c++ - 段错误 : 11 when using dynamic 3D array parameter

Question

使用 gdb 查找段错误的来源我明白了

Program received signal SIGSEGV, Segmentation fault.
0x00000001000082bf in matchCounters (input=..., size=5, 
    valid_entries=0x100020cd0 <VALID_REGIONS>, nums=0x7fff5fbff460, 
    counters=0x100020588 <VTT for std::__1::basic_ifstream<char, std::__1::char_traits<char> >+8>) at akh70P3.cpp:524
524     cout << "counters[4][1] = " << counters[4][1] << endl;

主要()

double *** all_counters;
generateCounters(all_counters);
matchCounters(/*some more parameters here*/ all_counters[0]);

匹配计数器()

在此处访问计数器会导致段错误:11

void matchCounters(/*some more parameters here*/ double ** counters) {

    //this causes segmentation fault 11
    cout << "counters[4][1] = " << counters[4][1] << endl;
}

生成计数器()

在这里访问计数器工作得很好

void generateCounters(double *** all_counters) {
    all_counters = new double ** [2];
    //region counters
    all_counters[0] = new double * [VALID_REGIONS_SIZE];
    //move kind counters
    all_counters[1] = new double * [VALID_MOVE_TYPES_SIZE];
    for(int i = 0; i < VALID_REGIONS_SIZE; i++) {
        all_counters[0][i] = new double [CATEGORIES];
    }
    for(int i = 0; i < VALID_MOVE_TYPES_SIZE; i++) {
        all_counters[1][i] = new double [CATEGORIES];
    }
    //this works just fine! why?
    cout << "all_counters[0][4][1] = " << all_counters[0][4][1] << endl;

}

Answer 1

all_counters = new double ** [2];

all_counters参数按值传递给 generateCounters() .

这会在动态范围内分配一个新数组，并将其分配给名为“all_counters”的参数，在名为“generateCounters()”的函数中.

all_counters在你的main()完全不受影响。

与其按值传递它，不如在 generateCounters() 中声明它, return它来自函数，并将其分配给 main() 中的变量.