Fix util::ostringstream, fix pretty-printing, stub out new globals

luprex/cpp/drv/drvutil.hpp

@@ -68,23 +68,27 @@ double get_monotonic_clock();
 // without copying, use oss.size() and oss.c_str()
 //
 class ostringstream : public std::ostringstream {
-    class rstringbuf : public std::stringbuf {
+    class rstringbuf : public std::basic_stringbuf<char_type, traits_type, allocator_type> {
     public:
-        char *eback() { return std::streambuf::eback(); }
+        char *eback() const { return std::streambuf::eback(); }
+        char *pptr() const { return std::streambuf::pptr(); }
     };
-    rstringbuf rsbuf_;
+    rstringbuf rstringbuf_;
 public:
     ostringstream() {
-        std::basic_ostream<char>::rdbuf(&rsbuf_);
+        std::basic_ostream<char>::rdbuf(&rstringbuf_);
     }
-    size_t size() {
-        return tellp();
+    std::string_view view() const {
+        char *p = rstringbuf_.eback();
+        size_t size = rstringbuf_.pptr() - p;
+        return std::string_view(p, size);
     }
-    const char *c_str() {
-        return rsbuf_.eback();
+    std::string str() const {
+        return rstringbuf_.str();
     }
 };
 
+
 // Remove items from a vector that are marked for deletion.
 //
 template<class T>