Re: What exactly does the compiler switch -betterC do?
On Wednesday, 5 October 2016 at 12:42:14 UTC On Wednesday, 5 October 2016 at 12:42:14 UTC, Jacob Carlborg wrote: No. There's a difference between DMD 2.070.0 and 2.071.0: OK, I'll retry on OSX, the bug report said Linux though. Seems like we're dragging in all of the _Dmain stuff. IIRC _Dmain is marked as weak in some extra C file, but the problem might be unrelated to that. https://issues.dlang.org/show_bug.cgi?id=16547
Re: What exactly does the compiler switch -betterC do?
On 2016-10-05 11:39, Martin Nowak wrote:
Because you're linking with druntime/phobos which drags in plenty of
symbols (including a GC). Also Jakob is showing the symbols of the
object file, not executable.
No. There's a difference between DMD 2.070.0 and 2.071.0:
$ cat main.d
module main;
extern (C) int printf(in char*, ...);
extern (C) void main()
{
printf("asd\n");
}
$ dvm use 2.070.0
$ dmd --version
DMD64 D Compiler v2.070.0
Copyright (c) 1999-2015 by Digital Mars written by Walter Bright
$ dmd -betterC main.d
$ nm main | wc -l
4
$ dvm use 2.071.0
$ dmd --version
DMD64 D Compiler v2.071.0
Copyright (c) 1999-2015 by Digital Mars written by Walter Bright
$ dmd -betterC main.d
$ nm main | wc -l
2428
Note that "main" is declared as "extern (C)", which makes all the
difference.
--
/Jacob Carlborg
Re: What exactly does the compiler switch -betterC do?
On Monday, 19 September 2016 at 21:09:39 UTC, Gary Willoughby wrote: On Monday, 20 June 2016 at 06:35:32 UTC, Jacob Carlborg wrote: On 2016-06-19 21:53, Gary Willoughby wrote: If compiled with -betterC, it contains these: T _main U _printf I get significantly more symbols than that when compiling the following program any idea why? Because you're linking with druntime/phobos which drags in plenty of symbols (including a GC). Also Jakob is showing the symbols of the object file, not executable.
Re: What exactly does the compiler switch -betterC do?
On Tuesday, 20 September 2016 at 13:23:35 UTC, Jacob Carlborg wrote: On 2016-09-19 23:09, Gary Willoughby wrote: $ rdmd --build-only --force -betterC -de -O -inline -release -w test.d $ nm test Indeed. I just noticed now that there's a difference between 2.070.0 and 2.071.0. I get 4 symbols with 2.070.0 and 2428 with 2.071.0. I would say it's a bug. Filed: https://issues.dlang.org/show_bug.cgi?id=16547
Re: What exactly does the compiler switch -betterC do?
On 2016-09-21 02:25, Anonymouse wrote: On Monday, 20 June 2016 at 06:35:32 UTC, Jacob Carlborg wrote: It is intended to allow you to link an application without druntime. [...] What is the equavilent in gdc and ldc? No idea, try ldc/gdc --help ;) -- /Jacob Carlborg
Re: What exactly does the compiler switch -betterC do?
On Monday, 20 June 2016 at 06:35:32 UTC, Jacob Carlborg wrote: On 2016-06-19 21:53, Gary Willoughby wrote: When compiling, what exactly does the -betterC flag do? The command help says "omit generating some runtime information and helper functions" but what does this really mean? Is there any specifics somewhere? It is intended to allow you to link an application without druntime. [...] What is the equavilent in gdc and ldc?
Re: What exactly does the compiler switch -betterC do?
On 2016-09-19 23:09, Gary Willoughby wrote: $ rdmd --build-only --force -betterC -de -O -inline -release -w test.d $ nm test Indeed. I just noticed now that there's a difference between 2.070.0 and 2.071.0. I get 4 symbols with 2.070.0 and 2428 with 2.071.0. I would say it's a bug. -- /Jacob Carlborg
Re: What exactly does the compiler switch -betterC do?
On Monday, 20 June 2016 at 06:35:32 UTC, Jacob Carlborg wrote:
On 2016-06-19 21:53, Gary Willoughby wrote:
When compiling, what exactly does the -betterC flag do? The
command help
says "omit generating some runtime information and helper
functions" but
what does this really mean? Is there any specifics somewhere?
It is intended to allow you to link an application without
druntime. A Hello World using "extern(C) main" and printing
using "printf" contains the following symbols on OS X:
00a8 S _D4main12__ModuleInfoZ
0068 T _D4main15__unittest_failFiZv
0018 T _D4main7__arrayZ
0040 T _D4main8__assertFiZv
00b5 s _TMP1
U __d_arraybounds
U __d_assert
U __d_unittest
T _main
U _printf
If compiled with -betterC, it contains these:
T _main
U _printf
I get significantly more symbols than that when compiling the
following program any idea why?
import core.stdc.stdio;
extern(C) void main()
{
printf("Hello World!\n");
}
$ rdmd --build-only --force -betterC -de -O -inline -release -w
test.d
$ nm test
Re: What exactly does the compiler switch -betterC do?
On 2016-06-19 21:53, Gary Willoughby wrote: When compiling, what exactly does the -betterC flag do? The command help says "omit generating some runtime information and helper functions" but what does this really mean? Is there any specifics somewhere? It is intended to allow you to link an application without druntime. A Hello World using "extern(C) main" and printing using "printf" contains the following symbols on OS X: 00a8 S _D4main12__ModuleInfoZ 0068 T _D4main15__unittest_failFiZv 0018 T _D4main7__arrayZ 0040 T _D4main8__assertFiZv 00b5 s _TMP1 U __d_arraybounds U __d_assert U __d_unittest T _main U _printf If compiled with -betterC, it contains these: T _main U _printf -- /Jacob Carlborg
Re: What exactly does the compiler switch -betterC do?
On Sunday, 19 June 2016 at 19:53:46 UTC, Gary Willoughby wrote: When compiling, what exactly does the -betterC flag do? The command help says "omit generating some runtime information and helper functions" but what does this really mean? Is there any specifics somewhere? My understanding was that -betterC was not fully implemented yet, due mostly to tight compiler integration with the runtime. (old info?) I'm not super smart on the DMD source, but it looks like betterC prevents genhelpers() and genModuleInfo() from being called, with "helpers" appearing to be array checking, asserts and unit tests. A comparison of object files compiled with and without the flags shows just a small reduction in the size of the code, but grepping for bounds checking, unit tests and ModuleInfo in the -betterC generated object file shows they are missing. Hope this helps, -Jon
