▁where ▁the ▁initial ▁problem ▁happened . ▁In ▁those ▁cases , ▁memory ▁debugger ▁tools ▁may ▁be ▁needed . ▁ ▁In ▁certain ▁situations , ▁general ▁purpose ▁software ▁tools ▁that ▁are ▁language ▁specific ▁in ▁nature ▁can ▁be ▁very ▁useful . ▁These ▁take ▁the ▁form ▁of ▁static ▁code ▁analysis ▁tools . ▁These ▁tools ▁look ▁for ▁a ▁very ▁specific ▁set ▁of ▁known ▁problems , ▁some ▁common ▁and ▁some ▁rare , ▁within ▁the ▁source ▁code , ▁concentr ating ▁more ▁on ▁the ▁semantics ▁( e . g . ▁data ▁flow ) ▁rather ▁than ▁the ▁syntax , ▁as ▁comp ilers ▁and ▁interpre ters ▁do . ▁ ▁Both ▁commercial ▁and ▁free ▁tools ▁exist ▁for ▁various ▁languages ; ▁some ▁claim ▁to ▁be ▁able ▁to ▁detect ▁hundreds ▁of ▁different ▁problems . ▁These ▁tools ▁can ▁be ▁extremely ▁useful ▁when ▁checking ▁very ▁large ▁source ▁trees , ▁where ▁it ▁is ▁imp ract ical ▁to ▁do ▁code ▁walk - through s . ▁A ▁typical ▁example ▁of ▁a ▁problem ▁detected ▁would ▁be ▁a ▁variable ▁dere ference ▁that ▁occurs ▁before ▁the ▁variable ▁is ▁assigned ▁a ▁value . ▁As ▁another ▁example , ▁some ▁such ▁tools ▁perform ▁strong ▁type ▁checking ▁when ▁the ▁language ▁does ▁not ▁require ▁it . ▁Thus , ▁they ▁are ▁better ▁at ▁loc ating ▁likely ▁errors ▁in ▁code ▁that ▁is ▁s ynt act ically ▁correct . ▁But ▁these ▁tools ▁have ▁a ▁reputation ▁of ▁false ▁posit ives , ▁where ▁correct ▁code ▁is ▁flag ged ▁as ▁dub ious . ▁The ▁old ▁Unix ▁l int ▁program ▁is ▁an ▁early ▁example . ▁ ▁For ▁debugging ▁electronic ▁hardware ▁( e . g ., ▁computer ▁hardware