[clang] Diagnose problematic uses of constructor/destructor attribute (PR #67673)

[Nick Desaulniers via cfe-commits]

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@@ -2352,26 +2352,126 @@ static void handleUnusedAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
   D->addAttr(::new (S.Context) UnusedAttr(S.Context, AL));
 }
 
-static void handleConstructorAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
-  uint32_t priority = ConstructorAttr::DefaultPriority;
+static void diagnoseInvalidPriority(Sema &S, uint32_t Priority,
+                                    const ParsedAttr &A,
+                                    SourceLocation PriorityLoc) {
+  constexpr uint32_t ReservedPriorityLower = 101, ReservedPriorityUpper = 65535;
+
+  // Only perform the priority check if the attribute is outside of a system
+  // header. Values <= 100 are reserved for the implementation, and libc++
+  // benefits from being able to specify values in that range. Values > 65535
+  // are reserved for historical reasons.
+  if ((Priority < ReservedPriorityLower || Priority > ReservedPriorityUpper) &&
+      !S.getSourceManager().isInSystemHeader(A.getLoc())) {
+    S.Diag(A.getLoc(), diag::warn_priority_out_of_range)
+        << PriorityLoc << A << ReservedPriorityLower << ReservedPriorityUpper;
+  }
+}
+
+static bool FunctionParamsAreMainLike(ASTContext &Context,
+                                      const FunctionDecl *FD) {
+  assert(FD->hasPrototype() && "expected the function to have a prototype");
+  const auto *FPT = FD->getType()->castAs<FunctionProtoType>();
+  QualType CharPP =
+      Context.getPointerType(Context.getPointerType(Context.CharTy));
+  QualType Expected[] = {Context.IntTy, CharPP, CharPP, CharPP};
+
+  for (unsigned I = 0; I < FPT->getNumParams(); ++I) {
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nickdesaulniers wrote:

I'm worries about the expression `Expected[I]` going out of bounds below. I think if you add `&& I < 4` to the loop condition that might be an additional safeguard.

https://github.com/llvm/llvm-project/pull/67673