符号未出现在目标文件中

Question

由于某种原因，此文件中定义的符号之一未出现在目标文件中：

/**
 * || File: random.cc
 * || Project: Shatter
 * || Encoding: UTF-8
 * || Author: ********
 *
 * Copyright (C) 2016 ********** *. ****
 * All rights reserved.
 * Use by explicit written permission only.
 *
 * Changelog:
 *   - Aug 24, 2016, 07:35:22 PM --- File was created by ********
 *
 */

#include <shatter/random/random.h>

// @TODO: MOVE TO <config-build.h>
#define _M_FEATURE_ARC4RANDOM

#ifdef _M_FEATURE_ARC4RANDOM
    #define RAND_SEED (arc4random())
    #define RAND_IMPL (rand())
#else
    #include <time.h>

    #define RAND_SEED (time(NULL))
    #define RAND_IMPL (rand())
#endif

#define _M_RANDOM_SET_SEED (srand( RAND_SEED ));

namespace shatter { namespace random {
    static bool randomIsSeeded = false;

    int random(int min, int max){
        if(!randomIsSeeded){
            _M_RANDOM_SET_SEED;
            randomIsSeeded = true;
        }

        return (
            (RAND_IMPL %
                (max - min)
            ) + min
        );
    }

    int d(int num, int sides){
        int ttl = 0;
        for(int di = 0;di < num;di++)
            ttl += random(1, sides);

        return ttl;
    }

    template <class T>
        T randomFromSet(std::map<T, int> probs_keys){
            int total_prob = 0;

            /* HERE BE DRAGONS! */
            typedef typename std::map<T, int>::iterator __local__iterator;

            for(__local__iterator tprob_iter = probs_keys.begin();
                    tprob_iter != probs_keys.end();
                    ++tprob_iter) {
                total_prob += tprob_iter->last;
            }

            int target = random(0, total_prob);

            for(__local__iterator targp_iter = probs_keys.begin();
                    targp_iter != probs_keys.end();
                    ++targp_iter){
                if(target < targp_iter->last){
                    return targp_iter->first;
                }
            }
        }
} }

#undef _M_RANDOM_SET_SEED
#undef RAND_SEED
#undef RAND_IMPL

shatter/random/random.h:

#include <stdlib.h>
#include <map>

namespace shatter { namespace random {

    /**
     * min <= random(min, max) < max
     */
    int random(int min, int max);

    /**
     * num <= d(num, sides) <= (num * sides)
     */
    int d(int num, int sides);

    template <class T>
        T randomFromSet(std::map<T, int>);
} }

我用clang++ -g -std=c++11 -c编译上面的文件。出于某种原因，所有定义的符号都放入目标文件中，除了 randomFromSet().

$ nm build/random/random.o
00000000000007a0 s EH_frame0
0000000000000050 T __ZN7shatter6random1dEii
0000000000000000 T __ZN7shatter6random6randomEii
0000000000000808 b __ZN7shatter6randomL14randomIsSeededE
                 U _arc4random
                 U _rand
                 U _srand

randomFromSet() 从以下函数调用：

void Map::randomize(std::map<TileType, int> possibilities, int x, int y, int w, int h){
    this->enforceBounds(&x, &y);
    this->enforceBounds(&w, &h);

    for(int yi = y;yi < h;yi++){
        for(int xi = x;xi < w;xi++){
            int tmp_type = shatter::random::randomFromSet<TileType>(possibilities);

            this->tileMap[yi][xi]->type = (TileType) tmp_type;
        }
    }
}

另外：整体编译时：

Undefined symbols for architecture x86_64:
  "shatter::dungeon::TileType shatter::random::randomFromSet<shatter::dungeon::TileType>(std::__1::map<shatter::dungeon::TileType, int, std::__1::less<shatter::dungeon::TileType>, std::__1::allocator<std::__1::pair<shatter::dungeon::TileType const, int> > >)", referenced from:
  shatter::dungeon::Map::randomize(std::__1::map<shatter::dungeon::TileType, int, std::__1::less<shatter::dungeon::TileType>, std::__1::allocator<std::__1::pair<shatter::dungeon::TileType const, int> > >, int, int, int, int) in map.o

如果有人能告诉我 randomFromSet 没有出现在目标文件中的原因，我将不胜感激。

提前致谢。

Answer 1

该函数是一个 template 并且在它存在之前需要有一个调用者。

调用template函数。它已经需要一个实现或定义（通常在头文件中）。

见so: explicitly instantiate a function

符号未出现在目标文件中

Symbol not showing up in object file

c++

templates

object-files