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Disassembly

mcu-debug integrates with VS Code's built-in disassembly view to show ARM assembly for your firmware, interleaved with source code.

Opening the Disassembly View​

While paused at a breakpoint:

  1. Right-click in the editor → Open Disassembly View
  2. Or from the Command Palette: Debug: Open Disassembly View

The view shows assembly instructions with source lines interleaved where debug information is available.

Stepping in Disassembly View​

When the Disassembly View is focused:

  • Step Over (F10): advances by one instruction, not one source line
  • Step Into (F11): follows a branch instruction into the called function
  • Step Out (Shift+F11): runs until the current function returns

This is useful for:

  • Inspecting compiler-generated code around a suspicious source line
  • Debugging interrupt handlers and startup code with no source
  • Verifying that optimization-related issues are in the assembly, not the source

ELF Parsing​

mcu-debug uses the da-helper binary for fast ELF file parsing to extract symbol addresses and associate them with disassembly ranges. This avoids asking GDB to disassemble large regions (which can be slow).

Limitations​

  • Thumb/Thumb-2 instructions are displayed with their decoded mnemonics
  • Inline assembly in C is shown with surrounding compiled code
  • If debug symbols are stripped or the optimization level is high, source-interleaving may be incomplete