Solved

__penter and /Gh on VC++ 6.0

Posted on 2000-05-12
5
702 Views
Last Modified: 2008-03-10
I'm wondering if anyone has had any experience with the function hook system on VC++ that uses the /Gh compiler option to bung __penter calls at the beginning of each native function in an application. I'm having real trouble getting it to work.

Anyone out there that could give me a hand (and possibly a working example!) would be most appreciated..

-hd
0
Comment
Question by:Ishani
  • 3
  • 2
5 Comments
 
LVL 22

Expert Comment

by:nietod
ID: 2806754
You should be able to do something like.

void cdecl _penter(void)
{
   __asm
   {
      PUSHA ; Save all the general purpose registers.

     ; your code here.

      POPA   ; Restore all the general purpose registers.
   }
}

What is it that you want to do?  What sort of problems are you having?
0
 

Author Comment

by:Ishani
ID: 2810395
i'm not getting the linker to recognize the declaration of penter at all.

it complains of an unresolved external symbol, no matter how I declare penter or even if I write it in an external library and link it in (as the MS CAP example does)

0
 
LVL 22

Accepted Solution

by:
nietod earned 150 total points
ID: 2810914
The problem may be name decoration.  Try declarinig it as extern "C" like

extern "C" void cdecl _penter(void) ....
0
 

Author Comment

by:Ishani
ID: 2811403
spot on. although i'm still a bit puzzled:

why _penter and not __penter? even the MSDN docs show a sample implimentation as

void __cdecl __penter(void)...


what does declaring it as a C style name actually do? has this got something to do with name scambling?


thanks muchly for your help.

-hd
0
 
LVL 22

Expert Comment

by:nietod
ID: 2811612
the C compiler will add a "_" to the start of the name as part of its name decoration.  So while the linker looks for a function with two "_"'s you only specify one.

>> what does declaring it as a C style name actually do
It removes the C++ name decoration used for overloading.  this is a "code" that is appended to the end of the function name to express the parameters passed to the function.  This code is used to insure that different overloads of a particular function have unique names.
0

Featured Post

What Should I Do With This Threat Intelligence?

Are you wondering if you actually need threat intelligence? The answer is yes. We explain the basics for creating useful threat intelligence.

Join & Write a Comment

Errors will happen. It is a fact of life for the programmer. How and when errors are detected have a great impact on quality and cost of a product. It is better to detect errors at compile time, when possible and practical. Errors that make their wa…
What is C++ STL?: STL stands for Standard Template Library and is a part of standard C++ libraries. It contains many useful data structures (containers) and algorithms, which can spare you a lot of the time. Today we will look at the STL Vector. …
The goal of the video will be to teach the user the difference and consequence of passing data by value vs passing data by reference in C++. An example of passing data by value as well as an example of passing data by reference will be be given. Bot…
The viewer will learn how to user default arguments when defining functions. This method of defining functions will be contrasted with the non-default-argument of defining functions.

708 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

18 Experts available now in Live!

Get 1:1 Help Now