Bug#1075172: libgraphics-libplot-perl: ftbfs with GCC-14

[Étienne Mollier]

Control: tags -1 confirmed

Relevant part of the failure is:

	Libplot.xs:91:13: error: ‘return’ with no value, in function returning non-void [-Wreturn-mismatch]
	   91 |             return __BEGIN_DECLS;
	      |             ^~~~~~
	Libplot.xs:24:1: note: declared here
	   24 | constant(name, arg)
	      | ^~~~~~~~
	Libplot.xs:97:13: error: ‘return’ with no value, in function returning non-void [-Wreturn-mismatch]
	   97 |             return __END_DECLS;
	      |             ^~~~~~
	Libplot.xs:24:1: note: declared here
	   24 | constant(name, arg)
	      | ^~~~~~~~

__BEGIN_DECLS and __END_DECLS look to be defined in util/plot.h
and are empty when compiling with a C compiler, or contain
guards for C code when compiling with a C++ compiler:

	# define __BEGIN_DECLS extern "C" {
	# define __END_DECLS   }

Which means `return __BEGIN_DECLS` and `return __END_DECLS` make
actually not much sense.  Compiling with gcc, they are empty,
thus the return mismatch error.  Compiling with g++ would likely
result in more spectacular compiler complaints.  I have little
understanding of the intent behind these return values, and do
not know whether to make them return 0, 1 or something else.
The function signature is to return a static double length
floating point value, but the nearest approximation of a double
value to be returned would have been LIBPLOTPERL_VERSION if it
weren't commented out.

As it is, I don't see an obvious way forward apart from putting
dust back below the carpet and ignoring the error, and I would
question whether this function is behaving as intended in the
first place.

In hope this gives some leads,
-- 
  .''`.  Étienne Mollier <emollier at debian.org>
 : :' :  pgp: 8f91 b227 c7d6 f2b1 948c  8236 793c f67e 8f0d 11da
 `. `'   sent from /dev/pts/0, please excuse my verbosity
   `-    on air: Dixie Dregs - Peaches En Regalia
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