malloc无法分配内存

Question

i just don't get why malloc keeps failing with "Cannot allocate memory" in this function: (it triggers the perror and return -1)

EDIT: size_t is an unsigned type, of course it won't work when passing -1

int circularBuffer_get(circularBuffer_t *buf, size_t count, void ***retArray) { 
    size_t retVal = (count >= 0 ? count : buf->elCount);
    if (retVal == 0) return 0;

    /* ALloco l'array di ritorno */
    void **retArr = malloc(sizeof(void*) * retVal);
    if(!retArr) {perror("Allocating return value"); return -1; }
    memset(retArr, 0, sizeof(void*) * retVal);

    int i, j = 0; /* Percorro gli elementi da estrarre */
    for (i = (buf->bufCursor - retVal + buf->bufSize) % buf->bufSize; i < retVal; i = (i+1) % buf->bufSize ) {
        /* Estraggo l'elemento */
        retArr[j] = buf->buffer[i];

        /* Libero lo slot nel buffer */
        buf->buffer[i] = NULL;
        j++;
    }

    /* Aggiorno il numero di elementi nel buffer */
    buf->elCount -= retVal;

    *retArray = retArr;
    return retVal;
}

i am calling that function at the main function as:

circularBuffer_get(buf, -1, (void***)&arr);

notice that buf is allocated fine (i checked each value and pointer and the current value of buf->elCount is 1 (i checked that using a printf, too).

I don't think that's a problem with the virtual machine i'm using, either, as other programs run just fine allocating stuff...

Answer 1

size_t(-1) = 18446744073709551615

您可能刚用完内存:)

Answer 2

我使用的size_t类型是无符号的，将-1作为参数传递将导致此类错误