8293251: Use stringStream::base() instead of as_string() when applicable

src/hotspot/cpu/x86/upcallLinker_x86_64.cpp

@@ -377,7 +377,7 @@ address UpcallLinker::make_upcall_stub(jobject receiver, Method* entry,
 #ifndef PRODUCT
   stringStream ss;
   ss.print("upcall_stub_%s", entry->signature()->as_C_string());
-  const char* name = _masm->code_string(ss.base());
+  const char* name = _masm->code_string(ss.internal_string());
 #else // PRODUCT
   const char* name = "upcall_stub";
 #endif // PRODUCT

src/hotspot/share/c1/c1_GraphBuilder.cpp

@@ -140,7 +140,7 @@ BlockListBuilder::BlockListBuilder(Compilation* compilation, IRScope* scope, int
     stringStream title;
     title.print("BlockListBuilder ");
     scope->method()->print_name(&title);
-    CFGPrinter::print_cfg(_bci2block, title.base(), false, false);
+    CFGPrinter::print_cfg(_bci2block, title.internal_string(), false, false);
   }
 #endif
 }

src/hotspot/share/c1/c1_Instruction.cpp

@@ -975,7 +975,7 @@ Assert::Assert(Value x, Condition cond, bool unordered_is_true, Value y) : Instr
   ip2.print_instr(y);
 
   stringStream ss;
-  ss.print("Assertion %s %s %s in method %s", strStream1.base(), ip2.cond_name(cond), strStream2.base(), strStream.base());
+  ss.print("Assertion %s %s %s in method %s", strStream1.internal_string(), ip2.cond_name(cond), strStream2.internal_string(), strStream.internal_string());
 
   _message = ss.as_string();
 }

src/hotspot/share/c1/c1_LIRAssembler.cpp

@@ -147,7 +147,7 @@ void LIR_Assembler::emit_stubs(CodeStubList* stub_list) {
       stringStream st;
       s->print_name(&st);
       st.print(" slow case");
-      _masm->block_comment(st.base());
+      _masm->block_comment(st.internal_string());
     }
 #endif
     s->emit_code(this);
@@ -262,7 +262,7 @@ void LIR_Assembler::emit_block(BlockBegin* block) {
   if (CommentedAssembly) {
     stringStream st;
     st.print_cr(" block B%d [%d, %d]", block->block_id(), block->bci(), block->end()->printable_bci());
-    _masm->block_comment(st.base());
+    _masm->block_comment(st.internal_string());
   }
 #endif
 
@@ -292,7 +292,7 @@ void LIR_Assembler::emit_lir_list(LIR_List* list) {
           (op->code() == lir_leal && op->as_Op1()->patch_code() != lir_patch_none)) {
         stringStream st;
         op->print_on(&st);
-        _masm->block_comment(st.base());
+        _masm->block_comment(st.internal_string());
       }
     }
     if (PrintLIRWithAssembly) {

src/hotspot/share/c1/c1_Runtime1.cpp

@@ -559,7 +559,7 @@ JRT_ENTRY_NO_ASYNC(static address, exception_handler_for_pc_helper(JavaThread* c
     tempst.print("C1 compiled method <%s>\n"
                  " at PC" INTPTR_FORMAT " for thread " INTPTR_FORMAT,
                  nm->method()->print_value_string(), p2i(pc), p2i(current));
-    Exceptions::log_exception(exception, tempst.base());
+    Exceptions::log_exception(exception, tempst.internal_string());
   }
   // for AbortVMOnException flag
   Exceptions::debug_check_abort(exception);
@@ -1463,7 +1463,7 @@ JRT_ENTRY(void, Runtime1::predicate_failed_trap(JavaThread* current))
     Method* inlinee = vfst.method();
     inlinee->print_short_name(&ss1);
     m->print_short_name(&ss2);
-    tty->print_cr("Predicate failed trap in method %s at bci %d inlined in %s at pc " INTPTR_FORMAT, ss1.base(), vfst.bci(), ss2.base(), p2i(caller_frame.pc()));
+    tty->print_cr("Predicate failed trap in method %s at bci %d inlined in %s at pc " INTPTR_FORMAT, ss1.internal_string(), vfst.bci(), ss2.internal_string(), p2i(caller_frame.pc()));
   }
 
