================
@@ -238,3 +246,69 @@ void f(Scoped1 S1, Scoped2 S2) {
}
#endif
+
+#if __cplusplus >= 202000L
+class my_string {
+ char *data;
+ unsigned size;
+
+public:
+ template<unsigned N>
+ constexpr my_string(const char (&literal)[N]) {
+ data = new char[N+1];
+ for (size = 0; size < N; ++size) {
+ data[size] = literal[size];
+ if (data[size] == 0)
+ break;
+ }
+ data[size] = 0;
+ }
+
+ my_string(const my_string &) = delete;
+
+ constexpr my_string(my_string &&that) {
+ data = that.data;
+ size = that.size;
+ that.data = nullptr;
+ that.size = 0;
+ }
+
+ constexpr ~my_string() {
+ delete[] data;
+ }
+
+ template<unsigned N>
+ constexpr void append(const char (&literal)[N]) {
+ char *cat = new char[size + N + 1];
+ char *tmp = cat;
+ for (unsigned i = 0; i < size; ++i) {
+ *tmp++ = data[i];
+ }
+ for (unsigned i = 0; i < N; ++i) {
+ *tmp = literal[i];
+ if (*tmp == 0)
+ break;
+ ++tmp;
+ }
+ *tmp = 0;
+ delete[] data;
+ size = tmp - cat;
+ data = cat;
+ }
+
+ constexpr const char *c_str() const {
+ return data;
+ }
+};
+
+constexpr my_string const_string() {
+ my_string str("hello %s");
+ str.append(", %d");
+ return str;
+}
+
+void test_constexpr_string() {
+ printf(const_string().c_str(), "hello", 123); // no-warning
+ printf(const_string().c_str(), 123, 456); // expected-warning {{format
specifies type 'char *' but the argument has type 'int'}}
+}
+#endif
----------------
hubert-reinterpretcast wrote:
See https://github.com/llvm/llvm-project/issues/135913 for other potential
considerations.
https://github.com/llvm/llvm-project/pull/135864
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