C++重載的時候會優先匹配非模組函數

發現當重載函數足夠多的時候,

出現可以符合非模組函數,及模組函數都可匹配的時候,

GCC好像會優先匹配非模組函數.

見下面代碼

#include <iostream>#include <vector>#include <string>#include <limits>using namespace std;int max(const int n1, const int n2){    return n1 > n2 ? n1 : n2;}float max( const float f1, const float f2){    return f1 > f2 ? f1 : f2;}string max(const string str1, const  string str2){    return str1 > str2 ? str1 : str2;}#if 0int max(const vector<int>& vec){    return *max_element(vec.begin(), vec.end());}float max(const vector<float>& vec){    return *max_element(vec.begin(), vec.end());}string max(const vector<string>& vec){    return *max_element(vec.begin(), vec.end());}int max(const int* array, int size){    int int_max = numeric_limits<int>::min();    for(int i = 0; i < size; ++i) {        int_max = max(int_max, array[i]);    }    return int_max;}float max(const float* array, int size){    float float_max = numeric_limits<float>::min();    for(int i = 0; i < size; ++i) {        float_max = max(float_max, array[i]);    }    return float_max;}string max(const string* array, int size){    return *max_element(array, array + size);}#endiftemplate <typename T>T max(const vector<T>& vec) {    cout << "invoke" <<endl;    return *max_element(vec.begin(), vec.end());}template <typename T>T max(const T* array, int size){    return *max_element(array, array + size);}int main(int argc, const char *argv[]){    cout << "test overload max" << endl;        int n1 = 3;    int n2 = 9;    float f1 = 3.14;    float f2 = 98.44;    string str1 = "s1";    string str2 = "abc";    cout << "max int (" << n1 << " " << n2 << " )" << max(n1, n2) << endl        << " max float (" << f1  << " " << f2 << " ) " <<  max(f1, f2)         << endl        << "max string ( " << str1 <<  " " << str2 << " ) " << max(str1, str2)        << endl;    int int_array[] = {33,444,5,322,124,55,3436};    vector<int> int_vec (int_array, int_array + sizeof(int_array)/ sizeof(int));    cout << " the max number of the int vector is : " << max(int_vec) << endl;    float f_array[] = {34.24, 4324.43, 9999.43, 556.34};    vector<float> f_vec (f_array, f_array + sizeof(f_array) / sizeof(float));    cout << " the max number of the float vector is : " << max(f_vec) << endl;    string str_array[] = {"boog", "gogod", "zero", "loe", "abcdasdfas",    "asfdksdljjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjj"};    vector<string> str_vec (str_array, str_array + sizeof(str_array) / sizeof(string));    cout << " the max number of the string vector is : " << max(str_vec) << endl;#if 1    cout << "the max number of the int array is :"         << max( int_array, sizeof(int_array)/ sizeof(int)) <<endl;    cout << "the max number of the flaot array is :"         << max( f_array, sizeof(f_array)/ sizeof(float)) <<endl;    cout << "the max number of the string array is :"         << max( str_array, sizeof(str_array)/ sizeof(str_array[0]))         << " sizes = " << sizeof(str_array)/ sizeof(str_array[0])               << " sizes of str_array " << sizeof(str_array )               << " sizes of str_array[0] " << sizeof(str_array[0] )        << endl;#endif    return 0;}

output 

test overload max
max int (3 9 )9
max float (3.14 98.44 ) 98.44
max string ( s1 abc ) s1
invoke
the max number of the int vector is : 3436
invoke
the max number of the float vector is : 9999.43
invoke
the max number of the string vector is : zero
the max number of the int array is :3436
the max number of the flaot array is :9999.43
the max number of the string array is :zero sizes = 6 sizes of str_array 24 sizes of str_array[0] 4

 

 

如果把#if 0 開啟,,那麼就不會出現invoke證明調用的是非模組函數