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• How to port a simple application (which uses only stadard libc) to iPhone OS ?

  - by psihodelia

  There is a simple application written in C, which uses only standard C library functions (from stdio, stdlib, etc.) and Makefile+GCC to build it. Now, I wanna port it to iPhone OS for iPhone/iPads. Will it be seamless or are there any possible incompatibility issues?

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• Why is this C program giving a wrong output?

  - by JMSA

  Why is this C program giving a wrong output? #include<stdio.h> void main() { float f = 12345.054321; printf("%f", f); getch(); } Output: 12345.054688 But the output should be, 12345.054321. I am using VC++ in VS2008.

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• Weird initialization in C

  - by pacopepe

  Hi there, I have this piece of code and i don't know how it works #include <stdio.h> int main(void) { int numero = ({const int i = 10; i+10;}); printf("%d\n", numero); // Prints 20 return 0; } Why if i delete the second part (i+10;), the compiler gets an error? Why are the brackets necessary? Thank you ^^!

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• Parent Objects

  - by Ali Bahrami

  Support for Parent Objects was added in Solaris 11 Update 1. The following material is adapted from the PSARC arc case, and the Solaris Linker and Libraries Manual. A "plugin" is a shared object, usually loaded via dlopen(), that is used by a program in order to allow the end user to add functionality to the program. Examples of plugins include those used by web browsers (flash, acrobat, etc), as well as mdb and elfedit modules. The object that loads the plugin at runtime is called the "parent object". Unlike most object dependencies, the parent is not identified by name, but by its status as the object doing the load. Historically, building a good plugin is has been more complicated than it should be: A parent and its plugin usually share a 2-way dependency: The plugin provides one or more routines for the parent to call, and the parent supplies support routines for use by the plugin for things like memory allocation and error reporting. It is a best practice to build all objects, including plugins, with the -z defs option, in order to ensure that the object specifies all of its dependencies, and is self contained. However: The parent is usually an executable, which cannot be linked to via the usual library mechanisms provided by the link editor. Even if the parent is a shared object, which could be a normal library dependency to the plugin, it may be desirable to build plugins that can be used by more than one parent, in which case embedding a dependency NEEDED entry for one of the parents is undesirable. The usual way to build a high quality plugin with -z defs uses a special mapfile provided by the parent. This mapfile defines the parent routines, specifying the PARENT attribute (see example below). This works, but is inconvenient, and error prone. The symbol table in the parent already describes what it makes available to plugins — ideally the plugin would obtain that information directly rather than from a separate mapfile. The new -z parent option to ld allows a plugin to link to the parent and access the parent symbol table. This differs from a typical dependency: No NEEDED record is created. The relationship is recorded as a logical connection to the parent, rather than as an explicit object name However, it operates in the same manner as any other dependency in terms of making symbols available to the plugin. When the -z parent option is used, the link-editor records the basename of the parent object in the dynamic section, using the new tag DT_SUNW_PARENT. This is an informational tag, which is not used by the runtime linker to locate the parent, but which is available for diagnostic purposes. The ld(1) manpage documentation for the -z parent option is: -z parent=object Specifies a "parent object", which can be an executable or shared object, against which to link the output object. This option is typically used when creating "plugin" shared objects intended to be loaded by an executable at runtime via the dlopen() function. The symbol table from the parent object is used to satisfy references from the plugin object. The use of the -z parent option makes symbols from the object calling dlopen() available to the plugin. Example For this example, we use a main program, and a plugin. The parent provides a function named parent_callback() for the plugin to call. The plugin provides a function named plugin_func() to the parent: % cat main.c #include <stdio.h> #include <dlfcn.h> #include <link.h> void parent_callback(void) { printf("plugin_func() has called parent_callback()\n"); } int main(int argc, char **argv) { typedef void plugin_func_t(void); void *hdl; plugin_func_t *plugin_func; if (argc != 2) { fprintf(stderr, "usage: main plugin\n"); return (1); } if ((hdl = dlopen(argv[1], RTLD_LAZY)) == NULL) { fprintf(stderr, "unable to load plugin: %s\n", dlerror()); return (1); } plugin_func = (plugin_func_t *) dlsym(hdl, "plugin_func"); if (plugin_func == NULL) { fprintf(stderr, "unable to find plugin_func: %s\n", dlerror()); return (1); } (*plugin_func)(); return (0); } % cat plugin.c #include <stdio.h> extern void parent_callback(void); void plugin_func(void) { printf("parent has called plugin_func() from plugin.so\n"); parent_callback(); } Building this in the traditional manner, without -zdefs: % cc -o main main.c % cc -G -o plugin.so plugin.c % ./main ./plugin.so parent has called plugin_func() from plugin.so plugin_func() has called parent_callback() As noted above, when building any shared object, the -z defs option is recommended, in order to ensure that the object is self contained and specifies all of its dependencies. However, the use of -z defs prevents the plugin object from linking due to the unsatisfied symbol from the parent object: % cc -zdefs -G -o plugin.so plugin.c Undefined first referenced symbol in file parent_callback plugin.o ld: fatal: symbol referencing errors. No output written to plugin.so A mapfile can be used to specify to ld that the parent_callback symbol is supplied by the parent object. % cat plugin.mapfile $mapfile_version 2 SYMBOL_SCOPE { global: parent_callback { FLAGS = PARENT }; }; % cc -zdefs -Mplugin.mapfile -G -o plugin.so plugin.c However, the -z parent option to ld is the most direct solution to this problem, allowing the plugin to actually link against the parent object, and obtain the available symbols from it. An added benefit of using -z parent instead of a mapfile, is that the name of the parent object is recorded in the dynamic section of the plugin, and can be displayed by the file utility: % cc -zdefs -zparent=main -G -o plugin.so plugin.c % elfdump -d plugin.so | grep PARENT [0] SUNW_PARENT 0xcc main % file plugin.so plugin.so: ELF 32-bit LSB dynamic lib 80386 Version 1, parent main, dynamically linked, not stripped % ./main ./plugin.so parent has called plugin_func() from plugin.so plugin_func() has called parent_callback() We can also observe this in elfedit plugins on Solaris systems running Solaris 11 Update 1 or newer: % file /usr/lib/elfedit/dyn.so /usr/lib/elfedit/dyn.so: ELF 32-bit LSB dynamic lib 80386 Version 1, parent elfedit, dynamically linked, not stripped, no debugging information available Related Other Work The GNU ld has an option named --just-symbols that can be used in a similar manner: --just-symbols=filename Read symbol names and their addresses from filename, but do not relocate it or include it in the output. This allows your output file to refer symbolically to absolute locations of memory defined in other programs. You may use this option more than once. -z parent is a higher level operation aimed specifically at simplifying the construction of high quality plugins. Although it employs the same operation, it differs from --just symbols in 2 significant ways: There can only be one parent. The parent is recorded in the created object, and can be displayed by 'file', or other similar tools.

