[all-commits] [llvm/llvm-project] 22357f: [analyzer] Avoid unnecessary super region invalida...

[flovent via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 22357fe33a8a8cc221632e32cb443676f1feeda9
      https://github.com/llvm/llvm-project/commit/22357fe33a8a8cc221632e32cb443676f1feeda9
  Author: flovent <flbven at protonmail.com>
  Date:   2025-07-07 (Mon, 07 Jul 2025)

  Changed paths:
    M clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp
    A clang/test/Analysis/cstring-should-not-invalidate.cpp

  Log Message:
  -----------
  [analyzer] Avoid unnecessary super region invalidation in `CStringChecker` (#146212)

Bounded string functions takes smallest of two values as it's copy size
(`amountCopied` variable in `evalStrcpyCommon`), and it's used to
decided whether this operation will cause out-of-bound access and
invalidate it's super region if it does.

for `strlcat`: `amountCopied = min (size - dstLen - 1 , srcLen)`
for others: `amountCopied = min (srcLen, size)`

Currently when one of two values is unknown or `SValBuilder` can't
decide which one is smaller, `amountCopied` will remain `UnknownVal`,
which will invalidate copy destination's super region unconditionally.

This patch add check to see if one of these two values is definitely
in-bound, if so `amountCopied` has to be in-bound too, because it‘s less
than or equal to them, we can avoid the invalidation of super region and
some related false positives in this situation.

Note: This patch uses `size` as an approximation of `size - dstLen - 1`
in `strlcat` case because currently analyzer doesn't handle complex
expressions like this very well.

Closes #143807.



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