Wireshark · Wireshark-dev: Re: [Wireshark-dev] Memory corruption on x86_64 / GCC 4.2.3

[Guy Harris <guy@xxxxxxxxxxxx>]

On Aug 2, 2008, at 5:26 PM, Alexey Neyman wrote:

> Small correction: the option to GCC which fixes this problem
> is "-fno-tree-vrp",

...which, from the GCC 4.3 documentation, turns off an optimization  
pass:

	-ftree-vrp
		Perform Value Range Propagation on trees. This is similar to the  
constant propagation pass, but instead of values, ranges of values are  
propagated. This allows the optimizers to remove unnecessary range  
checks like array bound checks and null pointer checks. This is  
enabled by default at -O2 and higher. Null pointer check elimination  
is only done if -fdelete-null-pointer-checks is enabled.

so, all other things, I'd prefer not to turn that one off.

The documentation's discussion of -fstring-overflow mentions -fwrapv:

	-fwrapv
		This option instructs the compiler to assume that signed arithmetic  
overflow of addition, subtraction and multiplication wraps around  
using twos-complement representation. This flag enables some  
optimizations and disables others. This option is enabled by default  
for the Java front-end, as required by the Java language specification.

We only run on two's-complement platforms, as far as I know (no Univac  
mainframes run Wireshark, as far as I know), so, unless signed  
arithmetic overflow causes a trap, addition and subtraction presumably  
wrap around.  Does turning that option on fix this problem?