I am testing the example code posted on the official libtorrent website (https://www.libtorrent.org/tutorial-ref.html). I pasted the code here:
#include <libtorrent/session.hpp>
#include <libtorrent/add_torrent_params.hpp>
#include <libtorrent/torrent_handle.hpp>
#include <libtorrent/magnet_uri.hpp>
int main(int argc, char const* argv[])
{
if (argc != 2) {
fprintf(stderr, "usage: %s <magnet-url>\n");
return 1;
}
lt::session ses;
lt::add_torrent_params atp = lt::parse_magnet_uri(argv[1]);
atp.save_path = "."; // save in current dir
lt::torrent_handle h = ses.add_torrent(atp);
// ...
}
I have already installed the libtorrent:
ldconfig -v | grep libtorrent
libtorrent-rasterbar.so.9 -\> libtorrent-rasterbar.so.9.0.0
I used the following command to compile the code:
g++ main.cpp -o run -ltorrent-rasterbar -lboost_filesystem-mt
However, I got errors:
main.cpp: In function 'int main(int, const char\*\*)':
main.cpp:12:3: error: 'lt' has not been declared
lt::session ses;
I also saw another solution, but it does not resolve the issue I am facing: How to compile a libtorrent(rasterbar) code ?
Does anyone know what caused this failure?
Related
Context
I have been working with C++ for about the past 5-6 months and I'm beginning to learn gRPC. I have followed many tutorials online to get started, but I want to build a client-server communication app from scratch. Probably a bit too much, but I'm doing my best to understand how to get it all to work from the ground up rather than downloading, typing 'make', and then having a working product that I don't know how to implement into my own projects.
Goal: Create and run a simple C++ gRPC client-server communication
Versions
Using VSCode IDE.
Protoc = libprotoc 3.17.3
gRPC = 1.41.1
make = 3.81
Files
mathtest.proto
syntax = "proto3";
option java_package = "ex.grpc";
package mathtest;
// Defines the service
service MathTest {
// Function invoked to send the request
rpc sendRequest (MathRequest) returns (MathReply) {}
}
// The request message containing requested numbers
message MathRequest {
int32 a = 1;
int32 b = 2;
}
// The response message containing response
message MathReply {
int32 result = 1;
}
server.cpp
#include <string>
#include <grpcpp/grpcpp.h>
#include "mathtest.grpc.pb.h"
using grpc::Server;
using grpc::ServerBuilder;
using grpc::ServerContext;
using grpc::Status;
using mathtest::MathTest;
using mathtest::MathRequest;
using mathtest::MathReply;
class MathServiceImplementation final : public MathTest::Service {
Status sendRequest(
ServerContext* context,
const MathRequest* request,
MathReply* reply
) override {
int a = request->a();
int b = request->b();
reply->set_result(a * b);
return Status::OK;
}
};
void Run() {
std::string address("0.0.0.0:5000");
MathServiceImplementation service;
ServerBuilder builder;
builder.AddListeningPort(address, grpc::InsecureServerCredentials());
builder.RegisterService(&service);
std::unique_ptr<Server> server(builder.BuildAndStart());
std::cout << "Server listening on port: " << address << std::endl;
server->Wait();
}
int main(int argc, char** argv) {
Run();
return 0;
}
client.cpp
#include <string>
#include <grpcpp/grpcpp.h>
#include "mathtest.grpc.pb.h"
using grpc::Channel;
using grpc::ClientContext;
using grpc::Status;
using mathtest::MathTest;
using mathtest::MathRequest;
using mathtest::MathReply;
class MathTestClient {
public:
MathTestClient(std::shared_ptr<Channel> channel) : stub_(MathTest::NewStub(channel)) {}
int sendRequest(int a, int b) {
MathRequest request;
request.set_a(a);
request.set_b(b);
MathReply reply;
ClientContext context;
Status status = stub_->sendRequest(&context, request, &reply);
if(status.ok()){
return reply.result();
} else {
std::cout << status.error_code() << ": " << status.error_message() << std::endl;
return -1;
}
}
private:
std::unique_ptr<MathTest::Stub> stub_;
};
void Run() {
std::string address("0.0.0.0:5000");
MathTestClient client(
grpc::CreateChannel(
address,
grpc::InsecureChannelCredentials()
)
);
int response;
int a = 5;
int b = 10;
response = client.sendRequest(a, b);
std::cout << "Answer received: " << a << " * " << b << " = " << response << std::endl;
}
int main(int argc, char* argv[]){
Run();
return 0;
}
Steps taken for compilation
Use mathtest.proto to create the necessary files via 'protoc' (or protobuf) by executing these: protoc --grpc_out=. --plugin=protoc-gen-grpc=/opt/homebrew/bin/grpc_cpp_plugin mathtest.proto & protoc --cpp_out=. mathtest.proto
This creates the following files:
mathtest.pb.h
mathtest.pb.cc
mathtest.grpc.pb.h
mathtest.grpc.pb.cc
Compile client.cpp & server.cpp files to create executable binaries using these commands: g++ -std=c++17 client.cpp mathtest.pb.cc mathtest.grpc.pb.cc -o client 'pkg-config --libs protobuf grpc++' (NOTE: in this post, I use a single quote in the command line, but in the actual command I use a backtick; just wanted to make that clear)
Errors
As you may notice, I can't get to compiling the server because I can't get past the client compilation first. After executing the above command in step 2 of compilation, this is my output:
g++ -std=c++17 client.cpp mathtest.pb.cc mathtest.grpc.pb.cc -o client `pkg-config --libs protobuf grpc++`
client.cpp:4:10: fatal error: 'grpcpp/grpcpp.h' file not found
#include <grpcpp/grpcpp.h>
^~~~~~~~~~~~~~~~~
1 error generated.
