c - 结构体的全局数组，在程序中声明大小并全局使用而无需传递？

Question

仅供引用，我正在制作一个缓存模拟器作为 C 项目。我需要声明一个结构体的全局 double 组，在程序中设置这个全局结构体数组的大小，然后在稍后的项目中使用该全局数组。

这是我所拥有的内容的简化版本:

// Declare globals
int mapping = 0;
int offset = 0;
int index = 0;

char* allocation;
char* writePolicy;

struct cache {
    int validBit;
    int dirtyBit;
    unsigned int tag;
    unsigned int nextToReplace;
    };

void analyzeParameters(char* line, int lineNum) {

switch(lineNum) {
        case 1:
            mapping = atoi(line);
        case 2:
            offset = atoi(line);
        case 3:
            index = atoi(line);
        case 4:
            allocation = malloc(4);
            strcpy(allocation, line);
        case 5:
            writePolicy = malloc(4);
            strcpy(writePolicy, line);
    }

}

setupCache() {
int numSets = 1 << index;

struct cache cache[mapping][numSets];

printf("Declared cache struct with size %d ", numSets);
printf("num of ways %d\n", mapping);

// initialize bits in cache to 0

int j;
int i;

for (j = 0; j < mapping; j++) { 
    for (i = 0; i < numSets; i++) {
        cache[j][i].validBit = 0;
        cache[j][i].dirtyBit = 0;
    }
}

}

void hitChecker() {

for (d = 0; d < mapping; d++) {
    if (cache[d][index].validBit == 1) {
        if (cache[d][index].tag == tag) { 
            //found a hit

            if (type == "r") {
            // hit with a read instruction.
            rhits++;


            }
            else if (type == "w") {
            // hit with a write instruction
            whits++;

            }
        }

        else {
        // tag in cache index is not equal to tag being checked

            if (type == "r") {
            // missed with a read instruction.
            rmisses++;

            }
            else if (type == "w") {
            // missed with a write instruction
            wmisses++;

            }
        }
    }
    else {
    //cache is not valid
    printf("Cache has not been validated");
    }
}

void main(int argc, char**argv) {

analyzeParameters(passInEachLineOfFile, this works not important);

setupCache();

hitChecker();

}

这一直有效，直到我尝试利用缓存结构。我全局声明它，在 setUpCache 中设置大小，然后在另一个方法中我想使用全局声明的 double 组。有没有一种方法可以在全局范围内使用它，或者我是否必须通过方法参数传递结构？

Answer 1

要获得具有运行时确定大小的全局缓存结构，请使用:

int mapping, numsets;
struct cache **cache;

和:

void init(int nmaps, int nsets)
{
    cache=malloc(nmaps*sizeof(struct cache *));
    for (int i=0;i<nmaps;i++)
        cache[i]=malloc(nsets*sizeof(struct cache));
    mapping= nmaps;
    numsets= nsets;
}