Merge branch 'master' into smart_holder

include/pybind11/attr.h

@@ -377,7 +377,7 @@ template <> struct process_attribute<is_new_style_constructor> : process_attribu
 };
 
 inline void process_kw_only_arg(const arg &a, function_record *r) {
-    if (!a.name || strlen(a.name) == 0)
+    if (!a.name || a.name[0] == '\0')
         pybind11_fail("arg(): cannot specify an unnamed argument after an kw_only() annotation");
     ++r->nargs_kw_only;
 }

include/pybind11/pybind11.h

@@ -444,7 +444,7 @@ protected:
                 signatures += it->signature;
                 signatures += "\n";
             }
-            if (it->doc && strlen(it->doc) > 0 && options::show_user_defined_docstrings()) {
+            if (it->doc && it->doc[0] != '\0' && options::show_user_defined_docstrings()) {
                 // If we're appending another docstring, and aren't printing function signatures, we
                 // need to append a newline first:
                 if (!options::show_function_signatures()) {

include/pybind11/stl.h

@@ -380,7 +380,11 @@ struct type_caster<std::variant<Ts...>> : variant_caster<std::variant<Ts...>> {
 PYBIND11_NAMESPACE_END(detail)
 
 inline std::ostream &operator<<(std::ostream &os, const handle &obj) {
+#ifdef PYBIND11_HAS_STRING_VIEW
+    os << str(obj).cast<std::string_view>();
+#else
     os << (std::string) str(obj);
+#endif
     return os;
 }