From: Denis Efremov
> Sent: 01 October 2019 16:13
...
> Just found an official documentation to this issue:
> https://gcc.gnu.org/gcc-4.9/porting_to.html
> "Null pointer checks may be optimized away more aggressively
> ...
> The pointers passed to memmove (and similar functions in <string.h>) must be
> non-null
> even when nbytes==0, so GCC can use that information to remove the check
> after the
> memmove call. Calling copy(p, NULL, 0) can therefore deference a null pointer
> and crash."
Right, so just don't code a NULL pointer test after a memcpy() call.
There is no need to avoid the call itself.
> But again, I would say that the bug in this code is because the if condition
> was copy-pasted
> and it should be inverted.
Oh, the code is question is just stupidly bad.
It seemed to do:
if (a)
x;
else if (!a)
y;
else
error ("all borked")
If the whole driver is written like that it needs fixing before anyone takes a
serious look at it.
David
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