Programming :: Pragma Pack - Local Variable Is Being Padded?
Jun 9, 2011
I am new to using 'pragma pack' and here is what I am running into :
Process A:
a.h -> defines a struct XYZ as PACKED and is of size 44bytes
a.c -> includes a.h and is able to print the size as 44 bytes.
Process B
b.c -> includes a.h,
b.c -> gets a message from process A, with struct XYZ in the message as data.
b.c -> After getting message, it is unable to print the elements of struct correctly. This is because the sizof (XYZ) in b.c is seen as 48 bytes.
I suspect, in b.c, the local variable of struct XYZ is being padded and not PACKED.
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May 23, 2011
When should I use pragma pack? I found this code on some source files while other sources do not have the pragma pack()
Code:
#pragma pack (1)
typedef struct _net_ip_header_t {
uint8 hdr_len:4;// header length
uint8 version:4;// version
uint8 tos;// type of service
uint16 tot_len;// total length
uint16 id;// identification
uint16 flags_offset;// fragment offset field
uint8 ttl;// time to live
uint8 proto;// protocol
uint16 cksum;// checksum
ip_addr src_ip;// source ip address
ip_addr dst_ip;// destination ip address
} net_ip_header_t;
#pragma pack ()
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Apr 12, 2010
I want to know is there some more efficient way of passing a pointer to a local variable as a parameter to a function in x86 asm? Right now I have to move the base pointer to a temp register, subtract from the register and pass that, like this (assuming a local var at esp-4):
Code:
mov eax, ebp
sub eax, 4
push eax
Is there a better way?
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Jul 3, 2010
It's good that GCC support intel inline disassembly syntax, but it cannot even simply address local variables/parameters properly, making itself stupid and essentially useless, look at the following:
int myfunc(float f){
int x;
float fa[8];
asm(".intel_syntax noprefix
"
"mov eax, [x]
[Code]...
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Jan 1, 2010
I know the #pragma pack(2); but how to use #pragma comment ,#pragma message , #pragma XXX .... etc..even only one example would be OK, well, let's assume the compiler is GCC, alright ? for that GCC is my favorite compiler, for a very little time i gonna use VC.
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Feb 17, 2011
how to assign a local variable value to a global variable....
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Aug 21, 2009
I'm trying to read content of file to variable and use this variable in for loop. The problem is, when I have c++ comment style in file - /*. Spaces in line are also interpreted as separated lines.
For example:
Code:
Changing $files to "$files" eliminate these problems but causes that whole content of variable is treated as one string (one execution of loop).
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Apr 7, 2010
my script has a variable which comes in the form +00.00 +0.00 -00.00 or -0.00 (the numbers can be any in that form) for any that have a + symbol I need to remove the +, but if it has a - symbol it needs to stay.
i need to make a new variable with the string from the old variable btut without any plus sign. I have tried a lot of different ways with no success, each thing I tried either left the + or removed the entire string. I think this should work but doesn't
foo=+12.40
bar=${foo#+}
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Apr 25, 2011
how I can search within a variable and assign the results to a new variable. I'll use the following as an example -
cars="Audi BMW Cadillac Chevy Dodge Ferrari Ford Mercedes"
list=`echo ${cars} | egrep -o '<A?+|<C+'`
with the echo command I get the following output assigned to list -
A
C
C
What I'd like to get for output is -
Audi
Cadillac
Chevy
how I could do this regardless of upper/lower case letters?
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Mar 30, 2011
Running into a weird issue when packing sockaddr_storage with either v4 or v6 address. To demonstrate the problem, I created a sample test program (limiting it to v4 only addresses). The problem was observed on MAC OS 10.5.8 and Linux RHEL kernel 2.6.9-42 with gcc as the compiler.
* Function packAddrs() runs a for loop packing v4 addresses into a single structure. The input address is same for every iteration, output memory size is adjusted using realloc.
* After successfully packing an address, it prints the packed structure contents using displayPackedAddrs()
* The output is fine for first two iterations. However, at the 3rd iteration, the packed contents seem to have got corrupted. It prints only the first packed address. I have tried using (malloc and memcpy) instead of realloc but no improvement.
Included below is the code and execution output.
--------Test code
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
[code]...
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Apr 28, 2010
included shell script inside c program, and i wanted to assign the value of c variable to shell variable..Can any one please suggest me how to do it?
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Oct 28, 2010
To create a weblink I needed to pad zeroes to an IP Because I couldn't find any examples I created my own.I invite anyone to improve on it and hopefully I'll see many alternatives.I'm using 'grep -o' to break down the 4 segments....
Code:
# IP=127.0.0.1
# PADIP=`echo "${IP}" | grep -o -E '([0-9]*.|[0-9]*)' | awk '{printf( "%03d
", $1)}' | tr '
' '.' | sed 's/.$//'`
# echo ${PADIP}
127.000.000.001
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Mar 17, 2011
This loop is part of a bash script which takes multiple arguments.
