[P5P] [PATCH] CYG14 Dynaloader without -DUSEIMPORTLIB, and search cyg prefix

Hi Reini,

Reini Urban wrote:

I'm not sure I follow the second part of your patch. In DynaLoader's
Makefile.PL, you add:

+sub MY::cflags {
+ package MY;
+ my $flags = shift->SUPER::cflags(@_);
+ if ($flags =~ /-DUSEIMPORTLIB/m) {
+ $flags =~ s/-DUSEIMPORTLIB/-UUSEIMPORTLIB/m;
+ }
+ $flags;
+}


I wonder
a) what USEIMPORTLIB does in the first place (grep doesn't come up with
copious docs)
b) if it is wise to more or less unconditionally remove it.
c) why you're doing the if() if s/// simply not matching has the same
effect.

Finally, could you add a somewhat more descriptive commit message? It's
not clear to me and I believe that will apply to a lot of other people
as well.

Cheers,
Steffen

With -DUSEIMPORTLIB it simply fails, because the importlib symbolnames
are used,
e.g. __imp__PL_stack_sp and not the direct name _PL_stack_sp.

g++-4 -o cygperl5_13_4-nt.dll --shared -Wl,--enable-auto-import
-Wl,--export-all-symbols -Wl,--stack,8388608
-Wl,--enable-auto-image-base -L/usr/local/lib -fstack-protector
-Wl,--out-implib=libperl.dll.a -Wl,--image-base,0x52000000 op.o perl.o
madly.o malloc.o gv.o toke.o perly.o pad.o regcomp.o dump.o util.o
mg.o reentr.o mro.o hv.o av.o run.o pp_hot.o sv.o pp.o scope.o
pp_ctl.o pp_sys.o doop.o doio.o regexec.o utf8.o taint.o deb.o
universal.o globals.o perlio.o perlapi.o numeric.o mathoms.o locale.o
pp_pack.o pp_sort.o cygwin.o DynaLoader.o Win32CORE.o -ldl -lcrypt
Creating library file: libperl.dll.a
DynaLoader.o: In function `XS_DynaLoader_dl_undef_symbols':
/usr/src/perl/blead/buildnothreads/ext/DynaLoader/DynaLoader.c:346:
undefined reference to `__imp__PL_stack_sp'
/usr/src/perl/blead/buildnothreads/ext/DynaLoader/DynaLoader.c:346:
undefined reference to `__imp__PL_markstack_ptr'
/usr/src/perl/blead/buildnothreads/ext/DynaLoader/DynaLoader.c:346:
undefined reference to `__imp__PL_stack_base'
DynaLoader.o: In function `XS_DynaLoader_dl_error':
Yes. Using the importlib names can only link against the importlib
(the .dll.a), but not against the libperl objects directly.

From outside linking against libperl (the dll) is faster, and more
flexible. All modern gcc linkers
can link directly against a dll. Only Module::Build links against the
.dll.a, all other extutils against libperl.
Sure.

Hi Reini,

thanks for your reply and clarifications.

Reini Urban wrote:
So -DUSEIMPORTLIB / -UUSEIMPORTLIB has an effect on the symbol names.
Okay. Does this affect only cygwin? Should this affect only cygwin?
What's the significance on other platforms?
I'm not an expert in these matters, hence my questions. With
"unconditionally", I was at least partly wondering whether it should be
applied to cygwin (or win32+cygwin) only. Can you elaborate on that?
Do be honest, it seems to obscure things only for someone who knows
Perl. ("What's the significance of the extra condition? This must have
been added for some effect!")

Can you please just use a single s/.../.../m?
Wow. That is indeed quite a long message now. Maybe skip the giant
g++-linking part of the message.

Best regards,
Steffen

It possibly affects every platform which adds DynaLoader static and
uses importlibs.
To my knowledge only AIX, cygwin and mingw do this.
For cygwin we avoid importlibs for perl, but they are a nice to have, if
someone does not know the exact dll name (though this is what libperl is for).
On other POSIX platforms you do a symlink of libperl.so to the real
so, so don't
have to use the importlib jumps.
As said above. Linking statically with -DUSEIMPORTLIB is wrong, so it
affects every platform. But I only got the linking error with cygwin.
I guess mingw and AIX link in two steps, so they take the indirect route.
Can some porter over there please comment?
But that's the important part :) I trimmed it to the essentials.