On 21/12/2011 03:18, Miles Bader wrote:
David Brown<david.brown@xxxxxxxxxxxx> writes:
David Brown<david@xxxxxxxxxxxxxxx> writes:
Making "-Wfloat-equal" a default flag would eliminate many of these
mistakes.
It also results in false positives, so it shouldn't be on by default.
[E.g. "float x = 0; .... y = x; ... if (y == 0) ..." should not result
in a warning.]
-Miles
I gather (from the bug report mentioned by Vincent Lefevre) that code
like this will not always give the result you expect - so the compiler
should definitely warn in such cases.
No. The bug cited by Vincent is a completely different case.
Calculation and assignment are not the same.
-Miles
My impression was that they were the same, or at least related, since
the calculations in the examples would probably be done in advance by
the compiler and reduced to simple assignments.
But I expect that you know the details a lot better than me. If the
compiler can guarantee consistent and expected results in cases like
yours involving simple assignments, then it would make sense to change
the "-Wfloat-equal" not to trigger in such situations. After all, the
point of the warning is to help users avoid code that might not do what
it seems to do - if it /does/ do the expected thing, then there is no
need of a warning.
In other words, the best course (IMHO) is to fix -Wfloat-equal to
eliminate common false positives, and /then/ enable it by default.
mvh.,
David
