraps the scons commands so that the project can be imported into IDE with CMake support, like CLion.

Consider this an unstable feature

scons qtcreator

Generates several files so that the project can be imported into Qt Creator via the .creator file importer. Note, that no compiliation or debugging features are supported, this is only meant for using the IDE as an editor.

Consider this an unstable feature

XPCC Generator Tool

The modm:communication:xpcc:generator module contains the Python tools to translate the XPCC XML declarations into various language implementations. This module contains a SCons wrapper tool, that understands the XML dependencies and automatically updates the generated files when it becomes necessary.

The wrapper tool is automatically used when the generator module is detected, and its options are evaluated for the wrapper as follows:


The generated files are available as a top-level #include <identifiers.hpp>.

Information Tool

Our info SCons tool generates a set of header files containing preprocessor defines with the repository state.

A call to env.InfoGit(with_status={True, False}) will generate a <info_git.h> header file and add these two defines to the command line CPP options:

  • MODM_GIT_STATUS: defined only if called with with_state=True.

You can enable this by setting the modm:build:scons:info.git option.

A call to env.InfoBuild() will generate a <info_build.h> header file and add this define to the command line CPP options:


You can enable this by setting the option.

Only include in source files

Since this information may change often, you must only #include the generated header files in source files, not in header files. Otherwise you risk a complete rebuild of your project every time this information changes! If you need to use the information in a header file, expose it as a extern const char *info_git_{name}; and initialize it with the defines in a separate source file. Then only this source file needs to be rebuild and the project relinked, which is significantly faster:

// In header file
extern const char *info_git_sha;
// In source file
const char info_git_sha[] = MODM_GIT_SHA;

Respect developers privacy

This information is placed into the firmware in cleartext, so it will be trivial to extract from a memory dump. Consider this information public as soon as it is uploaded to your target. Make sure you only use the information you absolutely need!

Git Information

These are the values defines as strings in <info_git.h>:

  • MODM_GIT_SHA: commit hash: %H.
  • MODM_GIT_SHA_ABBR: short commit hash: %h.
  • MODM_GIT_SUBJECT: commit subject as text: %s.
  • MODM_GIT_AUTHOR: author name: %an.
  • MODM_GIT_AUTHOR_EMAIL: author email: %ae.
  • MODM_GIT_AUTHOR_DATE: authoring date: %ad.
  • MODM_GIT_AUTHOR_DATE_TIMESTAMP: authoring date as Unix timestamp: %at.
  • MODM_GIT_COMMITTER: committer name: %cn.
  • MODM_GIT_COMMITTER_EMAIL: committer email: %ce.
  • MODM_GIT_COMMITTER_DATE: committer date: %cd.
  • MODM_GIT_COMMITTER_DATE_TIMESTAMP: committer das as Unix timestamp: %ct.
  • MODM_GIT_CONFIG_USER_NAME: local user name:
  • MODM_GIT_CONFIG_USER_EMAIL: local user email:

If called with_status=True, this information is added as well:

  • MODM_GIT_MODIFIED: number of modified files: M.
  • MODM_GIT_ADDED: number of added files: A.
  • MODM_GIT_DELETED: number of deleted files: D.
  • MODM_GIT_RENAMED: number of renamed files: R.
  • MODM_GIT_COPIED: number of copied files: C.
  • MODM_GIT_UPDATED_NOT_MERGED: number of updated, but not merged files: U.
  • MODM_GIT_UNTRACKED: number of untracked files: ?.

This is the output of the example/linux/git project showing an unclean repository state with uncommitted changes. This can give you a few hints as to where a firmware came from and help you pinpoint the source of a bug or feature.

Info:    Local Git User:
Info:    Name:  Name Surname
Info:    Email:
Info:    Last Commit:
Info:    SHA:             1b5a9a642857182161a615039c92907e59881614
Info:    Abbreviated SHA: 1b5a9a642
Info:    Subject:         wip
Info:    Author:
Info:    Name:      Name Surname
Info:    Email:
Info:    Date:      Tue Jul 17 22:23:20 2018 +0200
Info:    Timestamp: 1531859000
Info:    Committer:
Info:    Name:      Name Surname
Info:    Email:
Info:    Date:      Tue Jul 17 22:23:20 2018 +0200
Info:    Timestamp: 1531859000
Info:    File Status:
Info:    Modified:  10
Info:    Added:     0
Info:    Deleted:   0
Info:    Renamed:   0
Info:    Copied:    0
Info:    Untracked: 6

Build Information

These are the values defines as strings in <info_build.h>:

  • MODM_BUILD_PROJECT_NAME: as defined in the option.
  • MODM_BUILD_MACHINE: machine information.
  • MODM_BUILD_USER: user information.
  • MODM_BUILD_OS: OS version string (best effort, may not be useful!).
  • MODM_BUILD_COMPILER: compiler information.

The output of the examples/linux/build_info running on macOS:

Info:    Project:  build_info
Info:    Machine:  name.local
Info:    User:     user
Info:    Os:       Mac 10.12.6 (x86_64)
Info:    Compiler: g++-8 (Homebrew GCC 8.1.0) 8.1.0

Bitmap Tool

If the modm:build:scons:image.source is defined as a path, it'll be searched for .pbm files to convert into C++ data files using the bitmap tool:

source, header = env.Bitmap(bpm_file)

See the GraphicsDisplay::drawImage() method in the modm:ui:display module for how to use these generated files. The directory is added to the include search paths, so the generated files can be accessed as #include <image.hpp>.



Generate a SConstruct file: True{ True, False }

This overwrites any top-level SConstruct file!


Path to directory containing .pbm files: { String }


Generate git repository state information: Disabled{ Disabled, Info, Info+Status }

  • Info: generates information about the last commit.
  • Info+Status: like Info plus git file status.

Generate build state information: False{ True, False }


modm:build:scons modm_build_scons modm: build: scons modm_build modm: build modm_build_scons->modm_build