Article: Q49313
Product(s): See article
Version(s): 2.20
Operating System(s): OS/2
Keyword(s): ENDUSER | | mspl13_basic
Last Modified: 30-NOV-1989
Due to combined problems in both protected-mode CodeView (CVP) Version
2.20 and OS/2 Version 1.00 or 1.10, programs that correctly access
data files and/or system environment information could fail when
attempting this same access while running under CVP 2.20. This is
strictly a protected-mode problem and is unrelated to the use of
CodeView under MS-DOS. The sample program at the end of this article
can be used to demonstrate this problem.
The system environment information includes such items as the path and
other environment variables, as well as the current working directory
for each disk drive. This information is normally available to an
executing program, but for a program being debugged with CVP 2.20
running under OS/2 1.00 or 1.10, most of this environment information
is inaccessible.
This inaccessibility is a result of environment handling problems in
both CVP 2.20 and OS/2 Version 1.00. Since CodeView is run from the
command prompt, all the current environment information is available
to CodeView itself, but the program being debugged is given its own
new screen group in which to run. It is in this new screen group that
the current environment information is lost because it is not carried
over by either OS/2 or CodeView.
Although the OS/2 problem has been corrected in Version 1.10, the
CodeView problem still prevents access to the environment. Therefore,
upgrading either CodeView or OS/2 alone does not solve the problem.
Only with CodeView Version 2.30 running under OS/2 Version 1.10 is the
problem eliminated.
There may be some environment information available to the program
being debugged, but only if it was set in the CONFIG.SYS file at start
up. Since each new screen group is begun with a copy of the original
start-up system environment, any SET commands carried out in the
CONFIG.SYS file will then be duplicated for all subsequent screen
groups.
Otherwise, if a program needs access to environment variables that
were set in the current screen group where CodeView will be invoked,
then the only way to make the information available while debugging is
to temporarily hard code the information into the program. After
debugging, the program can be changed back to using the actual
environment strings.
The only other alternative to temporarily hard code the environment
information into the program is to set the environment variables in the
CONFIG.SYS file at boot time, rather than setting them in the current
screen group.
The only reason a file access will fail only while the program is
running under CodeView is if the program is assuming the file is in
the current working directory on the current or another drive.
If this is the case, then one of the following workarounds may be used
to gain access to files while debugging:
1. Use full pathnames for all file accesses, since this alleviates any
dependency on knowing the current working directory for the drive
that is being accessed. If it is not feasible to have hard-coded
pathnames in the completed program, at least adding the full paths
temporarily will allow debugging.
2. Put the files to be accessed in the root directory of the boot
drive. This allows them to be found even under CodeView because
with no environment information, the current working directory
defaults to the root of the boot drive.
3. Use a two-monitor debugging setup and start CodeView with the /2
option. In this situation, CVP does not need to start a new screen
group for the program being debugged because it can run it on the
second monitor. Thus, the current environment information is
available to both programs because they are both running in the
current screen group.
For more information about debugging with a two-monitor setup, query
on the following:
CodeView two monitor debugging
The following C program can be used to demonstrate this environment
problem:
Program Example:
---------------
/* TEST.C - shows inaccessible files under CodeView
Compile with : CL /Zi /Od test.c
Run with : test <filename> where <filename> is any file
in the current directory. The file will be
opened properly.
Begin CVP with : CVP test <filename> where <filename> is
the same as before. The file will not be
found when the program is run or traced.
*/
#include <stdio.h>
void main(int, char *[]);
void main(int argc, char *argv[])
{
FILE *dfile ;
if ((dfile = fopen(argv[1], "rb")) == NULL) {
perror ("") ;
printf ("Cannot open file '%s'.\n\n", argv[1]) ;
}
else {
printf("File %s opened OK.\n\n", argv[1]) ;
fclose (dfile) ;
}
}