C Stack Corruption?

**Walter Roberson** · Nov 14 '05, 07:47 PM

Re: C Stack Corruption?

In article <1109714539.606 063.102500@f14g 2000cwb.googleg roups.com>,
Dev <dev.elope@gmai l.com> wrote:
:I'm working with some IBM sponsored C APIs to interface with a
:corporate legacy system, and it seems that I'm getting some stack
:corruption after any API call.

:I highly doubt that the IBM API is at fault, and I'm running out of
:ideas to test my code. Is it possible that it's in how I compile my
:code and link to the DLL?

It sounds to me as if you are using an API with a different calling
convention than the new code. I do not have any experience building
on Windows, so I don't know what is available, but generally speaking,
I have heard that there are at least 3 major compilers each of which
produces libraries that are incompatible with each other.

As an example of what could in theory go wrong: many years ago,
I worked with systems where the calling convention was that the
calling function had to allocate the temporary storage on the stack
to save the registers; in other systems, it is the responsibility of
the called function to do this allocation. If a calling function expected
the called function to allocate the storage but the called function
expected the called function to do it, then data above the return
address could get clobbered.
--
Rump-Titty-Titty-Tum-TAH-Tee -- Fritz Lieber

**CBFalconer** · Nov 14 '05, 07:48 PM

Re: C Stack Corruption?

Dev wrote:[color=blue]
>
> I'm working with some IBM sponsored C APIs to interface with a
> corporate legacy system, and it seems that I'm getting some stack
> corruption after any API call.
>[/color]
.... snip ...[color=blue]
>
> Unfortunately, I do not own my code, so code samples can't be
> posted. Just imagine horribly named API methods that take pointers
> to pointers to deeply nested structs of pointers. =)[/color]

System specific problems are off-topic here. c.l.c deals with the
portable C language. Dlls smells of windoze, and methods smells of
C++.

If you won't post the code you can't be helped here, and probably
not anywhere. You need to look around for suitable consultants,
who will require payment, and can be trusted with your code. Make
sure any such consultant is familiar with assembly language on your
machine. Expect to pay USD 500 to 1000 per day, plus expenses.

--
Chuck F (cbfalconer@yah oo.com) (cbfalconer@wor ldnet.att.net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home .att.net> USE worldnet address!

**Dev** · Nov 14 '05, 07:48 PM

Re: C Stack Corruption?

> System specific problems are off-topic here. c.l.c deals with the[color=blue]
> portable C language. Dlls smells of windoze, and methods smells of
> C++.[/color]

How helpful you are to inform me that no one reading comp.lang.c is
familiar with any specific system, or with cross-system and
cross-compiler complexities. Oh, whatever was I thinking?
[color=blue]
> If you won't post the code you can't be helped here, and probably
> not anywhere. You need to look around for suitable consultants,
> who will require payment, and can be trusted with your code. Make
> sure any such consultant is familiar with assembly language on your
> machine. Expect to pay USD 500 to 1000 per day, plus expenses.[/color]

I thank you, Chuck, for your condescension. My personal rates put me
at slightly over 1100 US$ a day, plus expenses. But, it's always nice
to get a reminder that other people make less.

**Dev** · Nov 14 '05, 07:48 PM

Re: C Stack Corruption?

Thanks, Fritz.

We've been looking at that as being one of the problems, but are
running into snags with the precompiled library. I appreciate the help.

**CBFalconer** · Nov 14 '05, 07:48 PM

Re: C Stack Corruption?

Dev wrote:[color=blue]
>[color=green]
>> System specific problems are off-topic here. c.l.c deals with the
>> portable C language. Dlls smells of windoze, and methods smells of
>> C++.[/color]
>
> How helpful you are to inform me that no one reading comp.lang.c is
> familiar with any specific system, or with cross-system and
> cross-compiler complexities. Oh, whatever was I thinking?[/color]

No, I informed you that it was off-topic on c.l.c and that this
newsgroup does not deal with systems specific issues. If you look
closely at what you quoted you will see the verbiage involved.
Richard Heathfield used to offer a course on "Reading for
Comprehension".

BTW, it still is off-topic.

--
"If you want to post a followup via groups.google.c om, don't use
the broken "Reply" link at the bottom of the article. Click on
"show options" at the top of the article, then click on the
"Reply" at the bottom of the article headers." - Keith Thompson

**Alan Balmer** · Nov 14 '05, 07:49 PM

Re: C Stack Corruption?

