clang-tools-extra/clang-tidy/llvmlibc/CalleeNamespaceCheck.cpp

   1 //===-- CalleeNamespaceCheck.cpp ------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "CalleeNamespaceCheck.h"
  10 #include "NamespaceConstants.h"
  11 #include "clang/AST/ASTContext.h"
  12 #include "clang/ASTMatchers/ASTMatchFinder.h"
  13
  14 #include "clang/ASTMatchers/ASTMatchers.h"
  15 #include "llvm/ADT/StringSet.h"
  16
  17 using namespace clang::ast_matchers;
  18
  19 namespace clang::tidy::llvm_libc {
  20
  21 // Gets the outermost namespace of a DeclContext, right under the Translation
  22 // Unit.
  23 const DeclContext *getOutermostNamespace(const DeclContext *Decl) {
  24   const DeclContext *Parent = Decl->getParent();
  25   if (Parent->isTranslationUnit())
  26     return Decl;
  27   return getOutermostNamespace(Parent);
  28 }
  29
  30 void CalleeNamespaceCheck::registerMatchers(MatchFinder *Finder) {
  31   Finder->addMatcher(
  32       declRefExpr(to(functionDecl().bind("func"))).bind("use-site"), this);
  33 }
  34
  35 // A list of functions that are exempted from this check. The __errno_location
  36 // function is for setting errno, which is allowed in libc, and the other
  37 // functions are specifically allowed to be external so that they can be
  38 // intercepted.
  39 static const llvm::StringSet<> IgnoredFunctions = {
  40     "__errno_location", "malloc", "calloc", "realloc", "free", "aligned_alloc"};
  41
  42 void CalleeNamespaceCheck::check(const MatchFinder::MatchResult &Result) {
  43   const auto *UsageSiteExpr = Result.Nodes.getNodeAs<DeclRefExpr>("use-site");
  44   const auto *FuncDecl = Result.Nodes.getNodeAs<FunctionDecl>("func");
  45
  46   // Ignore compiler builtin functions.
  47   if (FuncDecl->getBuiltinID() != 0)
  48     return;
  49
  50   // If the outermost namespace of the function is a macro that starts with
  51   // __llvm_libc, we're good.
  52   const auto *NS = dyn_cast<NamespaceDecl>(getOutermostNamespace(FuncDecl));
  53   if (NS && Result.SourceManager->isMacroBodyExpansion(NS->getLocation()) &&
  54       NS->getName().starts_with(RequiredNamespaceRefStart))
  55     return;
  56
  57   const DeclarationName &Name = FuncDecl->getDeclName();
  58   if (Name.isIdentifier() &&
  59       IgnoredFunctions.contains(Name.getAsIdentifierInfo()->getName()))
  60     return;
  61
  62   diag(UsageSiteExpr->getBeginLoc(),
  63        "%0 must resolve to a function declared "
  64        "within the namespace defined by the '%1' macro")
  65       << FuncDecl << RequiredNamespaceRefMacroName;
  66
  67   diag(FuncDecl->getLocation(), "resolves to this declaration",
  68        clang::DiagnosticIDs::Note);
  69 }
  70
  71 } // namespace clang::tidy::llvm_libc