Feature Request: Add small stack mode for wolfCOSE

[aidangarske]

Feature Plan: wolfCOSE "Small Stack" Mode

The Problem: "Stack Exhaustion"

In many embedded environments (STM32, ESP32, or custom RTOS tasks), the stack is a precious, fixed resource. wolfCOSE, in its current "no-malloc" state, forces all buffers and structures onto the stack. For complex COSE objects (signatures + certs + payload), this can exceed the available stack depth, leading to hard faults.

Proposed Naming Options

Since we want this to sound functional but "cool," here are a few directions for the --enable flag and the macro:

• --enable-small-stack (Simple, clear, user-centric)
• --enable-heap-buffers (Technical, explicit about memory location)
• --enable-low-stack-footprint (Professional)
• WOLFCOSE_LOW_STACK (The internal macro)

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Updated Phase 1: Logic & Naming

We will wrap the dynamic allocation logic specifically under a "Small Stack" umbrella.

• Macro Logic:

  /* If the user wants to save stack, we default to heap usage */
  #if defined(WOLFCOSE_SMALL_STACK) || defined(WOLFCOSE_DYNAMIC_ALLOCATION)
      #define WC_COSE_USE_HEAP
  #endif

Updated Phase 4: Stack Auditing

Since the goal is to accommodate small stacks, we don't just add malloc—we also need to find where the current code is "stack-heavy."

1. Identify Large Locals: Use the Fenrir Prompt (from our previous chat) to specifically target "Category B.4: Stack Minimization."
2. Heap-Promotion: Any local array larger than, say, 128 bytes should be conditionally moved to the heap when WC_COSE_USE_HEAP is defined.
3. The "Safety Valve": If WC_COSE_USE_HEAP is NOT defined and a function detects a payload larger than the static buffer, it must return a specific error code like BUFFER_TOO_SMALL_E rather than overflowing.