B-Lang-org/bsc

bsc crash when bs method arg name annotation doesn't match method arity

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#420 opened on Oct 2, 2021

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 (4 comments) (0 reactions) (0 assignees)Haskell (1,108 stars) (178 forks)batch import
ICEerror-messagesgood first issue

Description

if the arg_names annotation in a classic interface declaration has fewer names than the method has arguments, bsc crashes without any useful information:

bsc -verilog BugMethodArgNamesArity.bs
Prelude.!!: index too large

BugMethodArgNamesArity.bs is:

package BugMethodArgNamesArity where

interface ArityBug =
    foo :: Bool -> Bool -> Action {-# arg_names = [bar] #-}

{-# verilog mkArityBug #-}
mkArityBug :: Module ArityBug
mkArityBug = module
    interface
        foo _ _ = _

this specific crash occurs when !! is used in the definition of i' inside iExpandMethodLam at IExpand.hs:1065, although at least the !! in the definition of m_origion_type below has the exact same problem.

iirc the IExpand state monad handles errors, so it should be possible to check in iExpandMethodLam and emit a more informative error with a reasonable position; failing that, a quick-hack ICE with a position would also work.

Contributor guide

Tech stack
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Domain
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Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
5
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Haskell programmingBluespec syntaxcompiler internals
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
20
Research direction
Investigate the crash in bsc when method arg name annotation arity mismatches method arity. The crash occurs at IExpand.hs:1065 where '!!' is used. The fix should be in iExpandMethodLam to check argument name count and emit a proper error with position. See also the similar issue at m origion type. Locate the function iExpandMethodLam in src/comp/IExpand.hs and implement a pre condition check.