 

src/hotspot/share/classfile/classLoaderDataGraph.cpp

@@ -442,7 +442,7 @@ void ClassLoaderDataGraph::print_table_statistics(outputStream* st) {
     ResourceMark rm; // loader_name_and_id
     stringStream tempst;
     tempst.print("System Dictionary for %s class loader", cld->loader_name_and_id());
-    cld->dictionary()->print_table_statistics(st, tempst.base());
+    cld->dictionary()->print_table_statistics(st, tempst.internal_string());
   }
 }
 

src/hotspot/share/code/codeCache.cpp

@@ -1506,7 +1506,7 @@ void CodeCache::report_codemem_full(CodeBlobType code_blob_type, bool print) {
     }
     {
       ttyLocker ttyl;
-      tty->print("%s", s.base());
+      tty->print("%s", s.internal_string());
     }
 
     if (full_count == 1) {

src/hotspot/share/compiler/compileBroker.cpp

@@ -552,7 +552,7 @@ void CompileQueue::print_tty() {
   print(&ss);
   {
     ttyLocker ttyl;
-    tty->print("%s", ss.base());
+    tty->print("%s", ss.internal_string());
   }
 }
 
@@ -2029,7 +2029,7 @@ static void codecache_print(bool detailed)
     CodeCache::print_summary(&s, detailed);
   }
   ttyLocker ttyl;
-  tty->print("%s", s.base());
+  tty->print("%s", s.internal_string());
 }
 
 // wrapper for CodeCache::print_summary() using outputStream
@@ -2355,7 +2355,7 @@ void CompileBroker::handle_full_code_cache(CodeBlobType code_blob_type) {
       // Lock to prevent tearing
       ttyLocker ttyl;
       xtty->begin_elem("code_cache_full");
-      xtty->print("%s", s.base());
+      xtty->print("%s", s.internal_string());
       xtty->stamp();
       xtty->end_elem();
     }

src/hotspot/share/gc/shenandoah/shenandoahAsserts.cpp

@@ -48,7 +48,7 @@ void print_raw_memory(ShenandoahMessageBuffer &msg, void* loc) {
     stringStream ss;
     os::print_hex_dump(&ss, start, end, 4);
     msg.append("\n");
-    msg.append("Raw heap memory:\n%s", ss.base());
+    msg.append("Raw heap memory:\n%s", ss.internal_string());
   }
 }
 
@@ -71,8 +71,8 @@ void ShenandoahAsserts::print_obj(ShenandoahMessageBuffer& msg, oop obj) {
   msg.append("    %3s marked strong\n",              ctx->is_marked_strong(obj) ? "" : "not");
   msg.append("    %3s marked weak\n",                ctx->is_marked_weak(obj) ? "" : "not");
   msg.append("    %3s in collection set\n",          heap->in_collection_set(obj) ? "" : "not");
-  msg.append("  mark:%s\n", mw_ss.base());
-  msg.append("  region: %s", ss.base());
+  msg.append("  mark:%s\n", mw_ss.internal_string());
+  msg.append("  region: %s", ss.internal_string());
 }
 
 void ShenandoahAsserts::print_non_obj(ShenandoahMessageBuffer& msg, void* loc) {
@@ -84,12 +84,12 @@ void ShenandoahAsserts::print_non_obj(ShenandoahMessageBuffer& msg, void* loc) {
     r->print_on(&ss);
 
     msg.append("    %3s in collection set\n",    heap->in_collection_set_loc(loc) ? "" : "not");
-    msg.append("  region: %s", ss.base());
+    msg.append("  region: %s", ss.internal_string());
   } else {
     msg.append("  outside of Java heap\n");
     stringStream ss;
     os::print_location(&ss, (intptr_t) loc, false);
-    msg.append("  %s", ss.base());
+    msg.append("  %s", ss.internal_string());
   }
 }
 
