I tried different versions of DMD 2.057:
- compiled from sources in the release zip (Gentoo ebuild)
- using the 32-bit binaries in the release zip
- compiling the latest 32-bit version of DMD from the repository
I tried different compiler flags or no flags at all, compiled similar code
in C++ to see if the linker is ok and tried -m32 and -m64, all to no
avail. Then I found a solution that I can hardly imagine happening only on
my unique snow-flake of a system ;) :
struct Test {
__gshared byte abcd[10 * 1024 * 1024];
}
If it weren't for your own test results, I'd assume there is a small
compiler bug in the code that decides what can go into .bss, that makes it
look only for data explicitly flagged as __gshared, but not other
immutable data. (Something like that anyway.)
I back-tracked the compiler code to where it either calls obj_bytes (good
case, goes into .bss) or obj_lidata (bad case) to write the 10 MB of
zeros. But there were so many call sites, that I figured someone with
inside knowledge would figure it out faster.
As a side-effect of this experiment I found this combination to do funny
things at runtime:
--------------------------------------------------
struct Test {
byte arr1[1024 * 1024 * 10];
__gshared byte arr2[1024 * 1024 * 10];
}
int main() {
Test test;
return 0;
}
--------------------------------------------------
-- Marco
Am 18.01.2012, 11:18 Uhr, schrieb Walter Bright
<newshou...@digitalmars.com>:
On 1/18/2012 1:43 AM, Marco Leise wrote:
It is back again! The following struct in my main module increases the
executable size by 10MB with DMD 2.075:
struct Test {
byte abcd[10 * 1024 * 1024];
}
Compiling it and obj2asm'ing the result, and you'll see it goes into the
BSS segment:
_TEXT segment dword use32 public 'CODE' ;size is 0
_TEXT ends
_DATA segment para use32 public 'DATA' ;size is 12
_DATA ends
CONST segment para use32 public 'CONST' ;size is 0
CONST ends
_BSS segment para use32 public 'BSS' ;size is 10485760
_BSS ends
FLAT group
extrn _D19TypeInfo_S3foo4Test6__initZ
public _D3foo4Test6__initZ
FMB segment dword use32 public 'DATA' ;size is 0
FMB ends
FM segment dword use32 public 'DATA' ;size is 4
FM ends
FME segment dword use32 public 'DATA' ;size is 0
FME ends
extrn _D15TypeInfo_Struct6__vtblZ
public _D3foo12__ModuleInfoZ
_D19TypeInfo_S3foo4Test6__initZ COMDAT flags=x0 attr=x10 align=x0
_TEXT segment
assume CS:_TEXT
_TEXT ends
_DATA segment
_D3foo12__ModuleInfoZ:
db 004h,000h,000h,0ffffff80h,000h,000h,000h,000h
;........
db 066h,06fh,06fh,000h ;foo.
_DATA ends
CONST segment
CONST ends
_BSS segment
_BSS ends
FMB segment
FMB ends
FM segment
dd offset FLAT:_D3foo12__ModuleInfoZ
FM ends
FME segment
FME ends
_D19TypeInfo_S3foo4Test6__initZ comdat
dd offset FLAT:_D15TypeInfo_Struct6__vtblZ
db 000h,000h,000h,000h ;....
db 008h,000h,000h,000h ;....
dd offset FLAT:_D19TypeInfo_S3foo4Test6__initZ[03Ch]
db 000h,000h,0ffffffa0h,000h,000h,000h,000h,000h
;........
db 000h,000h,000h,000h,000h,000h,000h,000h ;........
db 000h,000h,000h,000h,000h,000h,000h,000h ;........
db 000h,000h,000h,000h,000h,000h,000h,000h ;........
db 000h,000h,000h,000h,000h,000h,000h,000h ;........
db 001h,000h,000h,000h,066h,06fh,06fh,02eh ;....foo.
db 054h,065h,073h,074h,000h ;Test.
_D19TypeInfo_S3foo4Test6__initZ ends
end
-------------------------------------------------
Adding a void main(){} yields an executable of 145,948 bytes.
