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Re: Empty IAT entry

On Thu, 15 Jul 2004 15:40:03 +0100, Nick Clifton <> wrote:
(Sorry for the long delay in replying to your email)

No dramas. I appreciate the reply...

For which target ? Using what command line ? Can you include the simple C program so that we can reproduce the problem ourselves ?

I am using "gcc (GCC) 3.3.1 (cygming special)" on Windows 2000 with no specified target (so I guess that defaults to i686-pc-cygwin). A simple example that repeats the problem is shown below (blah.c). The command line I used to compile the sample program is: gcc blah.c

#include <stdio.h>
int main(int argc, char **argv)
	printf("hi there");

objdump -x a.exe reports:

The Data Directory
Entry 0 00000000 00000000 Export Directory [.edata (or where ever we found it)]
Entry 1 00004000 000001ec Import Directory [parts of .idata]
Entry 2 00000000 00000000 Resource Directory [.rsrc]
Entry 3 00000000 00000000 Exception Directory [.pdata]
Entry 4 00000000 00000000 Security Directory
Entry 5 00000000 00000000 Base Relocation Directory [.reloc]
Entry 6 00000000 00000000 Debug Directory
Entry 7 00000000 00000000 Description Directory
Entry 8 00000000 00000000 Special Directory
Entry 9 00000000 00000000 Thread Storage Directory [.tls]
Entry a 00000000 00000000 Load Configuration Directory
Entry b 00000000 00000000 Bound Import Directory
Entry c 00000000 00000000 Import Address Table Directory
Entry d 00000000 00000000 Delay Import Directory
Entry e 00000000 00000000 Reserved
Entry f 00000000 00000000 Reserved

There is an import table in .idata at 0x404000

The Import Tables (interpreted .idata section contents)
 vma:            Hint    Time      Forward  DLL       First
                 Table   Stamp     Chain    Name      Thunk
 00004000	00004040 00000000 00000000 000041c0 00004088

There is definitely an import table that contains perfectly valid IAT entries, but for some reason the first thunk isn't populated in the Data Directory. Interestingly this example program compiles and executes just perfectly under Windows, so it is may not be a bug. Presumably the WinXX PE loader is smart enough to manually traverse the import table until it finds the first thunk.

The reason I stumbled onto this is that I am writing a development kit for the XBOX. The XBOX executes plain old PE files (albeit with a slightly modified header). However, the XBOX PE loader apparently doesn't behave the same as its WinXX counterpart, and it expects the value to be populated in the header.

In the end, I got around this by post-processing the generated EXE, doing the manual traversal myself, and getting the value directly.

Craig Edwards

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