On 2 Mar 2005 06:41:42 -0800, "Dev" <dev.elope@gmai l.com> wrote:
[color=blue][color=green]
>> System specific problems are off-topic here. c.l.c deals with the
>> portable C language. Dlls smells of windoze, and methods smells of
>> C++.[/color]
>
>How helpful you are to inform me that no one reading comp.lang.c is
>familiar with any specific system, or with cross-system and
>cross-compiler complexities. Oh, whatever was I thinking?
>[/color]
I'm willing to bet that some folks who read alt.sex.bestial ity are
Windows programmers and they may be able to help you. I suggest you
post your problem there.

--
Al Balmer
Balmer Consulting
removebalmercon sultingthis@att .net

**Mark McIntyre** · Nov 14 '05, 07:49 PM

Re: C Stack Corruption?

On 2 Mar 2005 06:41:42 -0800, in comp.lang.c , "Dev" <dev.elope@gmai l.com>
wrote:
[color=blue]
>How helpful you are to inform me that no one reading comp.lang.c is
>familiar with any specific system, or with cross-system and
>cross-compiler complexities.[/color]

That wasn't what he said. He pointed out that such details are offtopic
here, and you are asking in the wrong place.
..[color=blue]
>Oh, whatever was I thinking?[/color]

about sausages?
[color=blue][color=green]
>> If you won't post the code you can't be helped here, and probably
>> not anywhere. You need to look around for suitable consultants,
>> who will require payment, and can be trusted with your code. Make
>> sure any such consultant is familiar with assembly language on your
>> machine. Expect to pay USD 500 to 1000 per day, plus expenses.[/color]
>
>I thank you, Chuck, for your condescension.[/color]

So its condescending to note that since you can't show the problem code for
commercial reasons, helping you for free is probably impossible? And its
condescending to suggest employing a consultant to do this, which
presumably is better commercially since you can bind them into an NDA? Hmm.
[color=blue]
>My personal rates put me at slightly over 1100 US$ a day, plus expenses.[/color]

Thats nice.

--
Mark McIntyre
CLC FAQ <http://www.eskimo.com/~scs/C-faq/top.html>
CLC readme: <http://www.ungerhu.com/jxh/clc.welcome.txt >

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**Gordon Burditt** · Nov 14 '05, 07:49 PM

Re: C Stack Corruption?

>I'm working with some IBM sponsored C APIs to interface with a[color=blue]
>corporate legacy system, and it seems that I'm getting some stack
>corruption after any API call.[/color]

There is no guarantee that you can mix the outputs of two different
compilers together, particularly if they use different linkage
conventions for passing and retrieving arguments. In the worst
case, one compiler won't even recognize the other's object code as
object code. You don't seem to have that problem, but stuff like
how stuff gets pushed on the stack (or put in registers), where to
look for return values of various types, which registers are saved
or trashed across function calls, etc. may be an issue.

One possibility to consider is a "glue" routine, written in assembly
language. It accepts a call from one compiler module, re-arranges
the arguments the way the other module wants it, then accepts back
a return value and passes it back to the first compiler modules.
You might need a lot of "glue" routines here: possibly one per
function on either side.

[color=blue]
>I believe the APIs were designed to be used with IBM VisualAge, but I'm
>compiling my program with both gcc/cygwin and Microsoft's Visual C++
>compiler. While running I actually get different behavior with each
>compiler. To link to the library with cl.exe I generated a .lib file
>from the .dll file using a small open source application (script) which
>I can't seem to find online anymore (google reindex?).
>
>I can get the program to continue to run for a while by adding a char
>x[10000]; buffer as the last local variable in my function, but
>eventually I get a core dump. Stepping through the application in gdb
>I see my char buffer x go from '\0' (repeats 9999 times) to garbage
>values after any IBM API call. Commenting out x yields an immediate
>crash at best, or overwrites other necessary local variables which
>wreaks bloody havoc on subsequent calls.[/color]

One screwup I've seen with stack imbalance on gcc happens when the
function thinks it's returning a double but the caller thinks it's
returning int. Blam! floating point unit stack overflow. The real
problem here is the code is broken (and it could be fixed by putting
a declaration in a header file and using it where needed). I think I've
seen a case where the C stack got trashed, but I don't remember the
situation. Again, bad code, most likely caller and callee not agreeing
on the types of stuff.