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• HAProxy: Display a "BADREQ" | BADREQ's by the thousands

  - by GruffTech

  My HAProxy Configuration. #HA-Proxy version 1.3.22 2009/10/14 Copyright 2000-2009 Willy Tarreau <[email protected]> global maxconn 10000 spread-checks 50 user haproxy group haproxy daemon stats socket /tmp/haproxy log localhost local0 log localhost local1 notice defaults mode http maxconn 50000 timeout client 10000 option forwardfor except 127.0.0.1 option httpclose option httplog listen dcaustin 0.0.0.0:80 mode http timeout connect 12000 timeout server 60000 timeout queue 120000 balance roundrobin option httpchk GET /index.html log global option httplog option dontlog-normal server web1 10.10.10.101:80 maxconn 300 check fall 1 server web2 10.10.10.102:80 maxconn 300 check fall 1 server web3 10.10.10.103:80 maxconn 300 check fall 1 server web4 10.10.10.104:80 maxconn 300 check fall 1 listen stats 0.0.0.0:9000 mode http balance log global timeout client 5000 timeout connect 4000 timeout server 30000 stats uri /haproxy HAProxy is running, and the socket is working... adam@dcaustin:/etc/haproxy# echo "show info" | socat stdio /tmp/haproxy Name: HAProxy Version: 1.3.22 Release_date: 2009/10/14 Nbproc: 1 Process_num: 1 Pid: 6320 Uptime: 0d 0h14m58s Uptime_sec: 898 Memmax_MB: 0 Ulimit-n: 20017 Maxsock: 20017 Maxconn: 10000 Maxpipes: 0 CurrConns: 47 PipesUsed: 0 PipesFree: 0 Tasks: 51 Run_queue: 1 node: dcaustin desiption: Errors show nothing from socket... adam@dcaustin:/etc/haproxy# echo "show errors" | socat stdio /tmp/haproxy adam@dcaustin:/etc/haproxy# However... My Error log is exploding with "badrequests" with the Error code cR. cR (according to 1.3 documentation) is The "timeout http-request" stroke before the client sent a full HTTP request. This is sometimes caused by too large TCP MSS values on the client side for PPPoE networks which cannot transport full-sized packets, or by clients sending requests by hand and not typing fast enough, or forgetting to enter the empty line at the end of the request. The HTTP status code is likely a 408 here. Correct on the 408, but we're getting literally thousands of these requests every hour. (This log snippet is an clip for about 10 seconds of time...) Jun 30 11:08:52 localhost haproxy[6320]: 92.22.213.32:26448 [30/Jun/2011:11:08:42.384] dcaustin dcaustin/<NOSRV> -1/-1/-1/-1/10002 408 212 - - cR-- 35/35/18/0/0 0/0 "<BADREQ>" Jun 30 11:08:54 localhost haproxy[6320]: 71.62.130.24:62818 [30/Jun/2011:11:08:44.457] dcaustin dcaustin/<NOSRV> -1/-1/-1/-1/10001 408 212 - - cR-- 39/39/16/0/0 0/0 "<BADREQ>" Jun 30 11:08:55 localhost