flatc -M: escape make-special characters in depfiles

include/flatbuffers/util.h

@@ -473,6 +473,11 @@ FLATBUFFERS_CONSTEXPR char kPathSeparator = '/';
 // Returns the path with the extension, if any, removed.
 std::string StripExtension(const std::string& filepath);
 
+// Escapes characters that are special to make in a filename, so the name can
+// be emitted into a make dependency rule. Mirrors how gcc and clang emit
+// -M/-MD depfiles.
+std::string EscapeMakeDep(const std::string& filepath);
+
 // Returns the extension, if any.
 std::string GetExtension(const std::string& filepath);
 

src/code_generators.cpp

@@ -42,7 +42,7 @@ std::string JavaCSharpMakeRule(const bool java, const Parser& parser,
     if (!make_rule.empty()) make_rule += " ";
     std::string directory =
         BaseGenerator::NamespaceDir(parser, path, *enum_def.defined_namespace);
-    make_rule += directory + enum_def.name + file_extension;
+    make_rule += EscapeMakeDep(directory + enum_def.name + file_extension);
   }
 
   for (auto it = parser.structs_.vec.begin(); it != parser.structs_.vec.end();
@@ -51,13 +51,13 @@ std::string JavaCSharpMakeRule(const bool java, const Parser& parser,
     if (!make_rule.empty()) make_rule += " ";
     std::string directory = BaseGenerator::NamespaceDir(
         parser, path, *struct_def.defined_namespace);
-    make_rule += directory + struct_def.name + file_extension;
+    make_rule += EscapeMakeDep(directory + struct_def.name + file_extension);
   }
 
   make_rule += ": ";
   auto included_files = parser.GetIncludedFilesRecursive(file_name);
   for (auto it = included_files.begin(); it != included_files.end(); ++it) {
-    make_rule += " " + *it;
+    make_rule += " " + EscapeMakeDep(*it);
   }
   return make_rule;
 }

src/flatc.cpp

@@ -957,8 +957,9 @@ std::unique_ptr<Parser> FlatCompiler::GenerateCode(const FlatCOptions& options,
         const CodeGenerator::Status status = code_generator->GenerateMakeRule(
             *parser, options.output_path, filename, make_rule);
         if (status == CodeGenerator::Status::OK && !make_rule.empty()) {
-          printf("%s\n",
-                 flatbuffers::WordWrap(make_rule, 80, " ", " \\").c_str());
+          // Emit the rule as a single line. Depfiles are line-oriented and
+          // word-wrapping would split escaped filenames.
+          printf("%s\n", make_rule.c_str());
         } else {
           Error("Cannot generate make rule for " +
                 code_generator->LanguageName());

src/idl_gen_binary.cpp

@@ -61,12 +61,12 @@ static std::string BinaryMakeRule(const Parser& parser, const std::string& path,
   if (!parser.builder_.GetSize()) return "";
   std::string filebase =
       flatbuffers::StripPath(flatbuffers::StripExtension(file_name));
-  std::string make_rule =
-      BinaryFileName(parser, path, filebase) + ": " + file_name;
+  std::string make_rule = EscapeMakeDep(BinaryFileName(parser, path, filebase)) +
+                          ": " + EscapeMakeDep(file_name);
   auto included_files =
       parser.GetIncludedFilesRecursive(parser.root_struct_def_->file);
   for (auto it = included_files.begin(); it != included_files.end(); ++it) {
-    make_rule += " " + *it;
+    make_rule += " " + EscapeMakeDep(*it);
   }
   return make_rule;
 }

src/idl_gen_cpp.cpp

@@ -4546,9 +4546,10 @@ static std::string CPPMakeRule(const Parser& parser, const std::string& path,
   cpp::CppGenerator geneartor(parser, path, file_name, parser.opts);
   const auto included_files = parser.GetIncludedFilesRecursive(file_name);
   std::string make_rule =
-      geneartor.GeneratedFileName(path, filebase, parser.opts) + ": ";
+      EscapeMakeDep(geneartor.GeneratedFileName(path, filebase, parser.opts)) +
+      ": ";
   for (const std::string& included_file : included_files) {
-    make_rule += " " + included_file;
+    make_rule += " " + EscapeMakeDep(included_file);
   }
   return make_rule;
 }

src/idl_gen_dart.cpp

@@ -1152,11 +1152,11 @@ static std::string DartMakeRule(const Parser& parser, const std::string& path,
   auto filebase =
       flatbuffers::StripPath(flatbuffers::StripExtension(file_name));
   dart::DartGenerator generator(parser, path, file_name);
-  auto make_rule = generator.Filename("") + ": ";
+  auto make_rule = EscapeMakeDep(generator.Filename("")) + ": ";
 
   auto included_files = parser.GetIncludedFilesRecursive(file_name);
   for (auto it = included_files.begin(); it != included_files.end(); ++it) {
-    make_rule += " " + *it;
+    make_rule += " " + EscapeMakeDep(*it);
   }
   return make_rule;
 }

