False positive of divide sizeof pointer

[Curtis Malainey]

Hello cppcheck community,

Thanks for your wonderful tool, but I think I found an error in pointer
checking. I am getting the following output

/home/curtis/sof/sof/src/drivers/imx/sdma.c:258:21: warning:inconclusive:
Division of result of sizeof() on pointer type. [divideSizeof]

  chan->index * sizeof(*pdata->ctx) / 4,


                ^

/home/curtis/sof/sof/src/drivers/imx/sdma.c:259:7: warning:inconclusive:
Division of result of sizeof() on pointer type. [divideSizeof]

  sizeof(*pdata->ctx) / 4);


  ^

/home/curtis/sof/sof/src/drivers/imx/sdma.c:275:7: warning:inconclusive:
Division of result of sizeof() on pointer type. [divideSizeof]

  sizeof(*pdata->contexts) / 4);


  ^

/home/curtis/sof/sof/src/drivers/imx/sdma.c:291:6: warning:inconclusive:
Division of result of sizeof() on pointer type. [divideSizeof]

 sizeof(*pdata->contexts) / 4);

But when you look at the code

https://github.com/thesofproject/sof/blob/master/src/drivers/imx/sdma.c#L258

You can see that it's doing a dereference on the pointer before calling
sizeof.

Removing the double dereference to just sizeof(*ctx) by creating a pointer
variable does not silence the error either. Storing the result of the
sizeof in a variable then dividing on another line does silence the error.

Tested on latest 2.3 release.

Thanks in advance.

[CHR]

Here is a reduced snippet that still gives the warning:

struct sdma_chan {
    struct sdma_context *ctx;
};

static int sdma_upload_context(struct dma_chan_data *chan)
{
    struct sdma_chan *pdata = dma_chan_get_data(chan);

    return sdma_run_c0(
               chan->index * sizeof(*pdata->ctx) / 4,
               sizeof(*pdata->ctx) / 4);
}

[CHR]

Thanks for the report. I have created a ticket: https://trac.cppcheck.net/ticket/10179