haproxy[6320]: 84.73.75.236:3589 [30/Jun/2011:11:08:45.021] dcaustin dcaustin/<NOSRV> -1/-1/-1/-1/10008 408 212 - - cR-- 35/35/15/0/0 0/0 "<BADREQ>" Jun 30 11:08:55 localhost haproxy[6320]: 69.39.20.190:49969 [30/Jun/2011:11:08:45.709] dcaustin dcaustin/<NOSRV> -1/-1/-1/-1/10000 408 212 - - cR-- 37/37/16/0/0 0/0 "<BADREQ>" Jun 30 11:08:56 localhost haproxy[6320]: 2.29.0.9:58772 [30/Jun/2011:11:08:46.846] dcaustin dcaustin/<NOSRV> -1/-1/-1/-1/10001 408 212 - - cR-- 43/43/22/0/0 0/0 "<BADREQ>" Jun 30 11:08:57 localhost haproxy[6320]: 212.139.250.242:57537 [30/Jun/2011:11:08:47.568] dcaustin dcaustin/<NOSRV> -1/-1/-1/-1/10000 408 212 - - cR-- 42/42/21/0/0 0/0 "<BADREQ>" Jun 30 11:08:58 localhost haproxy[6320]: 74.79.195.75:55046 [30/Jun/2011:11:08:48.559] dcaustin dcaustin/<NOSRV> -1/-1/-1/-1/10000 408 212 - - cR-- 46/46/24/0/0 0/0 "<BADREQ>" Jun 30 11:08:58 localhost haproxy[6320]: 74.79.195.75:55044 [30/Jun/2011:11:08:48.554] dcaustin dcaustin/<NOSRV> -1/-1/-1/-1/10004 408 212 - - cR-- 45/45/24/0/0 0/0 "<BADREQ>" Jun 30 11:08:58 localhost haproxy[6320]: 74.79.195.75:55045 [30/Jun/2011:11:08:48.554] dcaustin dcaustin/<NOSRV> -1/-1/-1/-1/10005 408 212 - - cR-- 44/44/24/0/0 0/0 "<BADREQ>" Jun 30 11:09:00 localhost haproxy[6320]: 68.197.56.2:52781 [30/Jun/2011:11:08:50.975] dcaustin dcaustin/<NOSRV> -1/-1/-1/-1/10000 408 212 - - cR-- 49/49/28/0/0 0/0 "<BADREQ>" From what I read on google, if i wanted to see what the bad requests are, I can show errors to the socket and it will spit them out. We do run a pretty heavily trafficed website and the percentage of "BADREQS" to normal requests is quite low, but I'd like to be able to get ahold of what that request WAS so I can debug it. stats # pxname,svname,qcur,qmax,scur,smax,slim,stot,bin,bout,dreq,dresp,ereq,econ,eresp,wretr,wredis,status,weight,act,bck,chkfail,chkdown,lastchg,downtime,qlimit,pid,iid,sid,throttle,lbtot,tracked,type,rate,rate_lim,rate_max, dcaustin,FRONTEND,,,64,120,50000,88433,105889100,2553809875,0,0,4641,,,,,OPEN,,,,,,,,,1,1,0,,,,0,45,0,128, dcaustin,web1,0,0,10,28,300,20941,25402112,633143416,,0,,0,3,0,0,UP,1,1,0,0,0,2208,0,,1,1,1,,20941,,2,11,,30, dcaustin,web2,0,0,9,30,300,20941,25026691,641475169,,0,,0,3,0,0,UP,1,1,0,0,0,2208,0,,1,1,2,,20941,,2,11,,30, dcaustin,web3,0,0,10,27,300,20940,30116527,635015040,,0,,0,9,0,0,UP,1,1,0,0,0,2208,0,,1,1,3,,20940,,2,10,,31, dcaustin,web4,0,0,5,28,300,20940,25343770,643209546,,0,,0,8,0,0,UP,1,1,0,0,0,2208,0,,1,1,4,,20940,,2,11,,31, dcaustin,BACKEND,0,0,34,95,50000,83762,105889100,2553809875,0,0,,0,34,0,0,UP,4,4,0,,0,2208,0,,1,1,0,,83762,,1,43,,122, 88500 "Sessions" and 4500 errors. in the last 20 minutes.

