• Rel (8/8) Mar 20 2019 I tried compiling a simple Hello World on Windows
• kinke (11/19) Mar 20 2019 So you're comparing LDC with DMD, not GDC as the title suggests.

Rel <relmail rambler.ru> writes:

I tried compiling a simple Hello World on Windows
with the latest DMD and the latest stable LDC. DMD
compilation results in 239kb executable and LDC
compilation results in 500kb executable (more than
twice bigger). -Os and -flto=full didn't do anything
to the executable size. So I'm wondering why is that?
I thought that LDC compiled binaries should be smaller
due to different kinds of optimizations in LLVM.

kinke <noone nowhere.com> writes:

On Wednesday, 20 March 2019 at 10:28:24 UTC, Rel wrote:
 I tried compiling a simple Hello World on Windows
 with the latest DMD and the latest stable LDC. DMD
 compilation results in 239kb executable and LDC
 compilation results in 500kb executable (more than
 twice bigger). -Os and -flto=full didn't do anything
 to the executable size. So I'm wondering why is that?
 I thought that LDC compiled binaries should be smaller
 due to different kinds of optimizations in LLVM.

So you're comparing LDC with DMD, not GDC as the title suggests.

DMD on Windows defaults to 32-bit code *and* the DigitalMars C 
runtime, while a 64-bit LDC to 64-bit code and the MS runtime. 
Which runtime (static/dynamic) depends on whether you invoke LDC 
in a VS command prompt or in a naked cmd.exe, and can be tweaked 
via -mscrtlib. I guess that accounts for most of the size 
difference; just check your executables' DLL dependencies.

Try coupling `-flto=full` with 
`-defaultlib=phobos2-ldc-lto,druntime-ldc-lto`, that probably 
helps in reducing the size further.