[PATCH] Add a 'no-asserts' requirement option to LIT.
resistor at mac.com
Tue Feb 3 12:47:05 PST 2015
> On Feb 3, 2015, at 12:32 PM, David Blaikie <dblaikie at gmail.com> wrote:
> On Tue, Feb 3, 2015 at 12:19 PM, Mehdi Amini <mehdi.amini at apple.com <mailto:mehdi.amini at apple.com>> wrote:
> Hi David,
>> On Feb 3, 2015, at 11:15 AM, David Blaikie <dblaikie at gmail.com <mailto:dblaikie at gmail.com>> wrote:
>> On Tue, Feb 3, 2015 at 11:03 AM, Owen Anderson <resistor at mac.com <mailto:resistor at mac.com>> wrote:
>> Hi chandlerc, joker.eph,
>> This is useful when checking diagnostics and annotations that are only enabled in asserts mode.
>> Not sure I quite follow - "REQUIRES: Asserts" would be used for any test case that's verifying a failure that's only enabled in asserts mode. "REQUIRES: no-asserts" would be for testing the absence of that same failure in a no-asserts build?
>> That seems like a thing I wouldn't want to test for. The idea is that the program has undefined behavior if it would assert but you're in a non-asserts build. That's not a thing to test for - there's no specific/guaranteed behavior in that case.
> To provide you with more context: I am expecting some optional metadata from the front-end, but in case they are malformed for any reason I want to be bullet proof and handle this case gracefully (i.e. undefined behavior / crashing is not acceptable). So I’d like my assert build to verify the validity of the metadata but my release build to ignore it and set a suitable default value that I know allows recovery most of the time.
> I can’t add a test to check if we recover correctly from an invalid metadata without this.
> This is valid in general for the category of assertions we put to enforce some invariant/properties that are important for optimization purposes but does not prevent us from generating a correct code if they are broken.
> Does it make sense?
> Not sure how everyone else feels, but I'd rather classify something like that that has well-defined recovery semantics, as something other than 'validity'.
> When/where/how do you expect invalid metadata to come into your system?
We do on-line compilation of IR from frontends other than clang, and from serialized formats other than native bitcode. We *expect* that the frontends/serializers will give us well-formed inputs, and we want to detect and error on cases where fail that during normal development and testing cycles. However, in deployment, we never want a user to see the compiler crash, so we suppress the error and attempt to recover in production builds. We want to be able to write tests that are expected to crash in asserts build and expected *not* to crash in release builds for exactly this reason.
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