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• Why did I fail to build ctags for vim?

  - by hugemeow

  I got the latest, unreleased version of the ctags source code from the svn repository using svn co https://ctags.svn.sourceforge.net/svnroot/ctags I ran ./configure, which failed with the following error: config.status: creating Makefile config.status: WARNING: 'Makefile.in' seems to ignore the --datarootdir setting config.status: error: cannot find input file: config.h.in [mirror@home ctags-5.7]$ echo $? 1 Then I created an empty file named config.h.in, and now ./configure succeed. configure: creating ./config.status config.status: creating Makefile config.status: WARNING: 'Makefile.in' seems to ignore the --datarootdir setting config.status: creating config.h [mirror@home ctags-5.7]$ echo $? 0 Running make still failed. [mirror@home ctags-5.7]$ make gcc -I. -I. -DHAVE_CONFIG_H -g -O2 -c args.c In file included from args.c:17: /usr/include/stdio.h:88: error: two or more data types in declaration specifiers make: *** [args.o] Error 1 Why did this not work? How do I build ctags from the svn repository?

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• Creating a secure multicast tunnel with socat

  - by ams

  How we can create secure multicast tunnels ith socat? Assume that we have a list of IP address, CIDR network addresses that we want to create secure tunnel to them. I found this: socat STDIO UDP4-DATAGRAM:224.1.0.1:6666,range=192.168.10.0/24 but I want a secure tunnel and different adds with net addrs I want to create script that give the IPs and net addresses and creates a secure tunnel ./myscript IP1 NetAdd1 IP2 NetAdd2 .... How can I send these parameters to socat? Does socat multicast have any limits?

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• creating secure multicast with socat

  - by arash

  How we can create secure tunnels multicast with socat? Assume we have a list of ip address, CIDR network addresses that we want to create secure tunnel to them. I found this socat STDIO UDP4-DATAGRAM:224.1.0.1:6666,range=192.168.10.0/24 but I want a secure tunnel and different adds with net addrs I want to create script that give the IPs and net addresses and create secure tunnel ./myscript IP1 NetAdd1 IP2 NetAdd2 .... how can i send this parametersw to socat? Socat multicast hasn't any limits? Thanks for your help

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• How can I fix my C++ compiler as it isn't loaded by default?

  - by GNR

  Recently I had installed the Ubuntu flavour of the Linux operating system. I had opened a terminal and just wrote a sample C program to check if it is compiling. When I saved the sample file and compiled with cc a.c, errors comes that the standard library is not loaded (i.e stdio.h). When I went to help pages, it says that the C or C++ compiler doesnt gets loaded by default and we should do it ourselves. So can anyone help me out to fix this problem, i.e to load the C/C++ compiler.

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• Man pages in Linux

  - by Ayos

  I don't seem to have all the man pages that I need. For example, my college computers (running Fedora 14) have man pages for ASCII, all the standard C libraries (stdlib.h, stdio.h) and so on and so forth. I wish to "install" these pages, after looking up on the Internet I couldn't really find anything that made sense. How can I get, say, the man-page of ASCII (I know it's not really a command or a daemon or anything like that, but typing man ASCII on the college computer gets me a page with the ASCII value table + a little more information). I don't want to keep using the Internet for looking up man pages every time I need to look up a function, function prototype or the ASCII table or something like that.

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• Padding error - when using AES Encryption in Java and Decryption in C

