BugFix: Code Bug Finder

BugFix reads the code you paste, works out whether it is Python, JavaScript or C++, and tells you what is wrong with it.

Every finding comes with three things: the line it is on, a plain explanation of how it actually fails, and the corrected form. No jargon, no rule codes you have to look up.

WHAT IT FINDS

Python: mutable default arguments, bare except blocks, comparing to None with ==, using is against a literal, tabs mixed with spaces, asserts on a tuple that can never fail, unreachable code, methods missing self, exceptions silently discarded, placeholders in a string that is missing its f prefix, Python 2 print statements, and shadowed built-ins.

JavaScript: loose == comparisons, assignment where a comparison was meant, switch cases that fall through, parseInt without a radix, eval, innerHTML assignment, var captured by a closure inside a loop, await inside a function that is not async, the bare return that silently returns undefined, reassigning a const, unreachable code, and var where let or const belongs.

C++: unbounded strcpy, strcat, sprintf and gets, scanf %s with no field width, new without delete, malloc without free, delete used where delete[] was needed, assignment inside a condition, classes with virtual methods but no virtual destructor, switch fallthrough, returning the address of a local, comparing floating point with ==, loops that run one past the end, and using namespace std at file scope.

Unbalanced brackets are caught in all three languages.

BUILT TO STAY QUIET

A bug finder that cries wolf is worse than no bug finder. BugFix strips comments and string contents before it looks for anything, so a comparison written inside a message or a comment never triggers a warning. Rules are written narrowly and stay silent on idiomatic code.

COMPLETELY OFFLINE

BugFix requests no permissions and has no internet access at all. The code you paste is analysed on your device and never leaves it. There are no accounts, no ads, no analytics and no trackers.

Free, with everything included.

Recent changes:
First release.

Paste Python, JavaScript or C++ and BugFix works out the language and reports the bugs, each with its line number, an explanation of how it fails, and the corrected form.

36 checks across the three languages, plus bracket balancing. Everything runs on your device; the app has no permissions and no internet access.