-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 'Way back in February I was musing about the possibility of a mfbt helper template that would allow us to silence "variable X might be used uninitialized" warnings without the negative effects of default-initializing those variables (mainly, that that could hide bugs if a variable *is* used uninitialized). I finally got around to implementing something, and it seems to work pretty well -- well enough for me to eliminate *all* of the maybe-uninitialized variable warnings in layout/. The patches are posted in this bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1032994
The basic idea is that anytime you get a "may be used uninitialized" warning, you can just change that variable's definition to CondSet<T> var; which silences the compile-time warning and adds debug-only, fatal runtime assertions that the variable is initialized at every point of use. You are somewhat limited in what you can do with such a variable; the most important restriction is that you can't pass it to a function with an out-parameter of type T* or T&. You must instead change that function to take CondSet<T>* or CondSet<T>&. This is because many such functions in our code base don't always write their out-parameters; passing a reference to the CondSet object allows us to track that dynamically and get the assertion right. Other restrictions of note (unlike the above, these could potentially change if it were needed) are that there is no copy constructor, and that you can't store a NaN in CondSet<float> or CondSet<double>. A remaining major flaw, which I would welcome help correcting, is that it also squelches "variable *is* used uninitialized" warnings. (I'm not sure this is possible to avoid, without asking the compiler folks for a new __attribute__ or similar.) I consider this to be preliminary work, so I'm asking for feedback here rather than r?ing any of the patches. zw -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 Comment: Using GnuPG with Icedove - http://www.enigmail.net/ iQIcBAEBCAAGBQJTsxuSAAoJEJH8wytnaapkPSgP/15z2cWBFenZjo+1FxXIiRWq tpteSKiFkmXB1aEYPSwkwH7pUJ44icHkixOSz6lYX4YdwCeYAWxCh5IlozCPLg81 4rGX0rql27oRd/RFnN9hNm/+zRtP/KKdjf94Tid6gDdW4k86Ce+AJ2QkkW/nL6JQ kWJ5NkESImyLLu50RawzZyj1o/eQFEXl4pixSrqLcQ1Ozs0/Z/BMb3QARgWFLQ/y AwTbe2IEfSogglhmZgh7RM8zwZmB/nkr2NRbsAwZ+qPrcEjmJntnzWq8ZrbBXJl6 OPlk8+lX6Vcrw3XgO/Olkr2Ie/tSuXgtL9PdVJVqnl2NJiq0UgX5Sms/PiqkohYQ ojE23ESghVIMd430PBtOLAWOhBI77zg/frzkW9dkW2sJnxocnahNkk77a9Ml9X/4 Hyj0O7verHu4N8IbgV0Ojg3M20tVx4LInM7flZwCqlGkHpT3ztctgdUfx9090Thx kx+0vMN5FAU7+GmNYzVuhweuVmrnfaympnbODlgNmrBLiWHrPdsHU8aoc1DH+ioG jFm7c+py6MsuI2Z7inxAMNq0jYaOHw9s4tckGWOTDMYSOzMXNh0XVKaROSnn+LID uBklD4yvYLafSbx/nCsQ5GapXysxmrZGGYW6LxcZ/NDYaZyLISGuV3JOxFygdgNH iVCi18PyVB0NJP1K5KAn =m+1i -----END PGP SIGNATURE----- _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