  - by user234445

  Hi All, I have a problem while decrypting the xl file in rijndael 'c' code (The file got encrypted in Java through JCE) and this problem is happening only for the excel files types which having formula's. Remaining all file type encryption/decryption is happening properly. (If i decrypt the same file in java the output is coming fine.) While i am dumped a file i can see the difference between java decryption and 'C' file decryption. od -c -b filename(file decrypted in C) 0034620 005 006 \0 \0 \0 \0 022 \0 022 \0 320 004 \0 \0 276 4 005 006 000 000 000 000 022 000 022 000 320 004 000 000 276 064 0034640 \0 \0 \0 \0 \f \f \f \f \f \f \f \f \f \f \f \f 000 000 000 000 014 014 014 014 014 014 014 014 014 014 014 014 0034660 od -c -b filename(file decrypted in Java) 0034620 005 006 \0 \0 \0 \0 022 \0 022 \0 320 004 \0 \0 276 4 005 006 000 000 000 000 022 000 022 000 320 004 000 000 276 064 0034640 \0 \0 \0 \0 000 000 000 000 0034644 (the above is the difference between the dumped files) The following java code i used to encrypt the file. public class AES { /** * Turns array of bytes into string * * @param buf Array of bytes to convert to hex string * @return Generated hex string */ public static void main(String[] args) throws Exception { File file = new File("testxls.xls"); byte[] lContents = new byte[(int) file.length()]; try { FileInputStream fileInputStream = new FileInputStream(file); fileInputStream.read(lContents); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e1) { e1.printStackTrace(); } try { KeyGenerator kgen = KeyGenerator.getInstance("AES"); kgen.init(256); // 192 and 256 bits may not be available // Generate the secret key specs. SecretKey skey = kgen.generateKey(); //byte[] raw = skey.getEncoded(); byte[] raw = "aabbccddeeffgghhaabbccddeeffgghh".getBytes(); SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES"); Cipher cipher = Cipher.getInstance("AES"); cipher.init(Cipher.ENCRYPT_MODE, skeySpec); byte[] encrypted = cipher.doFinal(lContents); cipher.init(Cipher.DECRYPT_MODE, skeySpec); byte[] original = cipher.doFinal(lContents); FileOutputStream f1 = new FileOutputStream("testxls_java.xls"); f1.write(original); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } } I used the following file for decryption in 'C'. #include <stdio.h> #include "rijndael.h" #define KEYBITS 256 #include <stdio.h> #include "rijndael.h" #define KEYBITS 256 int main(int argc, char **argv) { unsigned long rk[RKLENGTH(KEYBITS)]; unsigned char key[KEYLENGTH(KEYBITS)]; int i; int nrounds; char dummy[100] = "aabbccddeeffgghhaabbccddeeffgghh"; char *password; FILE *input,*output; password = dummy; for (i = 0; i < sizeof(key); i++) key[i] = *password != 0 ? *password++ : 0; input = fopen("doc_for_logu.xlsb", "rb"); if (input == NULL) { fputs("File read error", stderr); return 1; } output = fopen("ori_c_res.xlsb","w"); nrounds = rijndaelSetupDecrypt(rk, key, 256); while (1) { unsigned char plaintext[16]; unsigned char ciphertext[16]; int j; if (fread(ciphertext, sizeof(ciphertext), 1, input) != 1) break; rijndaelDecrypt(rk, nrounds, ciphertext, plaintext); fwrite(plaintext, sizeof(plaintext), 1, output); } fclose(input); fclose(output); }

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• c - dereferencing issue

  - by Joe

  Hi, I have simplified an issue that I've been having trying to isolate the problem, but it is not helping. I have a 2 dimensional char array to represent memory. I want to pass a reference to that simulation of memory to a function. In the function to test the contents of the memory I just want to iterate through the memory and print out the contents on each row. The program prints out the first row and then I get seg fault. My program is as follows: #include <stdio.h> #include <stdlib.h> #include <ctype.h> #include <string.h> void test_memory(char*** memory_ref) { int i; for(i = 0; i < 3; i++) { printf("%s\n", *memory_ref[i]); } } int main() { char** memory; int i; memory = calloc(sizeof(char*), 20); for(i = 0; i < 20; i++) { memory[i] = calloc(sizeof(char), 33); } memory[0] = "Mem 0"; memory[1] = "Mem 1"; memory[2] = "Mem 2"; printf("memory[1] = %s\n", memory[1]); test_memory(&memory); return 0; } This gives me the output: memory[1] = Mem 1 Mem 0 Segmentation fault If I change the program and create a local version of the memory in the function by dereferencing the memory_ref, then I get the right output: So: #include <stdio.h> #include <stdlib.h> #include <ctype.h> #include <string.h> void test_memory(char*** memory_ref) { char** memory = *memory_ref; int i; for(i = 0; i < 3; i++) { printf("%s\n", memory[i]); } } int main() { char** memory; int i; memory = calloc(sizeof(char*), 20); for(i = 0; i < 20; i++) { memory[i] = calloc(sizeof(char), 33); } memory[0] = "Mem 0"; memory[1] = "Mem 1"; memory[2] = "Mem 2"; printf("memory[1] = %s\n", memory[1]); test_memory(&memory); return 0; } gives me the following output: memory[1] = Mem 1 Mem 0 Mem 1 Mem 2 which is what I want, but making a local version of the memory is useless because I need to be able to change the values of the original memory from the function which I can only do by dereferencing the pointer to the original 2d char array. I don't understand why I should get a seg fault on the second time round, and I'd be grateful for any advice. Many thanks Joe

