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LWN.net Weekly Edition for May 16, 2013
A look at the PyPy 2.0 release
PostgreSQL 9.3 beta: Federated databases and more
LWN.net Weekly Edition for May 9, 2013
(Nearly) full tickless operation in 3.10
Nice trick you pulled there, slipped "signed" in! Yes, that's true about signed overflow, but *NOT* unsigned overflow. Which makes the whole safety thing rather half-baked...
> Gcc and Clang could have such a feature in no time
In fact, that option already exists in GCC:
-ftrapv This option generates traps for signed overflow on addition, subtraction, multiplication operations.
Except, it doesn't work; it's been totally broken for over 5 years and nobody has stepped up to fix it yet.
Are they using the right technology?
Posted May 28, 2012 6:52 UTC (Mon) by ncm (subscriber, #165)
If anybody actually had any use for range-checked C, that mode in Gcc would work. Likewise, array bounds checking. The reason that people don't have any use for them is that they would fail to catch the overwhelming majority of overflow and overindexing bugs. A program that fails to keep a short int less than 32768 is a program that also fails to keep it below 10000. A program that overindexes its built-in arrays also overindexes variable-sized storage.
Posted May 28, 2012 13:25 UTC (Mon) by nix (subscriber, #2304)
Unsigned ints don't overflow. They implement well-defined modular arithmetic. No operations on unsigned int yield undefined results.
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