9 May
2023
9 May
'23
8:39 a.m.
Mike Bird via tde-devels wrote:
My test.c attached to my previous email - sorry I should have chosen a
different name to avoid confusion - works with gcc-10 and clang-11 in
Debian 11.7 Bullseye.
OK, thank you!
This was the solution. The code takes care of freeing the memory, but your
example is excellent one.
Thank you
--
FCD6 3719 0FFB F1BF 38EA 4727 5348 5F1F DCFE BCB0
On Mon May 8 2023 23:18:45 deloptes via tde-devels
wrote:
There is some documentation to the code but not in this regards.
Mike Bird via tde-devels wrote:
Do you have a man page for that? The test code is not written
to handle non-terminated strings. How would it know the lengths?
%as is looking for a float so let's ignore
that.
I found out %as means do not store (strip) the terminator \0. If we switch back to %s it's looking for a string
which would be
great except no memory has been allocated for the strings.
The attached works with both gcc and clang but the important thing
to remember is NEVER NEVER NEVER use scanf or any variant thereof.
What do you mean it works with gcc? I have debian with gcc-10 and it does
following: > $ ./test
> String: interpreter usb 0x04b8
> 0x0142 /usr/lib/esci/libesci-interpreter-perfection-v330
> /usr/share/esci/esfwad.bin vendor 4b8
> product 142
> library (null)
> firmware (null)
>
> >
https://dwheeler.com/secure-programs/Secure-Programs-HOWTO/dangers-c.html
I am not the owner of this code. It was working for the past 6y and as
reported when compiled last year in Buster it works as well, but now
compiled in Bullseye is not working.
For me it is not the matter of using it or not, but a change somewhere
either in gcc (Buster was using gcc-8) or in the libraries.
Also regarding the memory allocated. You are right. It is working if I
allocate memory and use %s instead of %as.
Why, oh, why?!
Is there some kind of flag or option for the compiler?
%a currently means floating point.
%as used to be a non-standard and incompatible way of asking for
memory to be assigned for the strings but it won't work unless you
use special flags. The standards-compliant way to assign memory
while scanning is %ms.
So a simple fix would be to change %as to %ms but it's hard to get
it right - you have to free(3) the allocated memory but only if the
sscanf actually some memory. The attached test3.c shows how to do
this in this simple case.
--Mike