In file included from mathtest.pb.cc:4:
./mathtest.pb.h:10:10: fatal error: 'google/protobuf/port_def.inc' file not found
#include <google/protobuf/port_def.inc>
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.
In file included from mathtest.grpc.pb.cc:5:
./mathtest.pb.h:10:10: fatal error: 'google/protobuf/port_def.inc' file not found
#include <google/protobuf/port_def.inc>
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.
make: *** [client] Error 1
Here's my real confusion...
C++ intellisense has no issues finding these files. My $PATH variables point to these folders, and my VS Code include path also point to these folders. I'm unsure where I am going wrong here...
echo $PATH returns this:
/opt/homebrew/bin:/opt/homebrew/sbin:/opt/homebrew/include:/opt/homebrew/Cellar:/opt/homebrew/opt/libtool/libexec/gnubin:/usr/bin:/bin:/usr/sbin:/sbin:/Users/tzeller/.local/bin
The folders in question ('google' & 'grcpp') live within /opt/homebrew/include and they hold the necessary files as well...
What am I missing??
Change your compile command to
g++ -std=c++17 client.cpp mathtest.pb.cc mathtest.grpc.pb.cc -o client `pkg-config --libs --cflags protobuf grpc++`
The --cflags bit asks pkg-config to spit out the necessary parameters for setting the header search path (on my system -I/opt/homebrew/Cellar/grpc/1.41.1/include and others)
I would need some help with using ngspice as a library in a webassembly (wasm) project.
I installed emsdk and newest version of emcc (1.39.20) and downloaded the source of ngspice version 32.
To my greatest surprise, I was able to compile ngspice to wasm target by following this guide:
emconfigure ./configure --with-ngshared --disable-debug
emmake make
(I had to patch configure a little to pass the checks by adding .out.js a.out.wasm to this line:)
# The possible output files:
ac_files="a.out a.out.js a.out.wasm conftest.exe conftest a.exe a_out.exe b.out conftest.*"
This produced a libngspice.so.0.0.0 file that I tried to link to from C++ code. However that failed with duplicate symbol: main. So it seemed that libngspice.so.0.0.0 contained a main function, that shouldn't have been there if I understand the purpose of the --with-ngshared of the configure script correctly.
So I manually removed the main function from main.c of ngspice and recomplied using the above method. This time I could successfully complie my own project, linking to ngspice. However when I call ngSpice_Init, I recieve the following runtime errors:
stderr Note: can't find init file.
exception thrown: RuntimeError: unreachable executed,#http://localhost:8001/sim.js line 1802 > WebAssembly.instantiate:wasm-function[67]:0x24e9
#http://localhost:8001/sim.js line 1802 > WebAssembly.instantiate:wasm-function[88]:0x423b
...
