Problem with putenv() in global constructor

Problem with putenv() in global constructor

[Gregory Shpitalnik]

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Hi !

I found some strange putenv() function behavior when it's used in a
global object (C++ code).
constructor. I work on SPARC/Solaris 8 with g++/gcc version 2.95.3
20010315 (release).
Below is the C++ program that sets new (not existed yet) environment
variable MYPATH
with the help of putenv() C-function in the global object constructor.
It turned out that:
1. This environment variable setting is invisible within the main()
function
2. Resetting of this environment variable in the main() function causes
"freeing of non heap memory - attempting to free memory on the stack"
problem
(this is the message from Rational purify tool) within putenv() function
and
does not change the environment variable.
It seems that something goes wrong within the data structure
that hold environment variables.

I compiled the program with "g++ -Wall test.cpp -o test".
------------------------------------------
// test.cpp

#include <iostream.h>
#include <stdio.h>
#include <stdlib.h>


static const char* env_var = "MYPATH";

class MyClass
{
public:
     MyClass()
     {
           cout << env_var << " = " << getenv(env_var) << endl;
           char* value = (char*) malloc(100);
           strcpy(value, "MYPATH=/tmp:/users/gregory");
           putenv(value);
           cout << env_var << " = " << getenv(env_var) << endl;
     }
};

MyClass a;

int main(int argc, char *argv[])
{
  cout << env_var << " = " << getenv(env_var) << endl;
  char* value = (char*) malloc(100);
  strcpy(value, "MYPATH=gregory");
  putenv(value);
  cout << env_var << " = " << getenv(env_var) << endl;

  return 0;
}
-------------------------------------------
The output of the program is:
-----------------------------
MYPATH = (null)
MYPATH = /tmp:/users/galileo101/gregory
MYPATH = (null)
MYPATH = (null)
-----------------------------

Is it a known problem ? Is it a feature or a bug ?

Thanks,

Gregory Shpitalnik
gregory@il.marvell.com


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Problem with putenv() in global constructor

[Gregory Shpitalnik]

[-- Attachment #1: Type: text/plain, Size: 1922 bytes --]

Hi !

I found some strange putenv() function behavior when it's used in a
global object (C++ code).
constructor. I work on SPARC/Solaris 8 with g++/gcc version 2.95.3
20010315 (release).
Below is the C++ program that sets new (not existed yet) environment
variable MYPATH
with the help of putenv() C-function in the global object constructor.
It turned out that:
1. This environment variable setting is invisible within the main()
function
2. Resetting of this environment variable in the main() function causes
"freeing of non heap memory - attempting to free memory on the stack"
problem
(this is the message from Rational purify tool) within putenv() function
and
does not change the environment variable.
It seems that something goes wrong within the data structure
that hold environment variables.

I compiled the program with "g++ -Wall test.cpp -o test".
------------------------------------------
// test.cpp

#include <iostream.h>
#include <stdio.h>
#include <stdlib.h>


static const char* env_var = "MYPATH";

class MyClass
{
public:
     MyClass()
     {
           cout << env_var << " = " << getenv(env_var) << endl;
           char* value = (char*) malloc(100);
           strcpy(value, "MYPATH=/tmp:/users/gregory");
           putenv(value);
           cout << env_var << " = " << getenv(env_var) << endl;
     }
};

MyClass a;

int main(int argc, char *argv[])
{
  cout << env_var << " = " << getenv(env_var) << endl;
  char* value = (char*) malloc(100);
  strcpy(value, "MYPATH=gregory");
  putenv(value);
  cout << env_var << " = " << getenv(env_var) << endl;

  return 0;
}
-------------------------------------------
The output of the program is:
-----------------------------
MYPATH = (null)
MYPATH = /tmp:/users/galileo101/gregory
MYPATH = (null)
MYPATH = (null)
-----------------------------

Is it a known problem ? Is it a feature or a bug ?

Thanks,

Gregory Shpitalnik
gregory@il.marvell.com


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n:Shpitalnik;Gregory
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adr:;;;;;;
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email;internet:gregory@il.marvell.com
x-mozilla-cpt:;0
fn:Gregory Shpitalnik
end:vcard

Re: Problem with putenv() in global constructor

[Alexandre Oliva]

On Jan  7, 2003, Gregory Shpitalnik <gregory@il.marvell.com> wrote:

> I found some strange putenv() function behavior when it's used in a
> global object (C++ code).
> constructor. I work on SPARC/Solaris 8 with g++/gcc version 2.95.3
> 20010315 (release).

Well, then you're probably going to have to discuss this with Sun
engineers who wrote their C library.  putenv() is not implemented in
GCC, GCC just uses whatever the C library of the OS you're running
has to offer.

-- 
Alexandre Oliva   Enjoy Guarana', see http://www.ic.unicamp.br/~oliva/
Red Hat GCC Developer                 aoliva@{redhat.com, gcc.gnu.org}
CS PhD student at IC-Unicamp        oliva@{lsd.ic.unicamp.br, gnu.org}
Free Software Evangelist                Professional serial bug killer

Re: Problem with putenv() in global constructor

[Alexandre Oliva]

On Jan  7, 2003, Gregory Shpitalnik <gregory@il.marvell.com> wrote:

> I found some strange putenv() function behavior when it's used in a
> global object (C++ code).
> constructor. I work on SPARC/Solaris 8 with g++/gcc version 2.95.3
> 20010315 (release).

Well, then you're probably going to have to discuss this with Sun
engineers who wrote their C library.  putenv() is not implemented in
GCC, GCC just uses whatever the C library of the OS you're running
has to offer.

-- 
Alexandre Oliva   Enjoy Guarana', see http://www.ic.unicamp.br/~oliva/
Red Hat GCC Developer                 aoliva@{redhat.com, gcc.gnu.org}
CS PhD student at IC-Unicamp        oliva@{lsd.ic.unicamp.br, gnu.org}
Free Software Evangelist                Professional serial bug killer