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 - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