Minimal reproducible steps:
compile ngspice as above
compile the code below using em++ -o sim.html sim.cpp lib/libngspice.so
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "sharedspice.h"
using namespace std;
int recieve_char(char * str, int id, void* p){
printf("recieved %s\n", str);
}
int recieve_stat(char* status, int id, void* p){
printf("status: %s\n", status);
}
int ngexit(int status, bool unload, bool exit, int id, void* p){
printf("exit: %d\n", status);
}
int recieve_data(vecvaluesall* data, int numstructs, int id, void* p){
printf("data recieved: %f\n", data->vecsa[0]->creal);
}
int recieve_init_data(vecinfoall* data, int id, void* p){
printf("init data recieved from: %d\n", id);
}
int ngrunning(bool running, int id, void* p){
if(running){
printf("ng is running\n");
}else{
printf("ng is not running\n");
}
}
int main(){
ngSpice_Init(&recieve_char, &recieve_stat, &ngexit,
&recieve_data, &recieve_init_data, &ngrunning, (void*)NULL);
char** circarray = (char**)malloc(sizeof(char*) * 7);
circarray[0] = strdup("test array");
circarray[1] = strdup("V1 1 0 1");
circarray[2] = strdup("R1 1 2 1");
circarray[3] = strdup("C1 2 0 1 ic=0");
circarray[4] = strdup(".tran 10u 3 uic");
circarray[5] = strdup(".end");
circarray[6] = NULL;
ngSpice_Circ(circarray);
ngSpice_Command("run");
return 0;
}
So could someone please help me correctly compiling ngspice library to wasm target?
(Before someone asks, yes, I've seen this question, but it didn't help much)
I was able to compile the library and my example code after making several changes to the ngspice source. The patch and a guide on how to compile ngspice to wasm, can be found here.
(The issue leading to the error shown in my question was with the example code, not returning anything from functions that by signature should return int. This is not tolerated in wasm.)
I have installed OpenCv with Homebrew on my MacOs. I have added libopencv 4.0.1.dylib in Xcode. When I try to build, Xcode cannot find the files. Any suggestions?
I changed my path but still have problems.
Main code:
#include <iostream>
#include <opencv4/opencv2/opencv.hpp>
int main(int argc, const char * argv[]) {
// insert code here...
std::cout << "Hello, World!\n";
return 0;
}
Build settings including path:
Error messages:
I am trying to run rsync through execvp with StrictHostKeyChecking option.
This is my code:
#include <unistd.h>
int main() {
char *argv[] = {"rsync",
"remote_user#1.2.4.5:/tmp",
"/home/tmp/",
"-e 'ssh -o StrictHostKeyChecking=no'",
0};
execvp("rsync", argv);
}
I am getting this error:
rsync: -e '-o StrictHostKeyChecking=no': unknown option
rsync error: syntax or usage error (code 1) at main.c(1422) [client=3.0.6]
I have tried another way:
#include <unistd.h>
int main() {
char *argv[] = {"rsync",
"remote_user#1.2.4.5:/tmp",
"/home/tmp/",
"-e",
"'ssh -o StrictHostKeyChecking=no'",
0};
execvp("rsync", argv);
}
But now it is failing with error:
rsync: Failed to exec ssh -o StrictHostKeyChecking=no: No such file or directory (2) rsync error: error in IPC code (code 14) at pipe.c(84) [sender=3.0.6]
Why it don't understand StrictHostKeyChecking option?
rsync expects to receive the options first, followed by the hosts. You're doing it backwards: first you need to specify -e and -o.
You also shouldn't be single-quoting the -o option: that is needed when invoking it from bash, to prevent bash from interpreting the arguments and splitting them into separate argv[] entries. Think about it: when bash sees '-o StrictHostKeyChecking=no', it passes -o StrictHostKeyChecking=no as a single argv[] entry, without the single quotes (because the single quotes is your way to tell the shell that you don't want argument splitting).
Last, but not least, you should check that execvp(3) didn't fail.
So, this is what you need:
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
int main() {
char *argv[] = {
"rsync",
"-e",
"ssh -o StrictHostKeyChecking=no",
"remote_user#1.2.4.5:/tmp",
"/home/tmp/",
NULL
};
if (execvp("rsync", argv) < 0) {
perror("rsync(1) error");
exit(EXIT_FAILURE);
}
return 0;
}
After I learned the very basics of cpp i decided to push myself ahead and try SDL2 and try to make a game. I found the lazy foo's SDL tutorials. I tried to follow it but i seemed to have problems with installation. After putting in a "test" code i tried compiling it, and these messages showed up on the log:
C:\File\Location\For\My\Project\Makefile.win file not recognized: File format not recognized
C:\File\Location\For\My\Project\collect2.exe [Error] ld returned 1 exit status
I think it might be a linking error and heres my linkers:-lmingw32-lSDL2main-lSDL2
I tried deleting this Makefile.win but the same message just showed up and there isn't even a collect2.exe
I'm using the Orwell Dev-C++ using the mingw gcc 4.8.1 32bit release compiler, and heres the code:
#include <iostream>
#include <SDL2/SDL.h>
int main(int argc, char **argv){
if (SDL_Init(SDL_INIT_EVERYTHING) != 0){
std::cout << "SDL_Init Error: " << SDL_GetError() << std::endl;
return 1;
}
SDL_Quit();
return 0;
}