gcj, gdb warnings & jni method signatures

[Rutger Ovidius]

Friday, September 17, 2004, 10:22:32 AM, you wrote:

TT> I would suggest starting your search in jni.cc:_Jv_LookupJNIMethod.
TT> There is probably some kind of buffer overwrite bug in the Windows
TT> specific code.

TT> Tom

Hi,

Thanks for the pointer. I put in some more printf debug lines and it
led me to the find_symbol function in natRuntime.cc (specifically, the
call to lt_dlsym)

The method signatures are different if the .dll is MSVC/gcc/borland,
etc, so _Jv_LookupJNIMethod tries a bunch.  SWT is compiled with msvc
(which prepends a "_").

But, the warning pops up before it even gets to the right signature.
I can't explain this at all.

The current signature in swt.dll:
Java_org_eclipse_swt_internal_win32_OS_CreateFontIndirectW__Lorg_eclipse_swt_internal_win32_LOGFONTW_2

But if I change it to:

Java_org_eclipse_swt_internal_win32_OS_CreateFontIndirectW
There is no warning.

Any more suggestions on what to consider next?




natRuntime.cc:

static int
find_symbol (lt_dlhandle handle, lt_ptr data)
{ 
  lookup_data *ld = (lookup_data *) data;
  fprintf (stderr, "before_dlsym %d : %s\n", strlen(ld->symname), ld->symname);
  ld->result = lt_dlsym (handle, ld->symname);
  fprintf (stderr, "after_dlsym %d\n", ld->result);
  return ld->result != NULL;
}


In gdb:

---
...
before_dlforeach
before_dlsym 62 : _Java_org_eclipse_swt_internal_win32_OS_CreateFontIndirectW@12
after_dlsym 0
before_dlsym 62 : _Java_org_eclipse_swt_internal_win32_OS_CreateFontIndirectW@12
warning: HEAP[ostest.exe]:
warning: Invalid Address specified to RtlFreeHeap( 00240000, 0022F800 )


Program received signal SIGTRAP, Trace/breakpoint trap.
0x77f767ce in ntdll!DbgUiConnectToDbg () from ntdll.dll
(gdb) c
Continuing.
after_dlsym 0
after_dlforeach
xyz
still null
before_dlforeach
before_dlsym 61 : Java_org_eclipse_swt_internal_win32_OS_CreateFontIndirectW@12
after_dlsym 0
before_dlsym 61 : Java_org_eclipse_swt_internal_win32_OS_CreateFontIndirectW@12
after_dlsym 0
after_dlforeach
now what
buf is _Java_org_eclipse_swt_internal_win32_OS_CreateFontIndirectW_12
after memcpy
before_dlforeach
before_dlsym 102 : Java_org_eclipse_swt_internal_win32_OS_CreateFontIndirectW__Lorg_eclipse_swt_internal_win32_LOGFONTW_2
after_dlsym 0
before_dlsym 102 : Java_org_eclipse_swt_internal_win32_OS_CreateFontIndirectW__Lorg_eclipse_swt_internal_win32_LOGFONTW_2
after_dlsym 0
after_dlforeach
after lookup
buf is after cat _Java_org_eclipse_swt_internal_win32_OS_CreateFontIndirectW__Lorg_eclipse_swt_internal_win32_LOGFONTW_2@12
before_dlforeach
before_dlsym 106 : _Java_org_eclipse_swt_internal_win32_OS_CreateFontIndirectW__Lorg_eclipse_swt_internal_win32_LOGFONTW_2@12
after_dlsym 268441660
after_dlforeach
stupid
End1: 1
stupid
End2: 1
--