1073716 - clang 3.5 warnings for "using integer absolute value function 'abs' when argument is of floating point type [-Wabsolute-value]"

Status: RESOLVED FIXED

(Core :: General, defect)

Comment 1

[Daniel Holbert [:dholbert]]

Using clang 3.5 on Ubuntu 14.10 final beta (which is a trunk-ish version of clang -- newer than 3.5 in Ubuntu 14.04), I get several warnings like this when building m-c, which break my build because they're in FAIL_ON_WARNINGS directories:

{
gfx/2d/Path.cpp:255:43: error: using integer absolute value function 'abs' when argument is of floating point type [-Werror,-Wabsolute-value]
 1:02.30     t = 2 * Float(sqrt(aTolerance / (3. * abs(s3))));
 1:02.30                                           ^
}

Here, s3 is float-typed, as the warning text says. In another instance, we get the same warning for an int64_t.

This happens because "abs" comes from C, and is documented here as just taking "int". Other types have their own differently-named functions "fabs", "fabsl", "labs", and "llabs" (in C):
  http://en.cppreference.com/w/c/numeric/math/abs

Fortunately, C++ has std::abs which seems to have versions for pretty much any numeric type:
  http://en.cppreference.com/w/cpp/numeric/math/abs
  http://en.cppreference.com/w/cpp/numeric/math/fabs
...which is why the warning-text recommends using it.

Comment 2

[Daniel Holbert [:dholbert]]

Attachment: fix v1

Comment 3

[Daniel Holbert [:dholbert]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/7a4c925ca8d7

Comment 4

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/7a4c925ca8d7