Clarification on Dynamic Memory Allocation Usage and Extension in MCUboot

[PragatiGarg-eaton]

While working with loader.c, I noticed that dynamic memory allocation functions like malloc are used in the file, but I couldn’t find their definitions within the repository itself (except in run.c).

I’d like to understand:

• Where are these allocation functions expected to be defined or linked from?
• Are they provided by the platform, toolchain, or a specific configuration?
• What is the recommended way to use dynamic memory allocation in other parts of MCUboot or in custom extensions?
• Is there a preferred way to override or customize memory allocation behavior for platforms that don’t support standard malloc?

Any insights or references would be greatly appreciated to help ensure proper integration and alignment with MCUboot’s design principles.

Thanks in advance!

cc: @de-nordic @nordicjm @d3zd3z

[nordicjm]

malloc in that file is used for split image mode which is used by mynewt only, if you use that then it is expected your OS or build system provides though functions and you can use a define to change it to another function e.g. as is in boot/zephyr/include/os/os_malloc.h