双指针赋值中的分段错误

Question

我已经声明了这样的双指针

UInt8  **contentKeyCtx;

此变量作为参数发送到函数内部函数中有局部变量

 UInt8    *localckc     = NULL;
 localckc = calloc(1, localckcSize);

然后分配了一些值数组 localckc

当我尝试这样做

 *contentKeyCtx = localckc;

我得到了分段错误

我做错了什么？主功能

int main (int argc, char *argv[])
{
    OSStatus result; // SInt32


    UInt8  *inBuff, *outBuff;
    UInt32 inBuffSize, outBuffSize;
    UInt8  **contentKeyCtx = calloc(1, sizeof(UInt8**));
    UInt32  *contentKeyCtxSize;
    FILE   *fp;


    const UInt8 *assetId = {0x1b, 0xf7, 0xf5, 0x3f, 0x5d, 0x5d, 0x5a, 0x1f};// what is this?



    inBuff=calloc(1,INBUFFSIZE);
    outBuff=calloc(1,OUTBUFFSIZE);


    inBuffSize = fread(inBuff, sizeof(UInt8), INBUFFSIZE, fp);

    fclose(fp);


    // IK we have some data. Now what?
    result = SKDServerGenCKC(inBuff, inBuffSize, assetId, contentKeyCtx, contentKeyCtxSize);


    free(inBuff);
    free(outBuff);
    printf("Result is  %d\n", result );
    return 0;
}

实际功能实施

    OSStatus SKDServerGenCKC(
        const UInt8   *serverPlaybackCtx,
        UInt32         serverPlaybackCtxSize,
        const UInt8   *assetId,
        UInt8        **contentKeyCtx,
        UInt32        *contentKeyCtxSize)
{

    UInt8    *localckc     = NULL;
    UInt32    localckcSize = 0;
    PS_RequireAction(ckcContainer      != NULL, return kDRMSKDServerParamErr;)
    PS_RequireAction(contentKeyCtx     != NULL, return kDRMSKDServerParamErr;)
    PS_RequireAction(contentKeyCtxSize != NULL, return kDRMSKDServerParamErr;) 
    ...
     localckc = calloc(1, localckcSize);
     status = SKDServerWriteBytes(
                &ckcContainer->parser.currentOffset, PS_AES128_IV_SZ, 
                ckcContainer->aesKeyIV, localckcSize, localckc);


    ...
    *contentKeyCtx = localckc;


}

Answer 1

您现在提供的功能实现与您对问题的原始描述有很大不同.现在很清楚,涉及的指针contentKeyCtx是函数参数,而不是本地或文件范围变量,代码显示它被用于将函数计算的指针传递回函数的调用者.

在这种情况下,函数调用的相应实际参数应该是一个适当类型的变量的地址,函数将在其中存储生成的指针值,如下所示:

UInt8        *contentKeyCtx;
UInt32       contentKeyCtxSize = 0;
OSStatus     status;

status = SKDServerGenCKC(..., &contentKeyCtx, &contentKeyCtxSize);

类似适用于最后一个参数,如图所示; 它显然用于返回返回指针所指向的空间的大小.