Makefile linking error

Question

My Makefile:

CXX = g++
CXXFLAGS = -g -Wall -std=c++14
LDFLAGS = -lboost_system -lcrypto -lssl -lcpprest -lpthread

SRC := $(shell find . -name *.cpp)
OBJ = $(SRC:%.cpp=%.o)
BIN = run

all: $(BIN)

$(BIN): $(OBJ)
    $(CXX) $(LDFLAGS)

%.o: %.cpp
    $(CXX) -c $(CXXFLAGS) $< -o $@

clean:
    find . -name *.o -delete
    rm -f $(BIN)

It scans for all files *.cpp files in all subdirectories and creates corresponding *.o files. Then it tries to link everything into a final binary, but I get the following error. I don't have any idea how to resolve this issue.

/usr/lib/gcc/x86_64-pc-linux-gnu/7.2.1/../../../../lib/Scrt1.o: In function `_start':
(.text+0x20): undefined reference to `main'

Directory structure:

Makefile
sources/
    directory1
        ...cpp
    directory2
        ...cpp
    ...
    main.cpp

main.cpp content:

#include <iostream>

#include <signal.h>

#include "application/application_launcher.hpp"

Alastriona::Application::Launcher launcher;

void shutdown(int signal);

int main(int argc, const char * argv[])
{
    struct sigaction sa;
    sa.sa_handler = &::shutdown;
    sa.sa_flags = SA_RESTART;
    sigfillset(&sa.sa_mask);

    sigaction(SIGTERM, &sa, NULL);
    sigaction(SIGQUIT, &sa, NULL);
    sigaction(SIGINT, &sa, NULL);

    launcher.loadArguments(argc, argv);
    launcher.loadConfiguration();
    launcher.startApplication();
}

void shutdown(int signal)
{
    launcher.stopApplication();
}

Answer 1

int main(int argc, const char * argv[])

Is an overload due to the constness, which is not allowed, and considered ill formed §2 by the standard. The signature you need to use is

int main(int argc, char * argv[])

Edit : Your are not using any prerequisite when trying to build the target. You should have

$(BIN): $(OBJ)
    $(CXX) $^ $(LDFLAGS)