@@ -101,7 +101,7 @@ void ShenandoahAsserts::print_obj_safe(ShenandoahMessageBuffer& msg, void* loc)
     if (r != NULL) {
       stringStream ss;
       r->print_on(&ss);
-      msg.append("  region: %s", ss.base());
+      msg.append("  region: %s", ss.internal_string());
       print_raw_memory(msg, loc);
     }
   }

src/hotspot/share/gc/shenandoah/shenandoahHeapRegion.cpp

@@ -80,7 +80,7 @@ void ShenandoahHeapRegion::report_illegal_transition(const char *method) {
   stringStream ss;
   ss.print("Illegal region state transition from \"%s\", at %s\n  ", region_state_to_string(_state), method);
   print_on(&ss);
-  fatal("%s", ss.base());
+  fatal("%s", ss.internal_string());
 }
 
 void ShenandoahHeapRegion::make_regular_allocation() {

src/hotspot/share/gc/shenandoah/shenandoahNMethod.cpp

@@ -250,7 +250,7 @@ void ShenandoahNMethod::assert_same_oops(bool allow_dead) {
       debug_stream.print_cr("-> " PTR_FORMAT, p2i(check.at(i)));
     }
     fatal("Must match #detected: %d, #recorded: %d, #total: %d, begin: " PTR_FORMAT ", end: " PTR_FORMAT "\n%s",
-          oops->length(), _oops_count, count, p2i(nm()->oops_begin()), p2i(nm()->oops_end()), debug_stream.base());
+          oops->length(), _oops_count, count, p2i(nm()->oops_begin()), p2i(nm()->oops_end()), debug_stream.internal_string());
   }
 }
 #endif

src/hotspot/share/gc/shenandoah/shenandoahVerifier.cpp

@@ -768,7 +768,7 @@ void ShenandoahVerifier::verify_at_safepoint(const char *label,
         stringStream ss;
         r->print_on(&ss);
         fatal("%s: Live data should match: region-live = " SIZE_FORMAT ", verifier-live = " UINT32_FORMAT "\n%s",
-              label, reg_live, verf_live, ss.base());
+              label, reg_live, verf_live, ss.internal_string());
       }
     }
   }

src/hotspot/share/jvmci/jvmciCompilerToVM.cpp

@@ -963,7 +963,7 @@ C2V_VMENTRY_0(jint, installCode0, (JNIEnv *env, jobject,
       CodeCache::print_summary(&s, false);
     }
     ttyLocker ttyl;
-    tty->print_raw_cr(s.base());
+    tty->print_raw_cr(s.internal_string());
   }
 
   if (result != JVMCI::ok) {

src/hotspot/share/opto/castnode.cpp

@@ -248,7 +248,7 @@ const Type* CastIINode::Value(PhaseGVN* phase) const {
             } else {
               stringStream ss;
               test.dump_on(&ss);
-              fatal("unexpected comparison %s", ss.base());
+              fatal("unexpected comparison %s", ss.internal_string());
             }
             int lo_int = (int)lo_long;
             int hi_int = (int)hi_long;

src/hotspot/share/opto/compile.cpp

@@ -4499,7 +4499,7 @@ void Compile::process_print_inlining() {
     assert(_print_inlining_list != NULL, "process_print_inlining should be called only once.");
     for (int i = 0; i < _print_inlining_list->length(); i++) {
       PrintInliningBuffer* pib = _print_inlining_list->at(i);
-      ss.print("%s", pib->ss()->base());
+      ss.print("%s", pib->ss()->internal_string());
       delete pib;
       DEBUG_ONLY(_print_inlining_list->at_put(i, NULL));
     }
@@ -4510,7 +4510,7 @@ void Compile::process_print_inlining() {
     print_inlining_stream_free();
     size_t end = ss.size();
     _print_inlining_output = NEW_ARENA_ARRAY(comp_arena(), char, end+1);
-    strncpy(_print_inlining_output, ss.base(), end+1);
+    strncpy(_print_inlining_output, ss.internal_string(), end+1);
     _print_inlining_output[end] = 0;
   }
 }

src/hotspot/share/opto/compile.hpp

@@ -491,7 +491,7 @@ class Compile : public Phase {
   void print_inlining(ciMethod* method, int inline_level, int bci, const char* msg = NULL) {
     stringStream ss;
     CompileTask::print_inlining_inner(&ss, method, inline_level, bci, msg);
-    print_inlining_stream()->print("%s", ss.base());
+    print_inlining_stream()->print("%s", ss.internal_string());
   }
 
