Resolve ambiguous abs() call

[cwilling]

Signed-off-by: Christoph Willing chris.willing@linux.com

This resolves compilatin problem:

error: call of overloaded 'abs(double)' is ambiguous`

by using fabs(double) from cmath rather than trying abs(int) from stdlib.h or std::abs(long long int) from cstdlib

[codecov-io]

Codecov Report

Merging #439 into develop will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff            @@
##           develop     #439   +/-   ##
========================================
  Coverage    42.37%   42.37%           
========================================
  Files          129      129           
  Lines        13276    13276           
========================================
  Hits          5626     5626           
  Misses        7650     7650

Impacted Files	Coverage Δ
src/KeyFrame.cpp	76.65% <100%> (ø)	⬆️

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[ferdnyc]

Hmmm. OOC, is the call still ambiguous if it's written as std::abs()?

I have no objection to the use of std::fabs() instead, especially if it solves build problems, just trying to get a handle on the issue. (And always on the lookout for issues potentially caused by the IMHO-bad practice of using namespace std; in our code.)

What compiler/system gave you that error, BTW? Compiling with the various GCC and Clang versions in our CI matrix didn't flag it, interestingly.

[cwilling]

Yes the problem remains when using std::abs(). From the error msg the compiler seems to find only int abs(int) (from stdlib.h), or long int std::abs(long int) and long long int std::abs(long long int) (both from cstdlib). Since we want abs(double), using fabs() resolves the problem.

It could be due to age of compiler gcc-g++-5.5.0 but we're stuck with that on Slackware 14.2 until release of 15.0 which has gcc-g++-9.2.0 (probably still some months away).

Here's the full error message:

/var/tmp/SBo/libopenshot-0.2.4/src/KeyFrame.cpp: In function 'double {anonymous}::InterpolateBezierCurve(const openshot::Point&, const openshot::Point&, double, double)':
/var/tmp/SBo/libopenshot-0.2.4/src/KeyFrame.cpp:74:27: error: call of overloaded 'abs(double)' is ambiguous
    if (std::abs(target - x) < allowed_error) {
                           ^
In file included from /usr/include/c++/5.5.0/cstdlib:72:0,
                 from /usr/include/c++/5.5.0/ext/string_conversions.h:41,
                 from /usr/include/c++/5.5.0/bits/basic_string.h:5352,
                 from /usr/include/c++/5.5.0/string:52,
                 from /usr/include/c++/5.5.0/bits/locale_classes.h:40,
                 from /usr/include/c++/5.5.0/bits/ios_base.h:41,
                 from /usr/include/c++/5.5.0/ios:42,
                 from /usr/include/c++/5.5.0/ostream:38,
                 from /usr/include/c++/5.5.0/iostream:39,
                 from /var/tmp/SBo/libopenshot-0.2.4/src/../include/KeyFrame.h:34,
                 from /var/tmp/SBo/libopenshot-0.2.4/src/KeyFrame.cpp:31:
/usr/include/stdlib.h:774:12: note: candidate: int abs(int)
 extern int abs (int __x) __THROW __attribute__ ((__const__)) __wur;
            ^
In file included from /usr/include/c++/5.5.0/ext/string_conversions.h:41:0,
                 from /usr/include/c++/5.5.0/bits/basic_string.h:5352,
                 from /usr/include/c++/5.5.0/string:52,
                 from /usr/include/c++/5.5.0/bits/locale_classes.h:40,
                 from /usr/include/c++/5.5.0/bits/ios_base.h:41,
                 from /usr/include/c++/5.5.0/ios:42,
                 from /usr/include/c++/5.5.0/ostream:38,
                 from /usr/include/c++/5.5.0/iostream:39,
                 from /var/tmp/SBo/libopenshot-0.2.4/src/../include/KeyFrame.h:34,
                 from /var/tmp/SBo/libopenshot-0.2.4/src/KeyFrame.cpp:31:
/usr/include/c++/5.5.0/cstdlib:166:3: note: candidate: long int std::abs(long int)
   abs(long __i) { return __builtin_labs(__i); }
   ^
/usr/include/c++/5.5.0/cstdlib:174:3: note: candidate: long long int std::abs(long long int)
   abs(long long __x) { return __builtin_llabs (__x); }
   ^
src/CMakeFiles/openshot.dir/build.make:638: recipe for target 'src/CMakeFiles/openshot.dir/KeyFrame.cpp.o' failed
make[2]: *** [src/CMakeFiles/openshot.dir/KeyFrame.cpp.o] Error 1
CMakeFiles/Makefile2:161: recipe for target 'src/CMakeFiles/openshot.dir/all' failed
```

[ferdnyc]

Huh... so odd that it still considers abs from stdlib.h a candidate. But since there are two std::abs() candidates, it's kind of immaterial. And, indeed, fabs() is used at multiple other points in the code. I'm good with it! Merging, thanks.