[Octave-bug-tracker] [bug #54237] 'abs' function template hack in pr-output.cc is not portable

[Mike Miller]

URL:
  <http://savannah.gnu.org/bugs/?54237>

                 Summary: 'abs' function template hack in pr-output.cc is not
portable
                 Project: GNU Octave
            Submitted by: mtmiller
            Submitted on: Mon 02 Jul 2018 02:41:55 PM PDT
                Category: Configuration and Build System
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Build Failure
                  Status: Postponed
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: dev
        Operating System: Any

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Details:

The local 'abs' function template in pr-output.cc and marked with a 'FIXME'
comment is not a good general or portable solution. The intent here is to
create explicit 'abs' overrides for all signed and unsigned integer types to
avoid a GCC warning message about comparison between signed and unsigned
types.

In execution, this local 'abs' declaration has a few problems:

* Building with the Clang compiler on 64-bit GNU/Linux produces "warning:
unused function 'abs'" on the 'SPECIALIZE_UABS(long long)' template
instantiation, see bug #53650. On 64-bit systems, 'long long' and 'unsigned
long long' are never used by Octave.

* Building with GCC 4.9.2 on Solaris 10 fails to compile with an error message
"error: call of overloaded ‘abs(short int)’ is ambiguous", and likewise
for other integer types. For some reason the compiler is unable to declare
that the local template overloads for integer types are better than the
standard library floating-point 'abs' functions. See bug #54217 for the full
error message. Changing the names of the local function templates to 'xabs'
fixed this error.




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