Q46851: Calling C Function That Uses getenv() Doesn’t Work

Article: Q46851
Product(s): See article
Version(s): 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | SR# S890601-20 B_BasicCom S_C S_QuickC | mspl13_basic
Last Modified: 28-DEC-1989

When a compiled BASIC program CALLs a C function that uses the
getenv() function, no path is returned from getenv(). The getenv()
function in C uses the ENVIRON variable to access the environment
table. The ENVIRON variable is an array of pointers to the strings
that constitute the process environment. This variable is initialized
by the C start-up code. Since the C function is CALLed from the BASIC
program, the C start-up code is not executed; therefore, the ENVIRON
variable is not initialized (it is NUL by default).

To work around this problem, use the ENVIRON$ function in the BASIC
program and pass the desired path to the C function.

This information applies to Microsoft QuickBASIC Versions 4.00, 4.00b,
and 4.50; to Microsoft BASIC Compiler Versions 6.00 and 6.00b; to
Microsoft BASIC PDS Version 7.00; to Microsoft QuickC Compiler
Versions 1.00, 1.01, 2.00, 2.01; and to Microsoft C Compiler Versions
5.00 and 5.10.

Code Example
------------

The following are the BASIC and C source files that demonstrate that
CALLing a C function that uses the getenv() function returns a NUL
ENVIRON variable:

' BASIC Source Code:
DECLARE SUB EnvironTest CDECL ()
CLS
CALL EnvironTest
END

/* C source code: */
#include <stdlib.h>
#include <stdio.h>
void EnvironTest(void)
{
  char *temp;
  temp = getenv( "PATH" );
  printf( "Path: %s\nenviron: %x\n", temp, environ );
}

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