[Issue 22] ModuleInfo not being generated for object files with "dmd -c"

June 15, 2006
Posted by d-bugmail
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http://d.puremagic.com/issues/show_bug.cgi?id=22





------- Comment #1 from sean@f4.ca  2006-06-14 21:31 -------
This issue has arisen in all of my attempts to build libraries on Linux and it was a showstopper until someone discovered that the problem could be avoided by adding a unittest block to problem modules as a way to force ModuleInfo to be created where it wouldn't be otherwise.  However, this solution is far from ideal, and it's confusing folks who want to build my library code themselves, as I don't want to make code changes simply to work around what appears to be a code generation problem.  Interestingly, Phobos is the only library I've encountered that doesn't exibit this problem, but I've been unable to determine why.  However, in my sleuthing today I ran across some code generation differences between Win32 and Linux that may help to shed some light on what's happening.  Here are the beginning segments of dmain2 as compiled on Win32 and on Linux for comparison:

---------- Win32 ----------

_TEXT   segment dword use32 public 'CODE'       ;size is 0
_TEXT   ends
_DATA   segment para use32 public 'DATA'        ;size is 148
_DATA   ends
CONST   segment para use32 public 'CONST'       ;size is 0
CONST   ends
_BSS    segment para use32 public 'BSS' ;size is 1
_BSS    ends
FLAT    group
        extrn   __d_assert
        extrn   __d_assert_msg
        extrn   __d_array_bounds
        extrn   __d_switch_error
        extrn   _main

        public  _no_catch_exceptions
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   ___alloca
        extrn   __except_list
        extrn   __ModuleInfo_3std1c5stdio
        extrn   __nullext
        wkext   __ModuleInfo_3std1c5stdio(__nullext)
        extrn   __ModuleInfo_3std1c6string
        wkext   __ModuleInfo_3std1c6string(__nullext)
        extrn   __ModuleInfo_3std1c6stdlib
        wkext   __ModuleInfo_3std1c6stdlib(__nullext)
        extrn   __ModuleInfo_6object
        wkext   __ModuleInfo_6object(__nullext)

---------- Linux ----------

FLAT    group
;File = dmain2.d
        public  _d_assert
        public  _d_assert_msg
        public  _d_array_bounds
        public  _d_switch_error
        public  no_catch_exceptions
        public  main
        public  _ModuleInfo_6dmain2
        extrn   _Dmodule_ref
        extrn   _ModuleInfo_3std1c5stdio
        extrn   _ModuleInfo_3std1c6string
        extrn   _ModuleInfo_3std1c6stdlib
        extrn   _ModuleInfo_6object

I don't entirely understand why the symbols apparently lack a leading underscore in the Linux code, but the real problem seems to be that the Linux code has no equivalent for the OMF wkext blocks which default all ModuleInfo references to __nullext.  If my understanding of the object file formats is correct, this suggests that the ModuleInfo blocks are optional in Win32 and are mandatory in Linux.  Is this correct?  And assuming so, could this be changed? Alternately, I would be very happy if someone could suggest a workaround that doesn't involve code changes.


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