Could non-executable heap be a compile time error? (IDFGH-14014)

[projectgus]

Is your feature request related to a problem?

(This feature request relates to bug reports #14835 and #14836)

Most default ESP-IDF configurations no longer support executable heap:

• ESP_SYSTEM_MEMPROT_FEATURE is enabled by default on supported ESP32-S2,S3, probably others.
• ESP_SYSTEM_PMP_IDRAM_SPLIT is enabled by default on ESP32-C6, maybe others.

In both cases heap_caps_malloc(n, MALLOC_CAP_EXEC) is not expected to succeed.

This is fine and good, Writable XOR Executable memory access is a very sensible default for security.

Describe the solution you'd like.

From my perspective as a programmer trying to get executable memory[^], it'd be nice to get this failure at compile time instead of runtime, i.e. If config does not allow executable heap then don't define the MALLOC_CAP_EXEC flag.

[^] For MicroPython native code modules.

Describe alternatives you've considered.

Alternative is the current behaviour: get back a NULL pointer at runtime (unless there's a bug), and then realise you need to change the config yourself.

Additional context.

I guess this is probably a breaking API change, so maybe one for IDF 6?

[SoucheSouche]

Hi @projectgus, I created an MR to make MALLOC_CAP_EXEC definition conditional.
It was reviewed, but since it represents a breaking change, it will be most likely merged for 6.0 release.