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