Originally posted by: SystemAdmin

When I debug C-language in AIX system and use dbx command to debug it, I attent to execute the follow sentence:
(dbx) assign errno = 1
but system prints an error message:
incompatible types
I don't know what the problem is,probably in the status of debugging the variable of errno coundn't be changed value or other causes.
Please tell me, thank you!
#AIX-Forum

Originally posted by: nagger

OK I have the same issue - I think it is because errno is actually defined in the C runtime environment and not really in your program but we can access errno via address as below:

(dbx) print errno
0

(dbx) type errno
&errno = 0x2ff22ff8
(dbx) assign 0x2ff22ff8 = 1

(dbx) print errno
1

Hope that elps, N
#AIX-Forum

Originally posted by: SystemAdmin

Thank you very much!
I have practised your method and succeeded.
Thank you!
This forum is very good and there are many experts in every fields. Their technic is
perfect and they are enthusiasm.
Since I have some difficout question I will be here to appear. If I know which somebody needs I can try my best!
#AIX-Forum

Originally posted by: SystemAdmin

Thank you very much!
I have practised your method and succeeded.
Thank you!
This forum is very good and there are many experts in every fields. Their technic is
perfect and they are enthusiasm.
Since I have some difficout question I will be here to appear. If I know which somebody needs I can try my best!
#AIX-Forum

Originally posted by: SystemAdmin

I'm be very appreciated for your help.
I practised a function named "int main()" using your method, and it is successful.
But, now I changed the function' name to any other such as "int Test()", using the "int main()" function called it. I also used your method:
1)(dbx) type errno
&errno = 0x2ff22ff8
2)(dbx) assign 0x2ff22ff8 = 1
3)(dbx) print errno
1
errno's value is actually 1, but I go on debugging
4))(dbx) n
the program didn't execute according to my imagine and I an other time to print the value of errno, I finded that it was 0, I didn't know why its value coundn't be really changed?
5) (dbx) print errno
0
please help me!

If you can use Attach Files to test it I can't be thankful enough to
#AIX-Forum

Originally posted by: dickdunbar

One thing you might try is to get a compiler listing.
errno is a global value in a non-threaded program,
because there is normally only one system call which
manipulates it.

In a threaded program, where there can be multiple system calls
being executed from different threads, errno has to change.

It is the compiler that changes this. Compare test.lst
files created with these two commands:

xlc -qsource test.c # non-threaded
xlc_r -qsource test.c # threaded

The threaded listing will show what errno gets expanded to; eg.,

11 | if(errno) {
11 + if((*_Errno())) {

The source "errno" was converted (by the header file) to
a function call ... which retrieves the thread specific errno.
#AIX-Forum