Add -Wstring-plus-char, which warns when adding char literals to C strings.

Specifically, this warns when a character literal is added (using '+') to a
variable with type 'char *' (or any other pointer to character type). Like
-Wstring-plus-int, there is a fix-it to change "foo + 'a'" to "&foo['a']"
iff the character literal is on the right side of the string.

Patch by Anders Rönnholm!

llvm-svn: 193418

2 files changed, 47 insertions, 0 deletions

diff --git a/clang/test/Sema/string-plus-char.c b/clang/test/Sema/string-plus-char.c
new file mode 100644
index 00000000000..322e8f5962b
--- /dev/null
+++ b/clang/test/Sema/string-plus-char.c
@@ -0,0 +1,15 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+void f(const char *s) {
+  char *str = 0;
+  char *str2 = str + 'c'; // expected-warning {{adding 'char' to a string pointer does not append to the string}} expected-note {{use array indexing to silence this warning}}
+
+  const char *constStr = s + 'c'; // expected-warning {{adding 'char' to a string pointer does not append to the string}} expected-note {{use array indexing to silence this warning}}
+
+  str = 'c' + str;// expected-warning {{adding 'char' to a string pointer does not append to the string}} expected-note {{use array indexing to silence this warning}}
+
+  // no-warning
+  char c = 'c';
+  str = str + c;
+  str = c + str;
+}
diff --git a/clang/test/SemaCXX/string-plus-char.cpp b/clang/test/SemaCXX/string-plus-char.cpp
new file mode 100644
index 00000000000..00a2c4550dc
--- /dev/null
+++ b/clang/test/SemaCXX/string-plus-char.cpp
@@ -0,0 +1,32 @@
+// RUN: %clang_cc1 -fsyntax-only -std=c++11 -verify %s
+
+class A {
+public:
+  A(): str() { }
+  A(const char *p) { }
+  A(char *p) : str(p + 'a') { } // expected-warning {{adding 'char' to a string pointer does not append to the string}} expected-note {{use array indexing to silence this warning}}
+  A& operator+(const char *p) { return *this; }
+  A& operator+(char ch) { return *this; }
+  char * str;
+};
+
+void f(const char *s) {
+  A a = s + 'a'; // // expected-warning {{adding 'char' to a string pointer does not append to the string}} expected-note {{use array indexing to silence this warning}}
+  a = a + s + 'b'; // no-warning
+
+  char *str = 0;
+  char *str2 = str + 'c'; // expected-warning {{adding 'char' to a string pointer does not append to the string}} expected-note {{use array indexing to silence this warning}}
+
+  const char *constStr = s + 'c'; // expected-warning {{adding 'char' to a string pointer does not append to the string}} expected-note {{use array indexing to silence this warning}}
+
+  str = 'c' + str;// expected-warning {{adding 'char' to a string pointer does not append to the string}} expected-note {{use array indexing to silence this warning}}
+
+  wchar_t *wstr;
+  wstr = wstr + L'c'; // expected-warning {{adding 'wchar_t' to a string pointer does not append to the string}} expected-note {{use array indexing to silence this warning}}
+  str2 = str + u'a'; // expected-warning {{adding 'char16_t' to a string pointer does not append to the string}} expected-note {{use array indexing to silence this warning}}
+
+  // no-warning
+  char c = 'c';
+  str = str + c;
+  str = c + str;
+}