 #ifndef PRODUCT

src/hotspot/share/opto/doCall.cpp

@@ -62,7 +62,7 @@ void trace_type_profile(Compile* C, ciMethod *method, int depth, int bci, ciMeth
     out->print(" \\-> TypeProfile (%d/%d counts) = ", receiver_count, site_count);
     stringStream ss;
     prof_klass->name()->print_symbol_on(&ss);
-    out->print("%s", ss.base());
+    out->print("%s", ss.internal_string());
     out->cr();
   }
 }

src/hotspot/share/opto/idealGraphPrinter.cpp

@@ -201,7 +201,7 @@ void IdealGraphPrinter::end_head() {
 void IdealGraphPrinter::print_attr(const char *name, intptr_t val) {
   stringStream stream;
   stream.print(INTX_FORMAT, val);
-  print_attr(name, stream.base());
+  print_attr(name, stream.internal_string());
 }
 
 void IdealGraphPrinter::print_attr(const char *name, const char *val) {
@@ -225,7 +225,7 @@ void IdealGraphPrinter::text(const char *s) {
 void IdealGraphPrinter::print_prop(const char *name, int val) {
   stringStream stream;
   stream.print("%d", val);
-  print_prop(name, stream.base());
+  print_prop(name, stream.internal_string());
 }
 
 void IdealGraphPrinter::print_prop(const char *name, const char *val) {
@@ -246,7 +246,7 @@ void IdealGraphPrinter::print_method(ciMethod *method, int bci, InlineTree *tree
   method->print_short_name(&shortStr);
 
   print_attr(METHOD_NAME_PROPERTY, str.base());
-  print_attr(METHOD_SHORT_NAME_PROPERTY, shortStr.base());
+  print_attr(METHOD_SHORT_NAME_PROPERTY, shortStr.internal_string());
   print_attr(METHOD_BCI_PROPERTY, bci);
 
   end_head();
@@ -305,7 +305,7 @@ void IdealGraphPrinter::begin_method() {
   // Add method name
   stringStream strStream;
   method->print_name(&strStream);
-  print_prop(METHOD_NAME_PROPERTY, strStream.base());
+  print_prop(METHOD_NAME_PROPERTY, strStream.internal_string());
 
   if (method->flags().is_public()) {
     print_prop(METHOD_IS_PUBLIC_PROPERTY, TRUE_VALUE);
@@ -318,7 +318,7 @@ void IdealGraphPrinter::begin_method() {
   if (C->is_osr_compilation()) {
       stringStream ss;
       ss.print("bci: %d, line: %d", C->entry_bci(), method->line_number_from_bci(C->entry_bci()));
-      print_prop(COMPILATION_OSR_PROPERTY, ss.base());
+      print_prop(COMPILATION_OSR_PROPERTY, ss.internal_string());
   }
 
   print_prop(COMPILATION_ID_PROPERTY, C->compile_id());
@@ -601,7 +601,7 @@ void IdealGraphPrinter::visit_node(Node *n, bool edges, VectorSet* temp_set) {
         bciStream.print("%d ", caller->bci());
         caller = caller->caller();
       }
-      print_prop("bci", bciStream.base());
+      print_prop("bci", bciStream.internal_string());
       if (last != NULL && last->has_linenumber_table() && last_bci >= 0) {
         print_prop("line", last->line_number_from_bci(last_bci));
       }
@@ -611,7 +611,7 @@ void IdealGraphPrinter::visit_node(Node *n, bool edges, VectorSet* temp_set) {
     if (node->debug_orig() != NULL) {
       stringStream dorigStream;
       node->dump_orig(&dorigStream, false);
-      print_prop("debug_orig", dorigStream.base());
+      print_prop("debug_orig", dorigStream.internal_string());
     }
 #endif
 

src/hotspot/share/opto/library_call.cpp

@@ -154,7 +154,7 @@ JVMState* LibraryIntrinsic::generate(JVMState* jvms) {
     msg_stream.print("Did not generate intrinsic %s%s at bci:%d in",
                      vmIntrinsics::name_at(intrinsic_id()),
                      is_virtual() ? " (virtual)" : "", bci);
-    const char *msg = msg_stream.base();
+    const char *msg = msg_stream.internal_string();
     log_debug(jit, inlining)("%s", msg);
     if (C->print_intrinsics() || C->print_inlining()) {
       tty->print("%s", msg);
@@ -215,7 +215,7 @@ Node* LibraryIntrinsic::generate_predicate(JVMState* jvms, int predicate) {
     msg_stream.print("Did not generate intrinsic %s%s at bci:%d in",
                      vmIntrinsics::name_at(intrinsic_id()),
                      is_virtual() ? " (virtual)" : "", bci);
-    const char *msg = msg_stream.base();
+    const char *msg = msg_stream.internal_string();
     log_debug(jit, inlining)("%s", msg);
     if (C->print_intrinsics() || C->print_inlining()) {
       C->print_inlining_stream()->print("%s", msg);

