getenv crashes

Posted on 2003-10-21
Last Modified: 2012-06-27
getenv function in User exit crashes when an environment variable is not exported

if ((envdbg = getenv("somevar")) != NULL )

any idea of why this is happening?

Question by:Jkrish
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LVL 45

Accepted Solution

Kdo earned 40 total points
ID: 9592253

getenv() has been around a long time so I doubt that the problem is with this particular function.

How about "proving" if the function's failure is its own doing, or caused by something else clobbering part of the program by running the following:

main (int argc, char **argv)
  char *Var;
  int    idx;

  for (idx = 1; idx < argc; idx++)
    Var = getenv (argv[idx]);
    printf (" %s = %s\n", argv[idx], Var == NULL ? "<none>" : Var);

Test it by doing something like this:

runit path
runit path terminal test nothing etc


LVL 22

Expert Comment

ID: 9592894
Perhaps you've somehow scrozzled your local copy of the environment.

Try doing this crashy line first thing in your program. If it works there but doesnt later on,
yo may have stepped on the environment.

LVL 45

Expert Comment

ID: 9593077

Hi grg99,

That's where my test code was going.  If it passes, then his program is scribbling where it aughtn't.


Author Comment

ID: 9599060
Problem is, the function is not a main function and it's an user exit
and it's more confusing because of the fact that other user exits (.pc files) are working fine.  
getenv is crashing even before it returns anything at all when the env variable is not exported.  

Thanks a lot guys!
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LVL 45

Expert Comment

ID: 9599763

Hi Jkrish,

I'm not sure what your last comment meant.

Did you try the sample code that I provided to see if getenv() has a problem.  (I still don't think that getenv() is failing on its own.)

If you've got some really good debug tools (like Rational) you should be able to discover where your program is overflowing a buffer.

If not, link the program and generate a loadmap.  Find out what's loaded right above getenv().  Chances are that a buffer one or two items above getenv() is the culprit.


Author Comment

ID: 9602886
Many thanks Kent!

I am calling a user exit (Pro*C) from oracle forms (version 6)
and this piece of function is in a library archive and it's a .pc file.

It's interesting to see if I open a text file and insert a line of text
and close prior to running the above mentioned command,
( fp = fopen("testfile","w");
everything works fine.  

Like you have pointed out, an item above the call to getenv must be a culprit. But this is the first line of code in the program (only oracle variables and host variables are declared above it).  

Thanks again
LVL 45

Expert Comment

ID: 9605756

I wonder if the Oracle library includes its own getenv() function?


Author Comment

ID: 9606013

It was because of the following

FILE *fp;

if ((envdbg = getenv("somevar")) != NULL )
// open a file pointer fp if somevar exists

if (fp)
  fprintf(fp,"print message");  <-- it's crashing here because of this
as fp was not initialized.  

FILE *fp = NULL;  // solved the problem

Thanks a lot Kent!

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