[clang] [-Wunsafe-buffer-usage] Ignore constant safe indices in array subscripts (PR #80504)

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<!--LLVM CODE FORMAT COMMENT: {clang-format}-->


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``````````bash
git-clang-format --diff 86cd2fbdfe67d70a7fe061ed5d3a644f50f070f5 b510cf7ca8c47c64e0b9f5fcd5634759dfe95751 -- clang/test/SemaCXX/warn-unsafe-buffer-usage-array.cpp clang/test/SemaCXX/warn-unsafe-buffer-usage-fixits-local-var-array.cpp clang/test/SemaCXX/warn-unsafe-buffer-usage-fixits-pointer-arg-to-func-ptr-call.cpp clang/include/clang/Analysis/Analyses/UnsafeBufferUsage.h clang/lib/Analysis/UnsafeBufferUsage.cpp clang/lib/Sema/AnalysisBasedWarnings.cpp clang/test/SemaCXX/warn-unsafe-buffer-usage-debug.cpp clang/test/SemaCXX/warn-unsafe-buffer-usage-fixits-pointer-access.cpp clang/test/SemaCXX/warn-unsafe-buffer-usage.cpp
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View the diff from clang-format here.
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``````````diff
diff --git a/clang/lib/Analysis/UnsafeBufferUsage.cpp b/clang/lib/Analysis/UnsafeBufferUsage.cpp
index 8f8751f4ee..4399d15f46 100644
--- a/clang/lib/Analysis/UnsafeBufferUsage.cpp
+++ b/clang/lib/Analysis/UnsafeBufferUsage.cpp
@@ -281,10 +281,10 @@ isInUnspecifiedPointerContext(internal::Matcher<Stmt> InnerMatcher) {
   // 4. the operand of a pointer subtraction operation
   //    (i.e., computing the distance between two pointers); or ...
 
-  auto CallArgMatcher =
-      callExpr(forEachArgumentWithParamType(InnerMatcher,
-                  isAnyPointer() /* array also decays to pointer type*/),
-          unless(callee(functionDecl(hasAttr(attr::UnsafeBufferUsage)))));
+  auto CallArgMatcher = callExpr(
+      forEachArgumentWithParamType(
+          InnerMatcher, isAnyPointer() /* array also decays to pointer type*/),
+      unless(callee(functionDecl(hasAttr(attr::UnsafeBufferUsage)))));
 
   auto CastOperandMatcher =
       castExpr(anyOf(hasCastKind(CastKind::CK_PointerToIntegral),
@@ -404,7 +404,8 @@ AST_MATCHER(CXXConstructExpr, isSafeSpanTwoParamConstruct) {
 }
 
 AST_MATCHER(ArraySubscriptExpr, isSafeArraySubscript) {
-  const DeclRefExpr * BaseDRE = dyn_cast_or_null<DeclRefExpr>(Node.getBase()->IgnoreParenImpCasts());
+  const DeclRefExpr *BaseDRE =
+      dyn_cast_or_null<DeclRefExpr>(Node.getBase()->IgnoreParenImpCasts());
   if (!BaseDRE)
     return false;
   if (!BaseDRE->getDecl())
@@ -412,15 +413,17 @@ AST_MATCHER(ArraySubscriptExpr, isSafeArraySubscript) {
   auto BaseVarDeclTy = BaseDRE->getDecl()->getType();
   if (!BaseVarDeclTy->isConstantArrayType())
     return false;
-  const auto * CATy = dyn_cast_or_null<ConstantArrayType>(BaseVarDeclTy);
+  const auto *CATy = dyn_cast_or_null<ConstantArrayType>(BaseVarDeclTy);
   if (!CATy)
     return false;
   const APInt ArrSize = CATy->getSize();
 
-  if (const auto * IdxLit = dyn_cast<IntegerLiteral>(Node.getIdx())) {
+  if (const auto *IdxLit = dyn_cast<IntegerLiteral>(Node.getIdx())) {
     const APInt ArrIdx = IdxLit->getValue();
-    // FIXME: ArrIdx.isNegative() we could immediately emit an error as that's a bug
-    if (ArrIdx.isNonNegative() && ArrIdx.getLimitedValue() < ArrSize.getLimitedValue())
+    // FIXME: ArrIdx.isNegative() we could immediately emit an error as that's a
+    // bug
+    if (ArrIdx.isNonNegative() &&
+        ArrIdx.getLimitedValue() < ArrSize.getLimitedValue())
       return true;
   }
 

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https://github.com/llvm/llvm-project/pull/80504