Code:
for ((i=1;i<=$number;++i)) ; do
offset=$(($i+5))
[code]...
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Jun 29, 2010
I have little problem with gpk servce pack (from gpk-package-extra package). When im trying to make list of my packages in system i have:
Quote:
Can't write the file, no permissions. OK, but when i run gpk service package as root, program freeze, i click create packages list option but application never create this file, status is always on 0%, even after 1 hour. I saw video tutorial, where base are created by normal user i /home - why i can't Console says nothing about this.
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Oct 4, 2010
I'm coming to emacs from Xcode. An Xcode feature I really like is the ability to type the lines#pragma mark -#pragma mark Section Heading Nameto mark the subsequent part of my code as belonging to a particular section. I can then jump to that section from a drop-down menu.Does a similar ability to break up code into named sections and to jump to a section by name exist in emacs?
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Dec 4, 2010
i want to pass variable in mysql qyery in c programming
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Feb 15, 2010
I was working my way through the steps for downloading and installing the kernel source I have done this on ever Fedora release, so this is a new error for me. The error was from yum-builddep. Here is the command and error output:
[Code]
While the symptom is a script error, I am not sure what is causing the problem.
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Jun 4, 2011
Is there some kind of universally recognized pragma that one can insert at the beginning of a text document to designate it to be UTF-8 encoded (or any other encoding)? I've seen certain editors insert encoding comments, and one or two compilers that have an encoding pragma. But I was wondering if anyone has tried to establish some kind of universal tag format for text documents.
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Mar 25, 2011
I have beat this enough and don't get what should have been a very simple thing to do. I build a variable;
Code:
CLIST=java,lua,python,php,perl,ruby,tcl
CLIST will be used by another bash script but I need to replace the commas with a space. I
[code]...
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Apr 9, 2010
How would I go about defining a variable from a document name. Example:document01.doc I want to take the 01 and set X to equal integer 1.
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Jun 2, 2010
I need to replace JAVA_OPTS= with JAVA_OPTS=<some_value>.I need to give "" value at the end of the replacement. I have tried with the following but it is not working: sed -e "s|JAVA_OPTS= |JAVA_OPTS=<some_value>"
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Jul 23, 2010
I have been searching most of today and am stuck on getting a variable into an awk portion of my bash script. I have this working:
Code:
#!/bin/sh
SRC=/var/log/mail.log
DEST=/var/www/output/myFile.txt
VAR=userName@myDomain.tld
[code]....
Can awk take a shell variable? Or do I have to do something completely different?
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Jul 1, 2010
In C++ what does the suffix, "*" mean appended to a variable type, e.g., "char* variable1;"?
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Nov 5, 2010
Following is the way I saw a variable initialized in C
Code:
static const unsigned int rtl8139_rx_config =
RxCfgRcv64K |
(RX_FIFO_THRESH << RxCfgFIFOShift) |
(RX_DMA_BURST << RxCfgDMAShift);
on following link
[URL]
I have initialized variables in past but above initialization I could not understand what is it?
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May 16, 2011
problem statement:
pattern_search="Exam Name"
sed -n "/$pattern_search/,/hello/"p tmp5 | awk '{if ( $4 != 0 && $4 ~ /[0-9]+.*[0-9]*/ ) print "$pattern_search" " " $0 }'
"tmp5" is a file. this is printing output as
$pattern_search value1
i.e value of $pattern_search is not getting substituted. i am expecting output as
Exam Name value1
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Feb 5, 2010
how shall I print each variable separately using a generalized form. I tried writing the following within a for loop...Code:echo $(echo a$(echo $i)$(echo $j))which did yield no result. So what shall I write??
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Mar 8, 2011
I have the following input:
Code:
Event 1............................................................
full_name: JENNY_JENNINGS genre: f
age: 32
[code]....
But as you can see in the input, in the 2nd "Event", the line containing "age" is not present, but in the output my code is printing the 1rst age value twice. The correct output should be blank in the age field for 2nd line in the output like this:
Code:
full_name|genre|age|code
JENNY_JENNINGS|f|32|15a
JOHN_JOHNSON|m||23c
MARY_JEAN|f|25|11d
What is wrong in my code? how can I fix it? * I�m using ubuntu 10.10
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Apr 22, 2011
How are environment variable set in tcl? I tried "set $env(MYVAR) xxxx" but it didn't work.
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Apr 14, 2011
i'm trying to execute a shell script, i'm trying to use the values in an array for use in a sed command:
sed -n '/Sales ID: ${array[$i]}/,/Totals:/p'
that command creates empty files. so my guess is that its not recognizing the array as an array but as text?
how would i be able to utilize the array in the command? i got it, didnt think that if i doubled up the single quotes that it would work, but this worked:
sed -n '/Sales ID: '${array[$i]'}/,/Totals:/p'
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Mar 25, 2011
I have a directory file capturing script, the variable is fine with in the loop but gone after the loop is done:
Code:
DIR="/usb/sdb1/media/music/"
i=1
[code]...
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