I have compiled a small D program with LDC2 on Windows32, with and without -g and I have stripped it. Here are the resulting binary sizes:

2.166.124 test.exe  (1)
4.421.713 test_g.exe (2)
  853.518 test_stripped.exe (3)
1.204.750 test_g_stripped.exe (4)

What's the difference between the stripped (3) and the stripped program compiled with -g (4)?

Is it a good idea to make ldmd2 also strip the exe binary if the -g switch is not used?

Bye,
bearophile

On 18 Jun 2013, at 1:09, bearophile wrote:
> What's the difference between the stripped (3) and the stripped program compiled with -g (4)?

If you build with -g, the debug version of druntime/Phobos is linked instead.

> Is it a good idea to make ldmd2 also strip the exe binary if the -g switch is not used?

Probably not, as that typically also makes backtraces rather unusable. We should look into other ways to reduce the executable size at some point though – currently, we don't allow the linker to easily strip out as much unused data as there would be possible (along the lines of -ffunction-sections resp. --gc-sections).

One thing I also want to look into is to automatically internalize everything on building executables that is not needed to be visible (like _Dmain, which is called from druntime). It would e.g. allow the LLVM optimizer to discard functions that have been inlined into all their callers, etc.

David

David Nadlinger:

> If you build with -g, the debug version of druntime/Phobos is linked instead.

I see.


>> Is it a good idea to make ldmd2 also strip the exe binary if the -g switch is not used?
>
> Probably not, as that typically also makes backtraces rather unusable.

On Windows32 with dmd the backtraces are unusable if you don't compile with -g.

This is a little program:

void main() {
    throw new Exception(null);
}


If you compile it with dmd -g you get at run-time:

object.Exception@test.d(2)
----------------
0x00402044 in _Dmain at ...\test.d(2)
0x0040292C in extern (C) int rt.dmain2._d_run_main(int, char**, extern (C) int function(char[][])*).void runMain()
0x004029BC in extern (C) int rt.dmain2._d_run_main(int, char**, extern (C) int function(char[][])*).void runAll()
...


If you don't use -g:

object.Exception@test.d(2)
----------------
0x0040203D
0x00402914
0x00402231
0x00402054
...


Bye,
bearophile

On Wednesday, 19 June 2013 at 06:14:34 UTC, David Nadlinger wrote:
> On 18 Jun 2013, at 1:09, bearophile wrote:
>> What's the difference between the stripped (3) and the stripped program compiled with -g (4)?
>
> If you build with -g, the debug version of druntime/Phobos is linked instead.
>


I was going to ask why a test app build with 'ldmd2 -inline -release -O -g' appears to be quite a bit slower than one built with 'ldmd2 -inline -release -O', and I suppose that answers that question as well?


(I thought i'd run it through the Very Sleepy Profiler to compare it with the version build with DMD. If i compile without -g then it works but I get no function names, and if I compile it with -g the profiler crashes (Doesn't seem to be an LDC issue though - It seems to have issues with Mingw 3.8 in general).