You're using strncpy(), which does NOT add the 0-terminator at the end that printf() expects.
On 4/13/20 11:27 AM, Imóveis Nacionais wrote:
> But I am just handling arrived data when *upload_data_size > 0. Here is
> the code:
>
> else if(strcmp(method, "POST") == 0)
> {
> ST_PER_THREAD_DATA* pstThreadData = *ptr;
> if( pstThreadData == NULL)
> {
> ST_PER_THREAD_DATA * cThreadData = (ST_PER_THREAD_DATA*)
> malloc(sizeof(ST_PER_THREAD_DATA));
> cThreadData->nThreadID = nThID;
> cThreadData->strData[0]='\0';
>
> *ptr = cThreadData;
> return MHD_YES;
> }
>
> if(*upload_data_size > 0)
> {
> printf("Before strcpy (%s) (%s)
> (%d)\n",pstThreadData->strData,upload_data,*upload_data_size);
> strncpy(pstThreadData->strData,upload_data,*upload_data_size);
> printf("After strcpy (%s) (%s)
> (%d)\n",pstThreadData->strData,upload_data,*upload_data_size);
>
> *upload_data_size = 0;
> return MHD_YES;
>
> //After strcpy ({"key98"}) ({"key98"}) (9)
> }
> else
> {
> //END OF POST DATA GATHERING
> printf("In the end of post we have (%s) (%d)
> \n",pstThreadData->strData, strlen(pstThreadData->strData));
> HandleClientPost(pstThreadData->strData))
> //In the end of post we have ({"key98"}) (10)
> ...
>
> Please, is there anything wrong with the (testing) code?
>
> Thank you
>
>
>
> On Mon, Apr 13, 2020 at 10:00 AM Christian Grothoff <groth...@gnunet.org
> <mailto:groth...@gnunet.org>> wrote:
>
> On 4/13/20 2:11 AM, Imóveis Nacionais wrote:
> > Then when in the "*upload_data_size = 0" situation, using a printf
> > sometimes I can see that the thread context data has the 0x7f char
> appended
> > and of course the strlen now is one char extra. This happens
> between the
> > last post call with *upload_data_size > 0 and *upload_data_size = 0.
> >
> > Does this char has any meaning in the libmicrohttpd context?
> > Why is this char being added?
>
> You're seeing undefined behavior. When '*upload_data_size' is zero, you
> are not allowed to look into '*upload_data'. It is NEVER warranted to be
> a 0-terminated char* in the first place, and right now you're just
> reading data out of bounds. Do not rely on getting 0x7f or anything
> meaningful, in fact, expect reading more than '*upload_data_size' bytes
> from '*upload_data' to be deadly.
>
> Happy hacking!
>
> Christian
>
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