C ++使用C库在头文件中定义了全局变量

Question

My intention is to include the LKH TSP Algorithm, which is written in C, into my C++ project.

LKH: http://www.akira.ruc.dk/~keld/research/LKH/

Sources: http://www.akira.ruc.dk/~keld/research/LKH/LKH-2.0.7.tgz

First of all I started to write a CMakeLists.txt to create a library that does not contain the LKHmain.c.

file(GLOB_RECURSE SOURCES SRC/*.c)
file(GLOB_RECURSE HEADERS SRC/INCLUDE/*.h)

include_directories(${CMAKE_CURRENT_SOURCE_DIR}/SRC/INCLUDE)

set(LIB_SOURCES ${SOURCES})
list(REMOVE_ITEM LIB_SOURCES ${CMAKE_CURRENT_SOURCE_DIR}/SRC/LKHmain.c)

add_library(lkh
    ${LIB_SOURCES}
)
target_link_libraries(lkh m)

After that I want to implement two function that uses the library. The first one just reads a file of the TSPLib and copies the values into my own Map structure. The second one should solve a TSP Problem by using my map structure without reading any file. (The program normally could only used by reading a file so this is a wrapper part)

Now my problem: All the variables are defined in the LKH.h and used by all the implementations. So eg

LKH.h

int TraceLevel; /* Specifies the level of detail of the output
               given during the solution process.
               The value 0 signifies a minimum amount of
               output. The higher the value is the more
               information is given */
Node *FirstNode;        /* First node in the list of nodes */
int InitialTourAlgorithm;

and now they are used in the *.c classes.

GreedyTour.c

#include "LKH.h"


GainType GreedyTour()
{
    Node *From, *To, *First, *Last = 0, **Perm;
    int Count, i;
    double EntryTime = GetTime();

    if (TraceLevel >= 1) {
        if (InitialTourAlgorithm == BORUVKA)
            printff("Boruvka = ");
        else if (InitialTourAlgorithm == GREEDY)
            printff("Greedy = ");
        else if (InitialTourAlgorithm == NEAREST_NEIGHBOR)
            printff("Nearest-Neighbor = ");
        else if (InitialTourAlgorithm == QUICK_BORUVKA)
            printff("Quick-Boruvka = ");
    }
    Cost = 0;
    EdgesInFragments = 0;
    From = FirstNode;
    do {
        From->Degree = 0;
        From->Tail = From;
        From->Mark = 0;
        From->Next = From->Suc;
        From->Pred = From->Suc = 0;
    }
    while ((From = From->Next) != FirstNode);

..........
..........

In this example the variables TraceLevel, InitialTourAlgorithm and FirstNode are used as global variables .

My problem: When I include the LKH.h to my class I have a lot of side effects. After executing a method, the global variables have changed. I want to reset all of them to execute to next method without any previously set values. I wrote several test cases and the gtest methods has strange effects which is in my opinion caused by the global variables behavior.

And here my wrapper files:

lkh.h

#include "model/map.h"

namespace ttp {

    class LKHWrapper {

    public:

        MapPtr createMap(std::string);

        int *calc(MapPtr map);

    };

}

lkh.cpp

#include <fstream>
#include <limits>
#include "lkh.h"

extern "C"
{
#include "LKH.h"
#include "Genetic.h"
#include "Heap.h"
}

namespace ttp {

    MapPtr LKHWrapper::createMap(std::string pathToFile) {
        ...
        [change global variables]
        ...
        return map;

    }

    int* LKHWrapper::calc(MapPtr map) {
        ...
        [change global variables]
        ...
        return BestTour
    }

What is the easiest way to solve that problem and get a side effect free implementation of that two methods?

@Mason Watmough:

Yeah but the problem is I do not define them by myself. I have to use

  extern "C" { #include "LKH.h" #include "Genetic.h" #include "Heap.h" } 

And that defines and declares the variables (see LKH.h at the C Program)

And there is no conflict or linking error! The variables only exists once at the lkh.cpp by including the LKH.h. The library liblkh.a does also not have this variables because they are ONLY defined at the LKH.h.

Answer 1

If your global variables are defined in your header file as well as your c programs, you will need to choose one or the other. either delete the global variable definitions from the c programs and put it all in the header files, or figure out how to properly put the header file into all different c programs. Conflicting variables between the header and the program is probably what caused this.