Missing `.debug_info` Section in DWARF Information

[hapeeeeee]

I attempted to use the gimli library to parse a WebAssembly (Wasm) file that includes debug information. The Wasm file was written in Motoko and compiled using moc. However, my program reported that the .debug_info section was missing.

To investigate further, I used wasm-objdump to inspect the sections within the Wasm file. As expected, the .debug_info section was indeed absent.

[crusso]

Did you use the moc -g flag? We do produce some dwarf debug info, but gave up pursuing this further. @ggreif would know more about the status and which version of Dwarf we were emitting.

[hapeeeeee]

Did you use the flag? We do produce some dwarf debug info, but gave up pursuing this further. @ggreif would know more about the status and which version of Dwarf we were emitting.moc -g

Sure. I used the -g option with moc, and as shown in the screenshot, the DWARF information already includes custom sections like debug_line and debug_line_str. These were generated through the -g option. However, the most essential section, debug_info, is still missing.

[ggreif]

RIght, we never finalised the DWARF5 generation as we had more important stuff to do. There is no way to attach a debugger to the IC or a local replica for that matter. The only way to attach a debugger was via WASI compilation and bare wasmtime. So the best one could use it for was to debug modules running in that context. The value in that didn't justify the effort necessary at that time.

The PR for the third part of DWARF is still around, but seriously bitrotten and was woefully incomplete. It was a tech demo at most.

[hapeeeeee]

Alright, in fact, I have already parsed the debug_line and debug_line_str sections in a secondary way to obtain line number information for the Motoko debugger. However, just like in #4939, the parsed line number information is incorrect, which is critical — incorrect line numbers make it completely impossible to support the development of the Motoko debugger.