[clang-tidy] add new checker for string literal with NUL character.

Summary:
This patch adds the support for detecting suspicious string
literals and their //incorrect// usage.

The following example shows a incorrect character escaping leading 
to an embedded NUL character. 
```
  std::string str = "\0x42";   // Should be "\x42".
```

The patch also add detection of truncated literal when a literal
is passed to a string constructor.

Reviewers: hokein, alexfh

Subscribers: LegalizeAdulthood, bcraig, Eugene.Zelenko, bkramer, cfe-commits

Differential Revision: http://reviews.llvm.org/D18783

llvm-svn: 265691

1 files changed, 85 insertions, 0 deletions

diff --git a/clang-tools-extra/test/clang-tidy/misc-string-literal-with-embedded-nul.cpp b/clang-tools-extra/test/clang-tidy/misc-string-literal-with-embedded-nul.cpp
new file mode 100644
index 00000000000..2605dd4eccb
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/misc-string-literal-with-embedded-nul.cpp
@@ -0,0 +1,85 @@
+// RUN: %check_clang_tidy %s misc-string-literal-with-embedded-nul %t
+
+namespace std {
+template <typename T>
+class allocator {};
+template <typename T>
+class char_traits {};
+template <typename C, typename T, typename A>
+struct basic_string {
+  typedef basic_string<C, T, A> _Type;
+  basic_string();
+  basic_string(const C *p, const A &a = A());
+
+  _Type& operator+=(const C* s);
+  _Type& operator=(const C* s);
+};
+
+typedef basic_string<char, std::char_traits<char>, std::allocator<char>> string;
+typedef basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t>> wstring;
+}
+
+bool operator==(const std::string&, const char*);
+bool operator==(const char*, const std::string&);
+
+
+const char Valid[] = "This is valid \x12.";
+const char Strange[] = "This is strange \0x12 and must be fixed";
+// CHECK-MESSAGES: :[[@LINE-1]]:24: warning: suspicious embedded NUL character [misc-string-literal-with-embedded-nul]
+
+const char textA[] = "\0x01\0x02\0x03\0x04";
+// CHECK-MESSAGES: :[[@LINE-1]]:22: warning: suspicious embedded NUL character
+const wchar_t textW[] = L"\0x01\0x02\0x03\0x04";
+// CHECK-MESSAGES: :[[@LINE-1]]:25: warning: suspicious embedded NUL character
+
+const char A[] = "\0";
+const char B[] = "\0x";
+const char C[] = "\0x1";
+const char D[] = "\0x11";
+// CHECK-MESSAGES: :[[@LINE-1]]:18: warning: suspicious embedded NUL character
+
+const wchar_t E[] = L"\0";
+const wchar_t F[] = L"\0x";
+const wchar_t G[] = L"\0x1";
+const wchar_t H[] = L"\0x11";
+// CHECK-MESSAGES: :[[@LINE-1]]:21: warning: suspicious embedded NUL character
+
+const char I[] = "\000\000\000\000";
+const char J[] = "\0\0\0\0\0\0";
+const char K[] = "";
+
+const char L[] = "\0x12" "\0x12" "\0x12" "\0x12";
+// CHECK-MESSAGES: :[[@LINE-1]]:18: warning: suspicious embedded NUL character
+
+void TestA() {
+  std::string str1 = "abc\0def";
+  // CHECK-MESSAGES: :[[@LINE-1]]:22: warning: truncated string literal
+  std::string str2 = "\0";
+  // CHECK-MESSAGES: :[[@LINE-1]]:22: warning: truncated string literal
+  std::string str3("\0");
+  // CHECK-MESSAGES: :[[@LINE-1]]:20: warning: truncated string literal
+  std::string str4{"\x00\x01\x02\x03"};
+  // CHECK-MESSAGES: :[[@LINE-1]]:20: warning: truncated string literal
+
+  std::string str;
+  str += "abc\0def";
+  // CHECK-MESSAGES: :[[@LINE-1]]:10: warning: truncated string literal
+  str = "abc\0def";
+  // CHECK-MESSAGES: :[[@LINE-1]]:9: warning: truncated string literal
+
+  if (str == "abc\0def") return;
+  // CHECK-MESSAGES: :[[@LINE-1]]:14: warning: truncated string literal
+  if ("abc\0def" == str) return;
+  // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: truncated string literal
+}
+
+void TestW() {
+  std::wstring str1 = L"abc\0def";
+  // CHECK-MESSAGES: :[[@LINE-1]]:23: warning: truncated string literal
+  std::wstring str2 = L"\0";
+  // CHECK-MESSAGES: :[[@LINE-1]]:23: warning: truncated string literal
+  std::wstring str3(L"\0");
+  // CHECK-MESSAGES: :[[@LINE-1]]:21: warning: truncated string literal
+  std::wstring str4{L"\x00\x01\x02\x03"};
+  // CHECK-MESSAGES: :[[@LINE-1]]:21: warning: truncated string literal
+}