[lib] fixed the bug in I/O of rrgraph. Seems that the ostream require std:string after to_string conversion

Author: tangxifan

libs/librrgraph/src/base/rr_graph_builder.cpp

@@ -255,16 +255,18 @@ void RRGraphBuilder::set_node_ptc_nums(RRNodeId node, const std::string& ptc_str
 std::string RRGraphBuilder::node_ptc_nums_to_string(RRNodeId node) const {
     std::string ret;
     if (node_ptc_nums_.empty()) {
-        ret = std::to_string(node_storage_.node_ptc_num(node));
+        return std::to_string(node_storage_.node_ptc_num(node));
 //        VTR_LOG("Node ptc single: %d -> string %s\n", node_storage_.node_ptc_num(node), ret.c_str()); 
-    } else {
-        VTR_ASSERT(size_t(node) < node_ptc_nums_.size());
-        for (size_t iptc = 0; iptc < node_ptc_nums_[node].size(); iptc++) {
-            ret += std::to_string(node_ptc_nums_[node][iptc]) + ",";
-        }
-        /* Remove the last comma */
-        ret.pop_back();
     }
+    VTR_ASSERT(size_t(node) < node_ptc_nums_.size());
+    if (node_ptc_nums_[node].empty()) {
+        return std::to_string(node_storage_.node_ptc_num(node));
+    }
+    for (size_t iptc = 0; iptc < node_ptc_nums_[node].size(); iptc++) {
+        ret += std::to_string(node_ptc_nums_[node][iptc]) + ",";
+    }
+    /* Remove the last comma */
+    ret.pop_back();
     return ret;
 }
 

libs/librrgraph/src/io/gen/rr_graph_uxsdcxx.h

@@ -4020,7 +4020,7 @@ inline void write_node(T &in, std::ostream &os, Context &context){
 		auto child_context = in.get_node_loc(context);
 		os << "<loc";
 		os << " layer=\"" << in.get_node_loc_layer(child_context) << "\"";
-		os << " ptc=\"" << in.get_node_loc_ptc(child_context) << "\"";
+		os << " ptc=\"" << std::string(in.get_node_loc_ptc(child_context)) << "\"";
 		if((bool)in.get_node_loc_side(child_context))
 			os << " side=\"" << lookup_loc_side[(int)in.get_node_loc_side(child_context)] << "\"";
 		if((bool)in.get_node_loc_twist(child_context))

libs/librrgraph/src/io/rr_graph_uxsdcxx_serializer.h

@@ -713,8 +713,7 @@ class RrGraphSerializer final : public uxsd::RrGraphBase<RrGraphContextTypes> {
     }
 
     inline const char* get_node_loc_ptc(const t_rr_node& node) final {
-        std::string ret = rr_graph_builder_->node_ptc_nums_to_string(node.id());
-        return ret.c_str();
+        return rr_graph_builder_->node_ptc_nums_to_string(node.id()).c_str();
     }
     inline int get_node_loc_layer(const t_rr_node& node) final {
         return rr_graph_->node_layer(node.id());