CODEWITHSUNDEEP
c++shared-ptr
Philippe Hebert
Philippe Hebert

Reputation: 2028

C++ compilation error: no matching constructor for initialization

I am experiencing trouble with the compilation of my C++. Namely, I get the following obscure error from the header:

In file included from .../map.test.cpp:1:
/Library/Developer/CommandLineTools/usr/include/c++/v1/memory:2172:15: error: no matching constructor for initialization of
  'SmallWorld::Map::Graph<SmallWorld::Region>'
          __second_(_VSTD::forward<_Args2>(_VSTD::get<_I2>(__second_args))...)

The code in question is the following:

#include <memory>
#include <string>
#include <gtest/gtest.h>
#include "../../../app/Domain/Map/loader.cpp"

using std::string;

TEST(creates_a_connected_graph, small_world_map){
  using SmallWorld::Region;
  using Graph = SmallWorld::Map::Graph<Region>;
  using search_set = std::set<string>;
  using forest_map = std::unordered_map<string, std::pair<string, string>>;

  std::shared_ptr<Graph> g = SmallWorld::Map::loadMap("./map.json");
  const size_t order = g->order();
  const size_t dfs_order = SmallWorld::Map::algorithm::dfs<Region>(
    "r1",
    [](const string&, const search_set&, const forest_map&) -> bool { return true; }
  )(*g);
  ASSERT_EQ(order, dfs_order);
};

where the faulty line is most likely at the shared_ptr instantiation. The call to loadMap calls the following function:

std::shared_ptr<Map::Graph<Region>> loadMap(const string& path, const string& schema = "./map.ajv.json") {
      using Graph = SmallWorld::Map::Graph<Region>;
      using region_ptr = std::shared_ptr<Region>;
      json* map = readMap(path, schema);
      std::vector<std::pair<string, region_ptr>> regions = extractRegions(*map);
      std::vector<std::pair<string, string>> edges = extractEdges(*map);
      std::shared_ptr<Graph> pgraph = std::make_shared<Graph>(new Graph(regions, edges));
      delete map;
      return pgraph;
    };

And my only user-defined constructor of the Graph class:

Graph<E>(std::vector<std::pair<string, std::shared_ptr<E>>> nodes, std::vector<std::pair<string, string>> edges);

Setup:

I've added the verbose flag to my CMAKE_CXX_FLAGS to see if I could get something like a stack trace for the compilation error, but to no avail. This most likely is a duplicate. If you have an idea of how to solve this issue, it would be great; if you know a way to get stack-trace like errors for compilation errors, you would be my savior <3

🚀

Upvotes: 2

Views: 5726

Answers (1)

t.niese
t.niese

Reputation: 40882

Use std::make_shared<Graph> the same way you would use new Graph, as of that it has to be:

std::make_shared<Graph>(regions, edges);

The std::make_shared<Graph>(new Graph(regions, edges)); is as if you would write new Graph( new Graph(regions, edges) ).

What you may have seen and meant is std::shared_ptr<Graph>(new Graph(regions, edges));, but that's a construct you should not use.

Upvotes: 3

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