[NFC] Fix potential underflow constant.

[zahiraam]

If the range for llvm::any_of is empty, Idx will be 0 and an underflow might occur when computing Idx-1.

[llvmbot]

@llvm/pr-subscribers-clang-tools-extra

@llvm/pr-subscribers-clang-tidy

Author: Zahira Ammarguellat (zahiraam)

Changes

If the range for llvm::any_of is empty, Idx will be 0 and an underflow might occur when computing Idx-1.

---

Full diff: https://github.com/llvm/llvm-project/pull/118528.diff

1 Files Affected:

• (modified) clang-tools-extra/clang-tidy/bugprone/CrtpConstructorAccessibilityCheck.cpp (+4-4)

diff --git a/clang-tools-extra/clang-tidy/bugprone/CrtpConstructorAccessibilityCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/CrtpConstructorAccessibilityCheck.cpp
index 8eaf54fe0088a4..ce307a2384aef7 100644
--- a/clang-tools-extra/clang-tidy/bugprone/CrtpConstructorAccessibilityCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/CrtpConstructorAccessibilityCheck.cpp
@@ -58,10 +58,10 @@ getDerivedParameter(const ClassTemplateSpecializationDecl *CRTP,
                Arg.getAsType()->getAsCXXRecordDecl() == Derived;
       });
 
-  return AnyOf ? CRTP->getSpecializedTemplate()
-                     ->getTemplateParameters()
-                     ->getParam(Idx - 1)
-               : nullptr;
+  return AnyOf && Idx > 0 ? CRTP->getSpecializedTemplate()
+                                ->getTemplateParameters()
+                                ->getParam(Idx - 1)
+                          : nullptr;
 }
 
 static std::vector<FixItHint>

[AaronBallman]

I don't think it's possible for AnyOf to be true and Idx to be 0 at the same time. Idx starts as zero, but the call to any_of on line 54 has a lambda which explicitly does ++Idx, so any_of cannot return true without incrementing Idx.

If this came from a static analysis tool, I would claim it's a false positive that doesn't require changes.

[zahiraam]

Even if the range is empty Idx will be incremented?

[AaronBallman]

If the range is empty, then Idx is not incremented, but AnyOf will be false.

[zahiraam]

Closing the PR then. Thanks.

[zahiraam]

Sorry for the noise.

[zahiraam]

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