[clang-tidy] Make readability-string-compare check use <string> header

[mikecrowe]

Summary

Improve the generic <string> header by adding another constructor,
std::basic_string::empty and operator!= overload set so that it can be
used to replace the custom implementation in the
readability-string-compare check.

Depends on D145311

[carlosgalvezp]

clang-tools-extra/test/clang-tidy/checkers/readability/string-compare.cpp

4–8

Would it make sense to add these to the new header?

[mikecrowe]

clang-tools-extra/test/clang-tidy/checkers/readability/string-compare.cpp

4–8

Done in https://reviews.llvm.org/D145724 .

[PiotrZSL]

LGTM

[carlosgalvezp]

@PiotrZSL I believe you have landed some patches of this chain. Would you mind sharing how you do it? I'm not an expert in Phabricator and simply doing arc patch D145312 leads to cherry-pick conflicts, and when I solve them I don't end up having this patch as HEAD. With this knowledge I will be able to help out closing these patches!

[carlosgalvezp]

@mikecrowe I seems I cannot land this until it's rebased on top of main, would you be able to do that? Thanks!

[PiotrZSL]

In D145312#4187195, @carlosgalvezp wrote:

@PiotrZSL I believe you have landed some patches of this chain. Would you mind sharing how you do it? I'm not an expert in Phabricator and simply doing arc patch D145312 leads to cherry-pick conflicts, and when I solve them I don't end up having this patch as HEAD. With this knowledge I will be able to help out closing these patches!

arc patch --nobranch --skip-dependencies D145312
I will push them...

[carlosgalvezp]

In D145312#4187247, @PiotrZSL wrote:

In D145312#4187195, @carlosgalvezp wrote:

@PiotrZSL I believe you have landed some patches of this chain. Would you mind sharing how you do it? I'm not an expert in Phabricator and simply doing arc patch D145312 leads to cherry-pick conflicts, and when I solve them I don't end up having this patch as HEAD. With this knowledge I will be able to help out closing these patches!

arc patch --nobranch --skip-dependencies D145312
I will push them...

Ahh that was it, thank you!

clang-tools-extra/test/clang-tidy/checkers/Inputs/Headers/string

 template <typename T>
 class char_traits {};
 template <typename C, typename T, typename A>
 struct basic_string {
   typedef size_t size_type;
   typedef basic_string<C, T, A> _Type;
   basic_string();
   basic_string(const C *p, const A &a = A());
+  basic_string(const C *p, size_type count);
 
   ~basic_string();
 
   const C *c_str() const;
   const C *data() const;
 
+  bool empty() const;
+
   _Type& append(const C *s);
   _Type& append(const C *s, size_type n);
   _Type& assign(const C *s);
   _Type& assign(const C *s, size_type n);
 
   int compare(const _Type&) const;
   int compare(const C* s) const;
   int compare(size_type pos, size_type len, const _Type&) const;

 
 std::string operator+(const std::string&, const std::string&);
 std::string operator+(const std::string&, const char*);
 std::string operator+(const char*, const std::string&);
 
 bool operator==(const std::string&, const std::string&);
 bool operator==(const std::string&, const char*);
 bool operator==(const char*, const std::string&);
+
+bool operator!=(const std::string&, const std::string&);
+bool operator!=(const std::string&, const char*);
+bool operator!=(const char*, const std::string&);
 }
 
 #endif // _STRING_

clang-tools-extra/test/clang-tidy/checkers/readability/string-compare.cpp

-// RUN: %check_clang_tidy %s readability-string-compare %t
-
-namespace std {
-template <typename T>
-class allocator {};
-template <typename T>
-class char_traits {};
-template <typename C, typename T = std::char_traits<C>, typename A = std::allocator<C>>
-class basic_string {
-public:
-  basic_string();
-  basic_string(const C *, unsigned int size);
-  int compare(const basic_string<char> &str) const;
-  int compare(const C *) const;
-  int compare(int, int, const basic_string<char> &str) const;
-  bool empty();
-};
-bool operator==(const basic_string<char> &lhs, const basic_string<char> &rhs);
-bool operator!=(const basic_string<char> &lhs, const basic_string<char> &rhs);
-bool operator==(const basic_string<char> &lhs, const char *&rhs);
-typedef basic_string<char> string;
-}
+// RUN: %check_clang_tidy %s readability-string-compare %t -- -- -isystem %clang_tidy_headers
+#include <string>
 
 void func(bool b);
 
 std::string comp() {
   std::string str("a", 1);
   return str;
 }