[clang] [clang] Catch missing format attributes (PR #105479)

[via cfe-commits]

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@@ -5918,6 +5918,181 @@ static void handlePreferredTypeAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
   D->addAttr(::new (S.Context) PreferredTypeAttr(S.Context, AL, ParmTSI));
 }
 
+// Diagnosing missing format attributes is implemented in two steps:
+// 1. Detect missing format attributes while checking function calls.
+// 2. Emit diagnostic in part that processes function body.
+// For this purpose it is created vector that stores information about format
+// attributes. There are no two format attributes with same arguments in a
+// vector. Vector could contains attributes that only store information about
+// format type (format string and first to check argument are set to -1).
+namespace {
+std::vector<FormatAttr *> MissingAttributes;
+} // end anonymous namespace
+
+// This function is called only if function call is not inside template body.
+// TODO: Add call for function calls inside template body.
+// Detects and stores missing format attributes in a vector.
+void Sema::DetectMissingFormatAttributes(const FunctionDecl *Callee,
+                                         ArrayRef<const Expr *> Args,
+                                         SourceLocation Loc) {
+  assert(Callee);
+
+  // If there is no caller, exit.
+  const FunctionDecl *Caller = getCurFunctionDecl();
+  if (!getCurFunctionDecl())
+    return;
+
+  // Check if callee function is a format function.
+  // If it is, check if caller function misses format attributes.
+
+  if (!Callee->hasAttr<FormatAttr>())
+    return;
+
+  // va_list is not intended to be passed to variadic function.
+  if (Callee->isVariadic())
+    return;
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apple-fcloutier wrote:

I think that there's just one code base in the world that does it, but Clang supports multiple format attributes on the same function, where one of them has a non-zero format index and any others pass a va_list. See https://github.com/llvm/llvm-project/pull/129954. In that context, bailing out because the function is variadic is too eager.

https://github.com/llvm/llvm-project/pull/105479