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- To: hatari-devel@xxxxxxxxxxxxxxxxxxx
- Subject: Re: [hatari-devel] Patch to fix crash saving midi preferences on Mac
- From: Thomas Huth <th.huth@xxxxxxxxx>
- Date: Sat, 28 May 2022 07:19:51 +0000
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Am Fri, 27 May 2022 23:19:34 +0100
schrieb Chris Jenkins <cdpjenkins@xxxxxxxxx>:
....
> It turns out that the code is supplying the wrong size to strncpy; it
> supplies FILENAME_MAX (which is 1024 on my Mac) whereas the length of the
> field is MAX_MIDI_PORT_NAME (256).
....
> Note that I didn't expect this to crash, given that the text that is being
> copied in this case is "Off" which isn't anywhere near 256 characters long.
You missed the "hidden feature" of the strncpy function, citing the (Linux)
man page:
"If the length of src is less than n, strncpy() writes additional null
bytes to dest to ensure that a total of n bytes are written."
That means strncpy always fills the whole destination buffer - using \0 if
the source string is not long enough.
That's one more reason to rather use strlcpy instead of strncpy in most
cases.
Thomas