Re: dllwrap -> ld arg passing (Was: Re: [Mingw-users] dllwrap related bug? (possibly OT))

[Paul G. <pga...@co...>]

*blown away*

On 14 Sep 2003 at 11:56, Luke Dunstan wrote:

> 
> 
> I built this program:
> 
> ///////////////////////////////////////////////////////////////////
> 
> static unsigned long
> strhash (const char *str)
> {
>  const unsigned char *s;
>  unsigned long hash;
>  unsigned int c;
>  unsigned int len;
> 
>  hash = 0;
>  len = 0;
>  s = (const unsigned char *) str;
>  while ((c = *s++) != '\0')
>  {
>  hash += c + (c << 17);
>  hash ^= hash >> 2;
>  ++len;
>  }
>  hash += len + (len << 17);
>  hash ^= hash >> 2;
> 
>  return hash;
> }
> 
> /* Use the output file to create a image base for relocatable DLLs. */
> 
> static unsigned long
> compute_dll_image_base (const char *ofile)
> {
>  unsigned long hash = strhash (ofile);
>  return 0x60000000 | ((hash << 16) & 0x0FFC0000);
> }
> 
> int main(int argc, char *argv[])
> {
> if(argc != 2)
> return 1;
> printf("image base of '%s': 0x%08lX\n", argv[1],
> compute_dll_image_base(argv[1]));
> return 0;
> }
> 
> ///////////////////////////////////////////////////////////////////
> 
> 
> 
> And when I executed it:
> 
> $ ./imagbase.exe glwin32.dll
> image base of 'glwin32.dll': 0x6B180000
> $ ./imagbase.exe csfont.dll 
> image base of 'csfont.dll': 0x6B180000
> So the conclusion is that by chance these DLL names just happen to
> hash to the same value :-)

	Who would have thunk it...it just blows me away...I had my suspicions...thank you, Luke.  I really appreciate 
all the time you've put in to this.

> 
> If you would like to give them different base addresses then you must
> specify it manually:
> 
> gcc -shared ... -Wl,--image-base,0x5432000
> 
> dllwrap ... --image-base 0x54320000

	Ok.

	Looks like I am going to have to come up with a way to determine what to do if two different file names hash 
to an identical value.

	In the meantime, I will see what I can do to manually define the value via a makefile modificaiton of some 
sort.

	Thanks again, Luke, for all your energy on this.

	Paul G.

>     ----- Original Message ----- 
> From: Paul G. 
> To: min...@li... 
> Sent: Sunday, September 14, 2003 10:03 AM
> Subject: Re: dllwrap -> ld arg passing (Was: Re: [Mingw-users] dllwrap
> related bug? (possibly OT))
> 
> Thanks, Luke, for your quick reply.
> 
> On 12 Sep 2003 at 9:36, Luke Dunstan wrote:
> 
> > 
> > ----- Original Message ----- 
> > From: "Paul G." <pga...@co...>
> > To: <min...@li...>
> > Sent: Friday, September 12, 2003 7:15 AM
> > Subject: dllwrap -> ld arg passing (Was: Re: [Mingw-users] dllwrap
> > related bug? (possibly OT))
> > 
> > 
> > > Thanks Luke for all your earlier feedback, it was and is greatly
> > appreciated as it helped me to eliminate a
> > > number of erroneous possibilities, thanks again. Finally. After
> > > thinking
> > about your feedback, Luke, I was left with one
> > > single question:
> > >
> > > Does dllwrap args forwarded/passed to ld override the ld internal
> > > hashing
> > algorithm(s?) used for establishing .dll --
> > > image-base options?
> > 
> > I think so, but after building a minimal test DLL I found that the
> > "--image-base" option passed to dlltool/ld *is* derived from the DLL
> > filename exactly like the base address generated by "ld" when you
> > use "gcc -shared". What are the names and base addresses of the DLLs
> > that you are having problems with?
> 
> I am building the object code with the -g3 switch enabled. I don't
> know (or even think) that it could make any difference in the hashing.
> Even so, I felt it needed to be mentioned.
> 
> names reported image-base, option assignment
> csfont0x6B180000
> glwin320x6B180000
> 
> Paul G.