Warnings like those produced by gcc -Wall are your friend. Try
fixing these first, especially those that say "implicit declaration
of function ______".
[color=blue]
>I've checked and double checked the parameters going into and coming
>out of the API calls, and they appear to be correct. I've also
>initialized all local variables.
>
>I highly doubt that the IBM API is at fault, and I'm running out of
>ideas to test my code.[/color]

If you're using two different APIs on the calling and called side,
that's probably a mistake, whether or not either API is "wrong",
whatever that means.
[color=blue]
>Is it possible that it's in how I compile my
>code and link to the DLL? This is running as JNI code for a larger
>Java application, so I'm using ANT to build (the behavior still
>exhibits itself when all JNI code is removed and the program is run as
>a c console application). Below are my build targets.[/color]

If possible, try compiling with the same compiler as the proprietary
dll.
[color=blue]
>Does anyone have any further suggestions for debugging a gcc compiled
>application linked to a proprietary dll in Windows? Is there any way
>to get an easy printout of the stack at any given point in time?
>
>Unfortunatel y, I do not own my code, so code samples can't be posted.
>Just imagine horribly named API methods that take pointers to pointers
>to deeply nested structs of pointers. =)
>
>All help is greatly appreciated. My coworkers and I are starting to
>bang our heads against the wall.[/color]

You're probably not going to get much useful help if you can't show
us the code. I can only speculate in generalities, which roughly
comes down to "undefined behavior -> shit happens".

Gordon L. Burditt

**Dev** · Nov 14 '05, 07:50 PM

Re: C Stack Corruption?

> No, I informed you that it was off-topic on c.l.c and that this[color=blue]
> newsgroup does not deal with systems specific issues. If you look
> closely at what you quoted you will see the verbiage involved.
> Richard Heathfield used to offer a course on "Reading for
> Comprehension".[/color]

Are you familiar with the advanced course, "Reading for Comprehension
of Subtext?"

**Dev** · Nov 14 '05, 07:50 PM

Re: C Stack Corruption?

Thanks, Gordon, you and Walter gave me enough to go on to actually find
the problem.

Turns out it was in calling conventions and an incorrect header file.
The header file was defining everything as using Pascal calling
conventions whereas the library was actually compiled to use standard
calling conventions.

That'll fry a stack real fast.

Dev

**Dev** · Nov 14 '05, 07:50 PM

Re: C Stack Corruption?

I'm thankful that I have better things to do than bicker with people
who obviously don't.

Cheers, mates. Thanks to those who tried to help. Looks like this
wasn't such a horrible place to look for help, after all.

**Mark McIntyre** · Nov 14 '05, 07:51 PM

Re: C Stack Corruption?

On 3 Mar 2005 10:14:52 -0800, in comp.lang.c , "Dev" <dev.elope@gmai l.com>
wrote:
[color=blue][color=green]
>> No, I informed you that it was off-topic on c.l.c and that this
>> newsgroup does not deal with systems specific issues. If you look
>> closely at what you quoted you will see the verbiage involved.
>> Richard Heathfield used to offer a course on "Reading for
>> Comprehension".[/color]
>
>Are you familiar with the advanced course, "Reading for Comprehension
>of Subtext?"[/color]

Perhaps, if you want help on a topical subject, you'd find it more
appropriate to post your request in the text, and leave the subtext alone?

--
Mark McIntyre
CLC FAQ <http://www.eskimo.com/~scs/C-faq/top.html>
CLC readme: <http://www.ungerhu.com/jxh/clc.welcome.txt >

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**Mark McIntyre** · Nov 14 '05, 07:51 PM

Re: C Stack Corruption?

On 3 Mar 2005 10:37:52 -0800, in comp.lang.c , "Dev" <dev.elope@gmai l.com>
wrote:
[color=blue]
>Turns out it was in calling conventions and an incorrect header file.
>The header file was defining everything as using Pascal calling
>conventions whereas the library was actually compiled to use standard
>calling conventions.[/color]

And all of this is offtopic here. Please don't consider the fact that you
got help this time as an indication that you should come back and ask more
offtopic stuff.
[color=blue]
>That'll fry a stack real fast.[/color]

not as fast as the flames would fry ...
--
Mark McIntyre
CLC FAQ <http://www.eskimo.com/~scs/C-faq/top.html>
CLC readme: <http://www.ungerhu.com/jxh/clc.welcome.txt >

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**Dev** · Nov 14 '05, 07:51 PM

Re: C Stack Corruption?

> And all of this is offtopic here. Please don't consider the fact that
you[color=blue]
> got help this time as an indication that you should come back and ask[/color]
more[color=blue]
> offtopic stuff.[/color]

Good thing it's an unmoderated newsgroup and I can post all the
offtopic stuff I want, limited solely by my frustration at replies from
people like you. But, thankfully, I have a very high tolerance. =)

Speaking of offtopic, would it be inappropriate for me to test my
script that posts hourly news updates on comp.lang.c?