src/hotspot/share/opto/output.cpp

@@ -1472,7 +1472,7 @@ void PhaseOutput::fill_buffer(CodeBuffer* cb, uint* blk_starts) {
     if (!block->is_connector()) {
       stringStream st;
       block->dump_head(C->cfg(), &st);
-      MacroAssembler(cb).block_comment(st.base());
+      MacroAssembler(cb).block_comment(st.internal_string());
     }
     jmp_target[i] = 0;
     jmp_offset[i] = 0;
@@ -1925,13 +1925,13 @@ void PhaseOutput::fill_buffer(CodeBuffer* cb, uint* blk_starts) {
       }
       if (C->method() != NULL) {
         tty->print_cr("----------------------- MetaData before Compile_id = %d ------------------------", C->compile_id());
-        tty->print_raw(method_metadata_str.base());
+        tty->print_raw(method_metadata_str.internal_string());
       } else if (C->stub_name() != NULL) {
         tty->print_cr("----------------------------- RuntimeStub %s -------------------------------", C->stub_name());
       }
       tty->cr();
       tty->print_cr("------------------------ OptoAssembly for Compile_id = %d -----------------------", C->compile_id());
-      tty->print_raw(dump_asm_str.base());
+      tty->print_raw(dump_asm_str.internal_string());
       tty->print_cr("--------------------------------------------------------------------------------");
       if (xtty != NULL) {
         xtty->tail("opto_assembly");

src/hotspot/share/opto/runtime.cpp

@@ -1720,9 +1720,9 @@ NamedCounter* OptoRuntime::new_named_counter(JVMState* youngest_jvms, NamedCount
   }
   NamedCounter* c;
   if (tag == NamedCounter::RTMLockingCounter) {
-    c = new RTMLockingNamedCounter(st.base());
+    c = new RTMLockingNamedCounter(st.internal_string());
   } else {
-    c = new NamedCounter(st.base(), tag);
+    c = new NamedCounter(st.internal_string(), tag);
   }
 
   // atomically add the new counter to the head of the list.  We only
@@ -1756,5 +1756,5 @@ static void trace_exception(outputStream* st, oop exception_oop, address excepti
   tempst.print(" at " INTPTR_FORMAT,  p2i(exception_pc));
   tempst.print("]");
 
-  st->print_raw_cr(tempst.base());
+  st->print_raw_cr(tempst.internal_string());
 }

src/hotspot/share/prims/vectorSupport.cpp

@@ -182,7 +182,7 @@ Handle VectorSupport::allocate_vector_payload(InstanceKlass* ik, frame* fr, Regi
   } else if (!payload->is_object() && !payload->is_constant_oop()) {
     stringStream ss;
     payload->print_on(&ss);
-    assert(false, "expected 'object' value for scalar-replaced boxed vector but got: %s", ss.base());
+    assert(false, "expected 'object' value for scalar-replaced boxed vector but got: %s", ss.internal_string());
 #endif
   }
   return Handle(THREAD, nullptr);

src/hotspot/share/prims/whitebox.cpp

@@ -2462,7 +2462,7 @@ WB_ENTRY(void, WB_VerifyFrames(JNIEnv* env, jobject wb, jboolean log, jboolean u
   }
   if (log) {
     tty->print_cr("[WhiteBox::VerifyFrames] Walking Frames");
-    tty->print_raw(st.base());
+    tty->print_raw(st.internal_string());
     tty->print_cr("[WhiteBox::VerifyFrames] Done");
   }
 WB_END

src/hotspot/share/runtime/deoptimization.cpp

@@ -161,7 +161,7 @@ void Deoptimization::UnrollBlock::print() {
     st.print(INTX_FORMAT " ", frame_sizes()[index]);
   }
   st.cr();
-  tty->print_raw(st.base());
+  tty->print_raw(st.internal_string());
 }
 
