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Re: [libmicrohttpd] Strange char 0x7f added after last POST notification

From: Christian Grothoff
Subject: Re: [libmicrohttpd] Strange char 0x7f added after last POST notification
Date: Mon, 13 Apr 2020 10:59:54 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0

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!


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