clang/lib/Tooling/Inclusions/HeaderAnalysis.cpp

   1 //===--- HeaderAnalysis.cpp -------------------------------------*- C++ -*-===//
   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 "clang/Tooling/Inclusions/HeaderAnalysis.h"
  10 #include "clang/Basic/SourceLocation.h"
  11 #include "clang/Lex/HeaderSearch.h"
  12
  13 namespace clang::tooling {
  14 namespace {
  15
  16 // Is Line an #if or #ifdef directive?
  17 // FIXME: This makes headers with #ifdef LINUX/WINDOWS/MACOS marked as non
  18 // self-contained and is probably not what we want.
  19 bool isIf(llvm::StringRef Line) {
  20   Line = Line.ltrim();
  21   if (!Line.consume_front("#"))
  22     return false;
  23   Line = Line.ltrim();
  24   return Line.startswith("if");
  25 }
  26
  27 // Is Line an #error directive mentioning includes?
  28 bool isErrorAboutInclude(llvm::StringRef Line) {
  29   Line = Line.ltrim();
  30   if (!Line.consume_front("#"))
  31     return false;
  32   Line = Line.ltrim();
  33   if (!Line.startswith("error"))
  34     return false;
  35   return Line.contains_insensitive(
  36       "includ"); // Matches "include" or "including".
  37 }
  38
  39 // Heuristically headers that only want to be included via an umbrella.
  40 bool isDontIncludeMeHeader(StringRef Content) {
  41   llvm::StringRef Line;
  42   // Only sniff up to 100 lines or 10KB.
  43   Content = Content.take_front(100 * 100);
  44   for (unsigned I = 0; I < 100 && !Content.empty(); ++I) {
  45     std::tie(Line, Content) = Content.split('\n');
  46     if (isIf(Line) && isErrorAboutInclude(Content.split('\n').first))
  47       return true;
  48   }
  49   return false;
  50 }
  51
  52 bool isImportLine(llvm::StringRef Line) {
  53   Line = Line.ltrim();
  54   if (!Line.consume_front("#"))
  55     return false;
  56   Line = Line.ltrim();
  57   return Line.startswith("import");
  58 }
  59
  60 llvm::StringRef getFileContents(FileEntryRef FE, const SourceManager &SM) {
  61   return const_cast<SourceManager &>(SM)
  62       .getMemoryBufferForFileOrNone(FE)
  63       .value_or(llvm::MemoryBufferRef())
  64       .getBuffer();
  65 }
  66
  67 } // namespace
  68
  69 bool isSelfContainedHeader(FileEntryRef FE, const SourceManager &SM,
  70                            const HeaderSearch &HeaderInfo) {
  71   if (!HeaderInfo.isFileMultipleIncludeGuarded(FE) &&
  72       !HeaderInfo.hasFileBeenImported(FE) &&
  73       // Any header that contains #imports is supposed to be #import'd so no
  74       // need to check for anything but the main-file.
  75       (SM.getFileEntryForID(SM.getMainFileID()) != FE ||
  76        !codeContainsImports(getFileContents(FE, SM))))
  77     return false;
  78   // This pattern indicates that a header can't be used without
  79   // particular preprocessor state, usually set up by another header.
  80   return !isDontIncludeMeHeader(getFileContents(FE, SM));
  81 }
  82
  83 bool codeContainsImports(llvm::StringRef Code) {
  84   // Only sniff up to 100 lines or 10KB.
  85   Code = Code.take_front(100 * 100);
  86   llvm::StringRef Line;
  87   for (unsigned I = 0; I < 100 && !Code.empty(); ++I) {
  88     std::tie(Line, Code) = Code.split('\n');
  89     if (isImportLine(Line))
  90       return true;
  91   }
  92   return false;
  93 }
  94
  95 std::optional<StringRef> parseIWYUPragma(const char *Text) {
  96   // Skip the comment start, // or /*.
  97   if (Text[0] != '/' || (Text[1] != '/' && Text[1] != '*'))
  98     return std::nullopt;
  99   bool BlockComment = Text[1] == '*';
 100   Text += 2;
 101
 102   // Per spec, direcitves are whitespace- and case-sensitive.
 103   constexpr llvm::StringLiteral IWYUPragma = " IWYU pragma: ";
 104   if (strncmp(Text, IWYUPragma.data(), IWYUPragma.size()))
 105     return std::nullopt;
 106   Text += IWYUPragma.size();
 107   const char *End = Text;
 108   while (*End != 0 && *End != '\n')
 109     ++End;
 110   StringRef Rest(Text, End - Text);
 111   // Strip off whitespace and comment markers to avoid confusion. This isn't
 112   // fully-compatible with IWYU, which splits into whitespace-delimited tokens.
 113   if (BlockComment)
 114     Rest.consume_back("*/");
 115   return Rest.trim();
 116 }
 117
 118 } // namespace clang::tooling