 
@@ -214,7 +214,7 @@ static void print_objects(JavaThread* deoptee_thread,
       k->oop_print_on(obj(), &st);
     }
   }
-  tty->print_raw(st.base());
+  tty->print_raw(st.internal_string());
 }
 
 static bool rematerialize_objects(JavaThread* thread, int exec_mode, CompiledMethod* compiled_method,
@@ -321,7 +321,7 @@ static void restore_eliminated_locks(JavaThread* thread, GrowableArray<compiledV
             }
           }
         }
-        tty->print_raw(st.base());
+        tty->print_raw(st.internal_string());
       }
 #endif // !PRODUCT
     }
@@ -1582,7 +1582,7 @@ vframeArray* Deoptimization::create_vframeArray(JavaThread* thread, frame fr, Re
       st.print(" - %s", code_name);
       st.print_cr(" @ bci=%d ", bci);
     }
-    tty->print_raw(st.base());
+    tty->print_raw(st.internal_string());
     tty->cr();
   }
 
@@ -2063,7 +2063,7 @@ JRT_ENTRY(void, Deoptimization::uncommon_trap_inner(JavaThread* current, jint tr
           class_name->print_symbol_on(&st);
         }
         st.cr();
-        tty->print_raw(st.base());
+        tty->print_raw(st.internal_string());
       }
       if (xtty != NULL) {
         // Log the precise location of the trap.

src/hotspot/share/runtime/vframeArray.cpp

@@ -592,7 +592,7 @@ void vframeArray::unpack_to_stack(frame &unpack_frame, int exec_mode, int caller
     st.print_cr("DEOPT UNPACKING thread=" INTPTR_FORMAT " vframeArray=" INTPTR_FORMAT " mode=%d",
                 p2i(current), p2i(this), exec_mode);
     st.print_cr("   Virtual frames (outermost/oldest first):");
-    tty->print_raw(st.base());
+    tty->print_raw(st.internal_string());
   }
 
   // Do the unpacking of interpreter frames; the frame at index 0 represents the top activation, so it has no callee
@@ -630,7 +630,7 @@ void vframeArray::unpack_to_stack(frame &unpack_frame, int exec_mode, int caller
       st.print(" - %s", code_name);
       st.print(" @ bci=%d ", bci);
       st.print_cr("sp=" PTR_FORMAT, p2i(elem->iframe()->sp()));
-      tty->print_raw(st.base());
+      tty->print_raw(st.internal_string());
     }
     elem->unpack_on_stack(caller_actual_parameters,
                           callee_parameters,

src/hotspot/share/utilities/ostream.cpp

@@ -358,6 +358,7 @@ void stringStream::grow(size_t new_capacity) {
 }
 
 void stringStream::write(const char* s, size_t len) {
+  assert(_internal_string_called == false, "Modification forbidden");
   assert(_capacity >= _written + 1, "Sanity");
   if (len == 0) {
     return;
@@ -397,6 +398,7 @@ void stringStream::zero_terminate() {
 }
 
 void stringStream::reset() {
+  assert(_internal_string_called == false, "Modification forbidden");
   _written = 0; _precount = 0; _position = 0;
   _newlines = 0;
   zero_terminate();

src/hotspot/share/utilities/ostream.hpp

@@ -192,7 +192,7 @@ class ttyUnlocker: StackObj {
 // for writing to strings; buffer will expand automatically.
 // Buffer will always be zero-terminated.
 class stringStream : public outputStream {
-  // Invariant: Do not alter stringStream after calling ::base()
+  DEBUG_ONLY(bool _internal_string_called = false);
   char*  _buffer;
   size_t _written;  // Number of characters written, excluding termin. zero
   size_t _capacity;
@@ -220,8 +220,14 @@ class stringStream : public outputStream {
   // Returns internal buffer containing the accumulated string.
   // Returned buffer is only guaranteed to be valid as long as stream is not modified
   const char* base() const { return _buffer; }
+  // Return internal buffer containing the accumulated string.
+  // Ensures that further modification of stringStream leads to assertion errors.
+  const char* internal_string() NOT_DEBUG(const) {
+    DEBUG_ONLY(_internal_string_called = true);
+    return _buffer;
+  };
   void  reset();
-  // copy to a resource, or C-heap, array as requested
+  // Copy to a resource, or C-heap, array as requested
   char* as_string(bool c_heap = false) const;
 };