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• seg fault caused by malloc and sscanf in a function

  - by Framester

  Hi, I want to open a text file (see below), read the first int in every line and store it in an array, but I get an segmentation fault. I got rid of all gcc warnings, I read through several tutorials I found on the net and searched stackoverflow for solutions, but I could't make out, what I am doing wrong. It works when I have everything in the main function (see example 1), but not when I transfer it to second function (see example 2 further down). In example 2 I get, when I interpret gdb correctly a seg fault at sscanf (line,"%i",classes[i]);. I'm afraid, it could be something trivial, but I already wasted one day on it. Thanks in advance. [Example 1] Even though that works with everything in main: #include<stdio.h> #include<stdlib.h> #include<string.h> const int LENGTH = 1024; int main() { char *filename="somedatafile.txt"; int *classes; int lines; FILE *pfile = NULL; char line[LENGTH]; pfile=fopen(filename,"r"); int numlines=0; char *p; while(fgets(line,LENGTH,pfile)){ numlines++; } rewind(pfile); classes=(int *)malloc(numlines*sizeof(int)); if(classes == NULL){ printf("\nMemory error."); exit(1); } int i=0; while(fgets(line,LENGTH,pfile)){ printf("\n"); p = strtok (line," "); p = strtok (NULL, ", "); sscanf (line,"%i",&classes[i]); i++; } fclose(pfile); return 1; } [Example 2] This does not with the functionality transfered to a function: #include<stdio.h> #include<stdlib.h> #include<string.h> const int LENGTH = 1024; void read_data(int **classes,int *lines, char *filename){ FILE *pfile = NULL; char line[LENGTH]; pfile=fopen(filename,"r"); int numlines=0; char *p; while(fgets(line,LENGTH,pfile)){ numlines++; } rewind(pfile); * classes=(int *)malloc(numlines*sizeof(int)); if(*classes == NULL){ printf("\nMemory error."); exit(1); } int i=0; while(fgets(line,LENGTH,pfile)){ printf("\n"); p = strtok (line," "); p = strtok (NULL, ", "); sscanf (line,"%i",classes[i]); i++; } fclose(pfile); *lines=numlines; } int main() { char *filename="somedatafile.txt"; int *classes; int lines; read_data(&classes, &lines,filename) ; for(int i=0;i<lines;i++){ printf("\nclasses[i]=%i",classes[i]); } return 1; } [Content of somedatafile.txt] 50 21 77 0 28 0 27 48 22 2 55 0 92 0 0 26 36 92 56 4 53 0 82 0 52 -5 29 30 2 1 37 0 76 0 28 18 40 48 8 1 37 0 79 0 34 -26 43 46 2 1 85 0 88 -4 6 1 3 83 80 5 56 0 81 0 -4 11 25 86 62 4 55 -1 95 -3 54 -4 40 41 2 1 53 8 77 0 28 0 23 48 24 4 37 0 101 -7 28 0 64 73 8 1 ...

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• Problem in transfering file from server to client using C sockets

