Application behaving in 3 different ways on 3 different machines Post: 302752731

Sponsored Content

Top Forums Programming Application behaving in 3 different ways on 3 different machines Post 302752731 by jim mcnamara on Monday 7th of January 2013 12:36:47 PM

01-07-2013

Registered User

There is a set of standards for C. They dictate what will or will not happen in the language.

Doing what you did created something that has undefined behavior. I'll make one pass at this.
When you run a C program:

Code:

1 - the OS  creates a stack frame for main.
2 - the os simply overlays that stack on top of existing garbage in memory
3 - it does this for efficiency reasons and because that memory is no longer part of any process.
4 - when your program ran,  those pointers were parked on top of memory that had some existing values in it.
5 - what was in the memory depends on the program that lived in that exact memory before
6 - it could be all 00000000, it could literally be anything.
7 - since it could be anything, it is possible that the memory pointed to (0xfaaa0000) - let's pretend.
8 - 0xfaaa0000 just HAPPENED to be by random chance an OS allocated  location on your existing stack frame.
9 - Now we can use the memory for our program - no crash.
10 Why? because the memory is part of the process so you can what you want to it
11 What if 0xfaaa0000 was NOT part of allocated memory?  Boom, program crash.
12 Therefore there is no known way to predict the behavior of the code, it is undefined

jim mcnamara

View Public Profile for jim mcnamara

Find all posts by jim mcnamara

9 More Discussions You Might Find Interesting

1. UNIX for Advanced & Expert Users

ftp application behaving erratically

Hi, I am working on a custom made FTP application. The application is behaving erratically for the "ls" command. Wild card character passed to the "ls" command (like "ls *temp") is giving inconsistent results. On debuggin I have found that the "ls" command is implemented as shown below in the...

2. UNIX for Advanced & Expert Users

csplit not behaving

I have a large file with the first 2 characters of each line determining the type of record. type 03 being a subheader and then it will have multiple 04 records. eg: 03,xxx,xxxx,xxxx 04,xxxxxxxxxxxxxxxxxxxxxxxxxxxx 04,xxxxxxxxxxxxxxxxxxxxxxxxxxxx 03,xxx,xxx,xxx ...

3. Red Hat

application to be run on machines connected in same network

I have a set up of 5 machines which are connected in same network. Now i want to run a small application so that those machines are not ideal.

4. Shell Programming and Scripting

tr command behaving unexpectedly

Im trying to execute the below command on our server to list files and replace the newline in the file list with spaces, but the character 'n' is getting replaced with a space, is there any environment variable that needs to be set in UNIX? sh -c 'ls -trx...

5. UNIX for Advanced & Expert Users

FTP behaving erraneous way

Hi Gurus, I tried FTP one file to UNIX which got values like wel^come If I see the content in unix, it shows like wel^Zcome ^ coverted into ^Z (Control + Z ) Can someone please share what is happening here? Thanks, Shahnaz

6. Red Hat

nslookup behaving strangely

I have two servers on same domain. one can nslookup other cannot Psu100 can lookup to psu000, psu010 & psu011 Psu110 can NOT lookup to psu000, psu010 & psu011 I verified resolv.conf entries on both psu000 and psu010 and it contains both name servers (10.200.10.21 & 10.200.11.22).I am...

7. UNIX and Linux Applications

Linux application upgrade ways

Hello. I need upgrade memcached. This software is installed throuth yum. In official repositories isn`t newest version of memcached, but this one is vulnerable. So looks like I need built it from source, but I dont really want to install c libraries un compilers on system. 1.) So can I compile...

8. Shell Programming and Scripting

awk not behaving as expected

Hi, Immediate help on below will be appreciated. I have to read a file (max of 10MB) which will have no new line characters, i.e. data in single line. and have to inster '\n' at every 100 characters. and if record starts with 'BUCA' then need to pick value of length 10 at position 71 and...

9. UNIX for Advanced & Expert Users

[Solved] wc behaving weirdly

Can anyone explain why wc is behaving weirdly? Their are only 2 occurrences but wc thinks their are 7 occurrences. I have even manually checked this. $ grep -i base * lit: base xx lit.lst:003- 00103 BASE XX $ grep -i base * | wc -w ...

LEARN ABOUT SUSE

holidays

holidays(4)							   File Formats 						       holidays(4)

NAME

       holidays - prime/nonprime table for the accounting system

SYNOPSIS

       /etc/acct/holidays

DESCRIPTION

       The   /etc/acct/holidays file describes which hours are considered prime time and which days  are holidays.  Holidays and weekends are con-
       sidered non-prime time hours.  /etc/acct/holidays is used by the accounting system.

       All lines beginning with an "*" are comments.

       The  /etc/acct/holidays file consists of two sections.  The first non-comment line defines the current year and the start time of prime and
       non-prime time hours, in the form:

       current_year	 prime_start	  non_prime_start

       The remaining non-comment lines define the holidays in the  form:

       month/day     company_holiday

       Of these two fields, only the  month/day is actually used by  the accounting system programs.

       The  /etc/acct/holidays file must be updated each year.

EXAMPLES

       Example 1: Example of the /etc/acct/holidays file.

       The following is an example of the /etc/acct/holidays file:

       * Prime/Nonprime Table for the accounting system
       *
       * Curr	  Prime     Non-Prime
       * Year	  Start     Start
       *
	 1991	  0830	   1800
       *
       * only the first column (month/day) is significant.
       *
       * month/day    Company Holiday
       *
	 1/1	      New Years Day
	 5/30	      Memorial Day
	 7/4	      Indep. Day
	 9/5	      Labor Day
	 11/24	      Thanksgiving Day
	 11/25	      day after Thanksgiving
	 12/25	      Christmas
	 12/26	      day after Christmas

SEE ALSO

       acct(1M)

SunOS 5.10							    28 Mar 1991 						       holidays(4)