Problem when using fopen with a hardcoded file name (data alignment problem ?)

slaroche — Wed, 08 Jan 2014 19:01:28 GMT

Hi,

here is what I am using : MQX 4.0.2.2 \ CW 10.2 \ Kinetis K60

I am trying to use the « fopen » on a SDCARD passing a hardcoded string for the filename. For some reason, It fails when I do so :

CfgFile = fopen ("a:\\config.txt", "r");

If I put the name into a ram buffer, then it works :

char FileName[16] = "a:\\config.txt";

CfgFile = fopen (FileName, "r");

I traced into the fopen function and I am not exactly sure what happen, but the loop that scans for all available devices (“ttya:”, “gpio:”, …) doesn’t break at the same place. A difference I can see between the two calls is that the one using the hardcoded string uses a pointer that is not 32 bit aligned (address is “0x1fff0569”) while the second one uses a 32 bit aligned adresss (0x1fffb47c). I am thinking that maybe this does a difference when comparing the strings.

Although I have a workaround for that problem (using a ram buffer), I would very like to know why it does that and how I can avoid it.

Thanks for any advice.

Re: Problem when using fopen with a hardcoded file name (data alignment problem ?)

DavidS — Fri, 17 Jan 2014 19:06:29 GMT

Hello,

No idea why that wouldn't work.

I did a simple test using the web_hvac example and could do the following

log_fp = fopen("c:\\hvac_log.txt","a"); //DES worked

#define LOG_FILE "c:\\hvac_log.txt"

log_fp = fopen(LOG_FILE,"a"); //DES worked

I wonder if something funky with your flash case where the string is not NULL terminated???

As an additional test after closing the file I then re-opened it using following code and it worked fine.

log_fp = fopen("c:\\hvac_log.txt","r");

if (log_fp) {

char temparray[31];

fgets((char *)&temparray[0], (int_32)30, log_fp);

}

Lastly when you step into the fopen() can you use your Variable window to see what the "tmp_ptr" is set to?

In my picture below it is shown as "c:\\hvac_log.txt"

Regards,

David

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Problem when using fopen with a hardcoded file name (data alignment problem ?)

Re: Problem when using fopen with a hardcoded file name (data alignment problem ?)