Wasn't sure whether to post this to gcc Dev or Patches so its both to start with.
Its my first posting to this forum so first some background: I have a storage application to which I can record or retrieve files. Its multi-process C/C++ compiled to run on the SPARC platform. The problem is the maximum file size which can be stored is 4GB due to the size being internally conveyed using an unsigned integer. I need to extend the range so it accepts much larger files i.e. convert all uints to long longs. The approach at first was to work through the code line-by-line to locate and upsize all variables as required. The problem is there's almost a million lines of code and no guarantee every instance of filesize usage will be located & upsized. Another more elegant approach which came to mind was to somehow 'trap' the occurrence of *unsigned* integer overflow...or should that be wrapping - yes I know its completely acceptable behaviour. If I could get gcc to do this for me I could simply run a full suite of end-to-end functional testing then wait for the trap to fire and abort. After each abort I can identify the undersized variable (via the backtrace) then apply a fix and repeat the process. This approach guarantees I'll target all variables restricting >4GB file records. I'm not for a moment suggesting this be added as an option to gcc. I'm just wanting to build a temporary tool to serve a purpose as outlined above. Want I'm looking for are some fast-track, high-level pointers as to how to achieve this. Bear in mind I've spent a good week gazing at the gcc source but need some guidance to go forward. As a starting point I've had a stab at modifying the -ftrapv option to work with unsigned int arithmetic. Preliminary testing appears to work ok with test apps aborting when wrapping occurs (I'm also mindful of -ftrapv possibly being flaky according to some other posts). What I'm desperately lacking is the ability to also trap/abort when ANY unsigned int be it a function arg, return variable, local variable, etc WRAPS on being assigned or passed a value to large in RUNTIME. Any advice as detailed as you like in relation to the source would be very much appreciated. Thanks for taking the time to read this and any other ideas on how to do this are also welcome. -- View this message in context: http://www.nabble.com/unsigned-integer-wrap-%27trap%27.-tp24215937p24215937.html Sent from the gcc - Dev mailing list archive at Nabble.com.
