I've just had an enlightening few hours getting pcre-ocaml to compile under
Windows (I tried a few years ago and, very lazily, just gave up). I've
managed to get it to work but I'm wondering whether anyone else has done
this and, if so, whether they can explain/confirm/correct a couple of the
steps involved. I'm very much indebted to Alain Frisch's instructions for
building PCRE under OCaml 3.10.0 which are part of the CDuce distribution or
I would've been completely at sea with this!

The main thing that's got me puzzled is the renaming of libpcre.dll.a and
libpcre.a that I have to do to get the thing to link.

Note that I'm building the "official" way - so MinGW running within Cygwin.

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+++
Building pcre for MinGW
  (Ensure that Cygwin's PCRE libraries are *not* installed)
  Unpacked PCRE 7.8
  ./configure --prefix="C:/Dev/OCaml" \          # set to install PCRE
              --includedir="C:/Dev/OCaml/lib" \  # to my OCaml tree.
              --disable-cpp \                    # from Alain's
instructions.
              --enable-utf8 \                    # Similarly.
              --build=mingw32 \                  # MinGW, not Cygwin build
              CC="gcc -mno-cygwin"               # Necessary to ensure that
                                                 # autoconf detects the
correct
                                                 # library and include dirs 
                                                 # when querying gcc (CFLAGS
                                                 # won't work here)
  make
  make install

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+++
Building pcre-ocaml
  (Note that with older (< 0.14) versions of flexlink, the linker errors
noted doesn't show up and the resulting library is broken)
  Unpacked pcre-ocaml 5.15.1
  Edit pcre-ocaml-release-5.15.1/Makefile.conf to contain:
    export LIBDIRS := C:/Dev/OCaml/lib # Location of PCRE
    export MINGW=1                     # MinGW build
    export CC=gcc                      # Or you get lots of errors!
  patch -p0 -i pcre-ocaml-release-5.15.1.patch # (attached)

  The patch "fixes" two things in OCamlMakefile
    a) It causes the ocamlc -where check to pass the result through cygpath.
My OCAMLLIB variable is correctly set (for Windows) as C:\Dev\OCaml\lib and
Cygwin configure scripts should generally respect that (build in Cygwin, run
in Windows so OCAMLLIB is a Windows environment variable...). I've been lazy
though and not done the same thing for the camlp4 -where test...
    b) It adds a simple check for OCaml 3.11 (it would be better if it did a
>= 3.11 check but I haven't bothered to bring up the GNU make info pages to
check the syntax for doing that!) and uses ocamlmklib instead of manually
building the stub libraries if OCaml 3.11 is found - the manual build
instructions included in OCamlMakefile are for 3.10 and earlier and so don't
work (i.e. non-flexlink linking)

  OK, so at this stage it looks as though we should be ready to build. But
if I run make (with flexlink 0.14 or later) then I get the following errors
(compiling with flexlink 0.13 works, but the resulting library is broken):

ocamlmklib -LC:/Dev/OCaml/lib -o pcre_stubs  pcre_stubs.o -lpcre
c:\Users\DRA\AppData\Local\Temp\dyndll8e6a10.o:pcre_stubs.c:(.text+0x205):
undefined reference to `__imp__pcre_callout'
[and several more missing __imp__pcre_... messages]

  The problem is in C:\Dev\OCaml\lib, it appears. In there are libpcre.a,
libpcre.dll.a and libpcre.la. If I rename libpcre.a to libpcre.old.a and
then libpcre.dll.a to libpcre.a then the build works and the resulting
library builds. As far as I can tell, this is something to do with libtool
but I know very little about this - is the inability of the library to link
without renaming these files something to do with using flexlink as the
linker? If I link a test program in C using -lpcre then it works - but is
that because gcc knows how to read .la files and looks for the libpcre.dll.a
file correctly?

  However, once this is followed through, the library does correctly build
and install - and the examples all seem to be working. So, finally, it's
cheerio to the Str module for me :o)

  Any pointers appreciated!


David