option -lib difference from dmd

[smolt]

LDC: ldc2-0.13.0-alpha1-osx-x86_64.tar.xz

Issue description:
ldmd2 -lib option behaves different from dmd. dmd splits a D module into separate compilation units before building the library. ldmd2 does not split the module.

$ cat >testlib.d <<eof
void foo() {}
void bar() {}
void xyzzy() {}
eof
$ dmd -lib -oflibtest.a testlib.d
$ nm libtest.a

libtest.a(testlib.o):
0000000000000050 D _D7testlib12__ModuleInfoZ
0000000000000030 T _D7testlib15__unittest_failFiZv
0000000000000000 T _D7testlib7__arrayZ
0000000000000018 T _D7testlib8__assertFiZv
U __d_array_bounds
U __d_assertm
U __d_unittestm

libtest.a(testlib_1_144.o):
0000000000000000 S _D7testlib3fooFZv

libtest.a(testlib_2_135.o):
0000000000000000 S _D7testlib3barFZv

libtest.a(testlib_3_25e.o):
0000000000000000 S _D7testlib5xyzzyFZv

Also, noticed that dmd and ldmd2 default library naming is different when -of is not specified. dmd calls the library testlib.a where ldmd2 calls it libtestlib.a.

$ dmd --help
DMD64 D Compiler v2.064
Copyright (c) 1999-2013 by Digital Mars written by Walter Bright

$ ldmd2 --help
LDC - the LLVM D compiler (0.13.0-alpha1):
based on DMD v2.064 and LLVM 3.4

[redstar]

Thanks for the great report. It was easier to fix then I expected. :-)

[smolt]

Wow - that was fast! -lib will be nice for breaking up modules like dmain2.d which has the C main embedded in it. This should allow one to link in another C main() to replace dmain2 C main() without hacking runtime code. And could make for smaller statically linked executables!

[redstar]

As I said - it was easy to fix. I asked for the report because it helps to track issues (especially if I can't fix them in ten minutes. :-)

[smolt]

I missed something key here. Went to build phobos using -lib but found modules still not broken into multiple .o's. Turns out it is dmd -multiobj option that is not implemented in ldc. -multiobj breaks up a module into separate obj files, which should help make smaller apps when linking to phobos (link only the functions you need). I didn't realize what was going on until I searched the dmd source code and see that -multiobj is turned on by -lib automatically. Idmd2 accepts -multiobj but does not use.