  - by coolrockers2007

  I want to ask, why I cannot transfer file from server to client? When I start to send the file from server, the client side program will have problem. So, I spend some times to check the code, But I still cannot find out the problem Can anyone point out the problem for me? CLIENTFILE.C #include stdio.h #include stdlib.h #include time.h #include netinet/in.h #include fcntl.h #include sys/types.h #include string.h #include stdarg.h #define PORT 5678 #define MLEN 1000 int main(int argc, char *argv []) { int sockfd; int number,message; char outbuff[MLEN],inbuff[MLEN]; //char PWD_buffer[_MAX_PATH]; struct sockaddr_in servaddr; FILE *fp; int numbytes; char buf[2048]; if (argc != 2) fprintf(stderr, "error"); if ( (sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) fprintf(stderr, "socket error"); memset(&servaddr, 0, sizeof(servaddr)); servaddr.sin_family = AF_INET; servaddr.sin_port = htons(PORT); if (connect(sockfd, (struct sockaddr *) &servaddr, sizeof(servaddr)) < 0) fprintf(stderr, "connect error"); if ( (fp = fopen("/home/na/nall9047/write.txt", "w")) == NULL){ perror("fopen"); exit(1); } printf("Still NO PROBLEM!\n"); //Receive file from server while(1){ numbytes = read(sockfd, buf, sizeof(buf)); printf("read %d bytes, ", numbytes); if(numbytes == 0){ printf("\n"); break; } numbytes = fwrite(buf, sizeof(char), numbytes, fp); printf("fwrite %d bytes\n", numbytes); } fclose(fp); close(sockfd); return 0; } SERVERFILE.C #include stdio.h #include fcntl.h #include stdlib.h #include time.h #include string.h #include netinet/in.h #include errno.h #include sys/types.h #include sys/socket.h #includ estdarg.h #define PORT 5678 #define MLEN 1000 int main(int argc, char *argv []) { int listenfd, connfd; int number, message, numbytes; int h, i, j, alen; int nread; struct sockaddr_in servaddr; struct sockaddr_in cliaddr; FILE *in_file, *out_file, *fp; char buf[4096]; listenfd = socket(AF_INET, SOCK_STREAM, 0); if (listenfd < 0) fprintf(stderr,"listen error") ; memset(&servaddr, 0, sizeof(servaddr)); servaddr.sin_family = AF_INET; servaddr.sin_addr.s_addr = htonl(INADDR_ANY); servaddr.sin_port = htons(PORT); if (bind(listenfd, (struct sockaddr *) &servaddr, sizeof(servaddr)) < 0) fprintf(stderr,"bind error") ; alen = sizeof(struct sockaddr); connfd = accept(listenfd, (struct sockaddr *) &cliaddr, &alen); if (connfd < 0) fprintf(stderr,"error connecting") ; printf("accept one client from %s!\n", inet_ntoa(cliaddr.sin_addr)); fp = fopen ("/home/na/nall9047/read.txt", "r"); // open file stored in server if (fp == NULL) { printf("\nfile NOT exist"); } //Sending file while(!feof(fp)){ numbytes = fread(buf, sizeof(char), sizeof(buf), fp); printf("fread %d bytes, ", numbytes); numbytes = write(connfd, buf, numbytes); printf("Sending %d bytes\n",numbytes); } fclose (fp); close(listenfd); close(connfd); return 0; }

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• [C++] Adding a string or char array to a byte vector

  - by xeross

  I'm currently working on a class to create and read out packets send through the network, so far I have it working with 16bit and 8bit integers (Well unsigned but still). Now the problem is I've tried numerous ways of copying it over but somehow the _buffer got mangled, it segfaulted, or the result was wrong. I'd appreciate if someone could show me a working example. My current code can be seen below. Thanks, Xeross Main #include <iostream> #include <stdio.h> #include "Packet.h" using namespace std; int main(int argc, char** argv) { cout << "#################################" << endl; cout << "# Internal Use Only #" << endl; cout << "# Codename PACKETSTORM #" << endl; cout << "#################################" << endl; cout << endl; Packet packet = Packet(); packet.SetOpcode(0x1f4d); cout << "Current opcode is: " << packet.GetOpcode() << endl << endl; packet.add(uint8_t(5)) .add(uint16_t(4000)) .add(uint8_t(5)); for(uint8_t i=0; i<10;i++) printf("Byte %u = %x\n", i, packet._buffer[i]); printf("\nReading them out: \n1 = %u\n2 = %u\n3 = %u\n4 = %s", packet.readUint8(), packet.readUint16(), packet.readUint8()); return 0; } Packet.h #ifndef _PACKET_H_ #define _PACKET_H_ #include <iostream> #include <vector> #include <stdio.h> #include <stdint.h> #include <string.h> using namespace std; class Packet { public: Packet() : m_opcode(0), _buffer(0), _wpos(0), _rpos(0) {} Packet(uint16_t opcode) : m_opcode(opcode), _buffer(0), _wpos(0), _rpos(0) {} uint16_t GetOpcode() { return m_opcode; } void SetOpcode(uint16_t opcode) { m_opcode = opcode; } Packet& add(uint8_t value) { if(_buffer.size() < _wpos + 1) _buffer.resize(_wpos + 1); memcpy(&_buffer[_wpos], &value, 1); _wpos += 1; return *this; } Packet& add(uint16_t value) { if(_buffer.size() < _wpos + 2) _buffer.resize(_wpos + 2); memcpy(&_buffer[_wpos], &value, 2); _wpos += 2; return *this; } uint8_t readUint8() { uint8_t result = _buffer[_rpos]; _rpos += sizeof(uint8_t); return result; } uint16_t readUint16() { uint16_t result; memcpy(&result, &_buffer[_rpos], sizeof(uint16_t)); _rpos += sizeof(uint16_t); return result; } uint16_t m_opcode; std::vector<uint8_t> _buffer; protected: size_t _wpos; // Write position size_t _rpos; // Read position }; #endif // _PACKET_H_

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• Want to Receive dynamic length data from a message queue in IPC?

