On Mon, 2011-01-24 at 10:55 -0500, Nicolas Pitre wrote: > On Mon, 24 Jan 2011, Tony Olech wrote: > > > On Mon, 2011-01-24 at 09:43 -0500, Nicolas Pitre wrote: > > > Uninitialized global scope variables are by definition assigned to the > > > .bss section. The .bss section is dynamically allocated at run time > > > rather than being stored in the compiled binary, and also cleared to > > > zero at run time. So the preference is for zero-initialized global > > > variables not to be initialized at all because 1) they are implicitly > > > initialized to zero anyway, and 2) that makes the resulting binaries > > > smaller. > > > So this is not about fixing a bug, but rather to conform to the adopted > > > policy for kernel code. > > > Nicolas > > Thanks for the reply. I had not realized that saving 20 bytes on the > > binary size was so important. > With the size of the kernel they add up. > > How then can one do static code analysis > > to determine which uninitialized variables are uninitialized as > > a result of a bug? > A good static code analysis tool should know already that uninitialized > global variables are implicitly initialized to zero. This is not the > case for local variables of course > Nicolas Thanks for the reply. I had assumed that for a module the global initialized variables were loaded at module load. That then is a problem given that new devices (and drivers) are appearing quite rapidly. I therefore do not understand how the global initialized variables from an externally compiled kernel module get added into the kernel image - does "depmod" do that? A good static code analysis tool surely can only show a list of uninitialized static global variables leaving it for the user to trawl through and decide which are OK and which are not - so much easier if one has no uninitialized static global variables to start with. Tony Olech
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