bug#79781: [BUG / Question] Potential use of uninitialized variables in copy_internal() in src/copy.c

tag 79781 notabug
close 79781
stop

Details below...

On 07/11/2025 11:10, Ray steven wrote:
> Hello Coreutils maintainers,
> 
> I found a potential issue in the `copy_internal` function in `src/copy.c`.
> 
> Issue Summary
> -------------
> In lines 1641–1642, the variables `src_mode` and `dst_mode` are defined.
> If `#ifdef lint` is not defined, these two variables are uninitialized.
> 
> In the `else` branch at line 1693, they are also not explicitly
> initialized,
> but `src_mode` is used later at lines 1707 and 1745, among other places.
> 
> It needs to be confirmed whether this constitutes using the variables
> before they are initialized, which could lead to undefined behavior.
> 
> Suggested Action
> ----------------
> - Review the relevant code paths to ensure `src_mode` and `dst_mode`
>    are properly initialized before use.
> - Consider initializing them at declaration to avoid undefined behavior:
> 
>      mode_t src_mode = 0;
>      mode_t dst_mode = 0;

Static analysis tools should define lint with coreutils.

If we've already tagged something with IF_LINT, then
we've already analyzed it's use as OK.

It's better to not initialize variables to non valid values,
as then you lose the benefit of runtime UMR analysis.

thanks,
Padraig.