[clang] [clang] "modular_format" attribute for functions using format strings (PR #147431)

[Daniel Thornburgh via cfe-commits]

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@@ -6973,6 +6973,73 @@ static void handleVTablePointerAuthentication(Sema &S, Decl *D,
       CustomDiscriminationValue));
 }
 
+static bool modularFormatAttrsEquiv(const ModularFormatAttr *Existing,
+                                    IdentifierInfo *ModularImplFn,
+                                    StringRef ImplName,
+                                    ArrayRef<StringRef> Aspects) {
+  return Existing->getModularImplFn() == ModularImplFn &&
+         Existing->getImplName() == ImplName &&
+         Existing->aspects_size() == Aspects.size() &&
+         llvm::equal(Existing->aspects(), Aspects);
+}
+
+ModularFormatAttr *
+Sema::mergeModularFormatAttr(Decl *D, const AttributeCommonInfo &CI,
+                             IdentifierInfo *ModularImplFn, StringRef ImplName,
+                             MutableArrayRef<StringRef> Aspects) {
+  if (const auto *Existing = D->getAttr<ModularFormatAttr>()) {
+    if (!modularFormatAttrsEquiv(Existing, ModularImplFn, ImplName, Aspects)) {
+      Diag(Existing->getLocation(), diag::err_duplicate_attribute) << *Existing;
+      Diag(CI.getLoc(), diag::note_conflicting_attribute);
+    }
+    // Drop the existing attribute on the declaration in favor of the newly
+    // inherited one.
+    D->dropAttr<ModularFormatAttr>();
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mysterymath wrote:

Done.

https://github.com/llvm/llvm-project/pull/147431