On Thursday 23 December 2004 14:44, Roberto Bagnara wrote:

Hi there,

I am confused. Everything started when I tried to do un Cygwin what I usually do under GNU/Linux. I have a makefile rule that builds a stand-alone application as follows:

pl_clpq$(EXEEXT): ppl_swiprolog.o pl_clpq.o pl_clpq.pl ../tests/clpq.pl plld -cc $(CC) -c++ $(CXX) -ld $(CXX) -pl-options,-g,main., -o $@ $+ \ -L$(top_builddir)/src/.libs -lppl \ -L$(top_builddir)/Watchdog/.libs -lpwl \ @extra_libraries@

Notice the option `-pl-options,-g,main.,', which, unless I am mistaken, means that main/0 is the goal to be executed at startup. (I am not sure the final dot and comma should be there, by the way.) While the application built that way runs happily under GNU/Linux, under Cygwin it dies because, while main/0 it is defined, main/1 is not. However, accorting to the `-pl-options' above, main/0 should be called, not main/1: I don't understand who is looking for main/1 and why. So I made a couple of experiment on GNU/Linux and the result is confusing:

$ pl -g main ERROR: Undefined procedure: main/1 ERROR: However, there are definitions for: ERROR: main/0 $ pl -g main. ERROR: Undefined procedure: main/1 ERROR: However, there are definitions for: ERROR: main/0 $ pl -g foo ERROR: Prolog initialisation failed: ERROR: Undefined procedure: foo/0 $ pl -g foo. ERROR: Prolog initialisation failed: ERROR: Undefined procedure: foo/0

What is going on?

There is a library(main) which defines main/0, setup a sensible runtime environment, picks the arguments and calls main/1 with the provided arguments. This should not bother you if you nicely define main/0 yourself, but if it somehow picks up this definition, you loose.

Enjoy --- Jan