#2727 gnuplot-6.0.1 "make check" fails in watchpoints.dem

[Ulrich Müller]

"make check" fails for gnuplot-6.0.1 on Gentoo Linux in file demo/watchpoints.dem:

*********************** file watchpoints.dem *********************
Plot title: plot FOO smooth cnormal
 watch y=.25 watch y=.50 watch y=.75
    Watch 1 target y = 0.25     (1 hits)
        hit 1   x 50.6  y 0.25
    Watch 2 target y = 0.5  (1 hits)
        hit 1   x 63.6  y 0.5
    Watch 3 target y = 0.75     (1 hits)
        hit 1   x 68.3  y 0.75

<cr> to continue<cr> to continue
    Variables beginning with INTERSECT:
    INTERSECT_X = 167.511137525825
    INTERSECT_Y = 20.2444312370877

<cr> to continue"watchpoints.dem" line 81: undefined function: FresnelC

make[3]: *** [Makefile:744: check-noninteractive] Error 1
make[2]: *** [Makefile:599: check-am] Error 2
make[1]: *** [Makefile:449: check-recursive] Error 1
make: *** [Makefile:432: check-recursive] Error 1

The problem is that function FresnelC only exists when gnuplot was configured to link against libcerf.

Attached patch fixes the problem for me.

[Ethan Merritt]

Applied, thanks. Although only the final plot needs to be skipped; the preceding plots do not depend on any special functions.