[clang] [-Wunsafe-buffer-usage] Introduce std::array fixits (PR #80084)

[via cfe-commits]

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@@ -2495,10 +2470,113 @@ static FixItList fixVariableWithSpan(const VarDecl *VD,
   return fixLocalVarDeclWithSpan(VD, Ctx, getUserFillPlaceHolder(), Handler);
 }
 
+static FixItList fixVarDeclWithArray(const VarDecl *D, const ASTContext &Ctx,
+                                     UnsafeBufferUsageHandler &Handler) {
+  FixItList FixIts{};
+
+  if (auto CAT = dyn_cast<clang::ConstantArrayType>(D->getType())) {
+    const QualType &ArrayEltT = CAT->getElementType();
+    assert(!ArrayEltT.isNull() && "Trying to fix a non-array type variable!");
+
+    // For most types the transformation is simple:
+    //   T foo[10]; => std::array<T, 10> foo;
+    // Cv-specifiers are straigtforward:
+    //   const T foo[10]; => std::array<const T, 10> foo;
+    // Pointers are straightforward:
+    //   T * foo[10]; => std::array<T *, 10> foo;
+    //
+    // However, for const pointers the transformation is different:
+    //   T * const foo[10]; => const std::array<T *, 10> foo;
+    if (ArrayEltT->isPointerType() && ArrayEltT.isConstQualified()) {
+      DEBUG_NOTE_DECL_FAIL(D, " : const size array of const pointers");
+      // FIXME: implement the support
+      // FIXME: bail if the const pointer is a typedef
+      return {};
+    }
+
+    const SourceLocation IdentifierLoc = getVarDeclIdentifierLoc(D);
+
+    // Get the spelling of the element type as written in the source file
+    // (including macros, etc.).
+    auto MaybeElemTypeTxt =
+        getRangeText({D->getBeginLoc(), IdentifierLoc}, Ctx.getSourceManager(),
+                     Ctx.getLangOpts());
+    if (!MaybeElemTypeTxt)
+      return {};
+    const llvm::StringRef ElemTypeTxt = MaybeElemTypeTxt->trim();
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jkorous-apple wrote:

For now I would leave it as is but if we later find that callers need to trim so often it gets annoying then let's reconsider.

https://github.com/llvm/llvm-project/pull/80084