implement r-lib#432

Author: pachadotdev

cpp11test/DESCRIPTION

@@ -20,4 +20,4 @@ Suggests:
     xml2
 LazyData: true
 Roxygen: list(markdown = TRUE)
-RoxygenNote: 7.1.1
+RoxygenNote: 7.3.2

inst/include/cpp11/as.hpp

@@ -184,8 +184,14 @@ template <typename T>
 enable_if_c_string<T, T> as_cpp(SEXP from) {
   if (Rf_isString(from)) {
     if (Rf_xlength(from) == 1) {
-      // TODO: use vmaxget / vmaxset here?
-      return {unwind_protect([&] { return Rf_translateCharUTF8(STRING_ELT(from, 0)); })};
+      void* vmax = vmaxget();
+
+      const char* result =
+          unwind_protect([&] { return Rf_translateCharUTF8(STRING_ELT(from, 0)); });
+
+      vmaxset(vmax);
+
+      return {result};
     }
   }