src/idl_gen_rust.cpp

@@ -3213,11 +3213,12 @@ static std::string RustMakeRule(const Parser& parser, const std::string& path,
       flatbuffers::StripPath(flatbuffers::StripExtension(file_name));
   rust::RustGenerator generator(parser, path, file_name);
   std::string make_rule =
-      generator.GeneratedFileName(path, filebase, parser.opts) + ": ";
+      EscapeMakeDep(generator.GeneratedFileName(path, filebase, parser.opts)) +
+      ": ";
 
   auto included_files = parser.GetIncludedFilesRecursive(file_name);
   for (auto it = included_files.begin(); it != included_files.end(); ++it) {
-    make_rule += " " + *it;
+    make_rule += " " + EscapeMakeDep(*it);
   }
   return make_rule;
 }

src/idl_gen_text.cpp

@@ -461,11 +461,13 @@ static std::string TextMakeRule(const Parser& parser, const std::string& path,
   if (!parser.builder_.GetSize() || !parser.root_struct_def_) return "";
   std::string filebase =
       flatbuffers::StripPath(flatbuffers::StripExtension(file_name));
-  std::string make_rule = TextFileName(path, filebase) + ": " + file_name;
+  std::string make_rule =
+      EscapeMakeDep(TextFileName(path, filebase)) + ": " +
+      EscapeMakeDep(file_name);
   auto included_files =
       parser.GetIncludedFilesRecursive(parser.root_struct_def_->file);
   for (auto it = included_files.begin(); it != included_files.end(); ++it) {
-    make_rule += " " + *it;
+    make_rule += " " + EscapeMakeDep(*it);
   }
   return make_rule;
 }

src/idl_gen_ts.cpp

@@ -2405,11 +2405,12 @@ static std::string TSMakeRule(const Parser& parser, const std::string& path,
       flatbuffers::StripPath(flatbuffers::StripExtension(file_name));
   ts::TsGenerator generator(parser, path, file_name);
   std::string make_rule =
-      generator.GeneratedFileName(path, filebase, parser.opts) + ": ";
+      EscapeMakeDep(generator.GeneratedFileName(path, filebase, parser.opts)) +
+      ": ";
 
   auto included_files = parser.GetIncludedFilesRecursive(file_name);
   for (auto it = included_files.begin(); it != included_files.end(); ++it) {
-    make_rule += " " + *it;
+    make_rule += " " + EscapeMakeDep(*it);
   }
   return make_rule;
 }

src/util.cpp

@@ -273,6 +273,22 @@ std::string StripExtension(const std::string& filepath) {
   return i != std::string::npos ? filepath.substr(0, i) : filepath;
 }
 
+std::string EscapeMakeDep(const std::string& filepath) {
+  std::string escaped;
+  escaped.reserve(filepath.size() * 2);
+  for (const char c : filepath) {
+    switch (c) {
+      case '\\': escaped += "\\\\"; break;
+      case ' ': escaped += "\\ "; break;
+      case '#': escaped += "\\#"; break;
+      case ':': escaped += "\\:"; break;
+      case '$': escaped += "$$"; break;
+      default: escaped += c; break;
+    }
+  }
+  return escaped;
+}
+
 std::string GetExtension(const std::string& filepath) {
   size_t i = filepath.find_last_of('.');
   return i != std::string::npos ? filepath.substr(i + 1) : "";

tests/test.cpp

@@ -1799,6 +1799,7 @@ int FlatBufferTests(const std::string& tests_data_path) {
 #endif
 
   UtilConvertCase();
+  EscapeMakeDepTest();
 
   FuzzTest1();
   FuzzTest2();

tests/util_test.cpp

@@ -169,5 +169,24 @@ void UtilConvertCase() {
   }
 }
 
+void EscapeMakeDepTest() {
+  // Characters special to make must be escaped, backslash first.
+  TEST_EQ(std::string("\\\\"), flatbuffers::EscapeMakeDep("\\"));
+  TEST_EQ(std::string("\\ "), flatbuffers::EscapeMakeDep(" "));
+  TEST_EQ(std::string("\\#"), flatbuffers::EscapeMakeDep("#"));
+  TEST_EQ(std::string("\\:"), flatbuffers::EscapeMakeDep(":"));
+  TEST_EQ(std::string("$$"), flatbuffers::EscapeMakeDep("$"));
+  // Combined special characters.
+  TEST_EQ(std::string("a\\ b\\#c\\:d$$e"),
+          flatbuffers::EscapeMakeDep("a b#c:d$e"));
+  // Trailing backslash.
+  TEST_EQ(std::string("name\\\\"), flatbuffers::EscapeMakeDep("name\\"));
+  // Empty string unchanged.
+  TEST_EQ(std::string(""), flatbuffers::EscapeMakeDep(""));
+  // Ordinary filenames are untouched.
+  TEST_EQ(std::string("dir/file.fbs"),
+          flatbuffers::EscapeMakeDep("dir/file.fbs"));
+}
+
 }  // namespace tests
 }  // namespace flatbuffers

tests/util_test.h

@@ -7,6 +7,7 @@ namespace tests {
 void NumericUtilsTest();
 void IsAsciiUtilsTest();
 void UtilConvertCase();
+void EscapeMakeDepTest();
 
 }  // namespace tests
 }  // namespace flatbuffers