  - by user1089679

  Here I have to send and receive dynamic data using a SysV message queue. so in structure filed i have dynamic memory allocation char * because its size may be varies. so how can i receive this type of message at receiver side. Please let me know how can i send dynamic length of data with message queue. I am getting problem in this i posted my code below. send.c /*filename : send.c *To compile : gcc send.c -o send */ #include <stdio.h> #include <stdlib.h> #include <errno.h> #include <string.h> #include <sys/types.h> #include <sys/ipc.h> #include <sys/msg.h> struct my_msgbuf { long mtype; char *mtext; }; int main(void) { struct my_msgbuf buf; int msqid; key_t key; static int count = 0; char temp[5]; int run = 1; if ((key = ftok("send.c", 'B')) == -1) { perror("ftok"); exit(1); } printf("send.c Key is = %d\n",key); if ((msqid = msgget(key, 0644 | IPC_CREAT)) == -1) { perror("msgget"); exit(1); } printf("Enter lines of text, ^D to quit:\n"); buf.mtype = 1; /* we don't really care in this case */ int ret = -1; while(run) { count++; buf.mtext = malloc(50); strcpy(buf.mtext,"Hi hello test message here"); snprintf(temp, sizeof (temp), "%d",count); strcat(buf.mtext,temp); int len = strlen(buf.mtext); /* ditch newline at end, if it exists */ if (buf.mtext[len-1] == '\n') buf.mtext[len-1] = '\0'; if (msgsnd(msqid, &buf, len+1, IPC_NOWAIT) == -1) /* +1 for '\0' */ perror("msgsnd"); if(count == 100) run = 0; usleep(1000000); } if (msgctl(msqid, IPC_RMID, NULL) == -1) { perror("msgctl"); exit(1); } return 0; } receive.c /* filename : receive.c * To compile : gcc receive.c -o receive */ #include <stdio.h> #include <stdlib.h> #include <errno.h> #include <sys/types.h> #include <sys/ipc.h> #include <sys/msg.h> struct my_msgbuf { long mtype; char *mtext; }; int main(void) { struct my_msgbuf buf; int msqid; key_t key; if ((key = ftok("send.c", 'B')) == -1) { /* same key as send.c */ perror("ftok"); exit(1); } if ((msqid = msgget(key, 0644)) == -1) { /* connect to the queue */ perror("msgget"); exit(1); } printf("test: ready to receive messages, captain.\n"); for(;;) { /* receive never quits! */ buf.mtext = malloc(50); if (msgrcv(msqid, &buf, 50, 0, 0) == -1) { perror("msgrcv"); exit(1); } printf("test: \"%s\"\n", buf.mtext); } return 0; }

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• Two functions working but not when I put them together

  - by Error_404

  I'm really new to C(I have been learning Cuda and wanted to learn C so I can run everything together instead of generating data in Java/Python and copy/pasting it manually to my Cuda program to play with). I am trying to open a large file(20+gb) and parse some data but because I was having problems I decided to try to break down my problem first to verify I can open and read line by line a file and then in another file take a sample of the output of a line and try to parse it, then if all goes well I can simply bring them together. I managed(after a bit of a struggle) to get each part working but when I combine them together it doesn't work(I tried in both eclipse & QT creator. QT creator says it exited unexpectedly and eclipse just stops..). Here's the parsing part(it works exactly as I want): #include <string.h> #include <stdio.h> int main() { char line[1024] = "[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 2, 2, 4],"; size_t len = strlen(line); memmove(line, line+1, len-3); line[len-3] = 0; printf("%s \n",line); char str[100], *s = str, *t = NULL; strcpy(str, line); while ((t = strtok(s, " ,")) != NULL) { s = NULL; printf(":%s:\n", t); } return 0; } The data in variable line is exactly as I get if I print each line of a file. But when I copy/paste it into my main program then it doesn't work(QT shows nothing and eclipse just shows the first line). This code is just a few file IO commands that are wrapped around the commands above(everything within the while loop is the exact same as above) #include <stdio.h> #include <stdlib.h> int main() { char line[1024]; FILE *fp = fopen("/Users/me/Desktop/output.txt","r"); printf("Starting.. \n"); int count = 0; int list[30]; //items will be stored here while(fgets(line, 1024, fp) != NULL){ count++; //char line[1024] = "[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 2, 2, 4],"; size_t len = strlen(line); memmove(line, line+1, len-3); line[len-3] = 0; printf("%s \n",line); char str[100], *s = str, *t = NULL; strcpy(str, line); while ((t = strtok(s, " ,")) != NULL) { s = NULL; printf(":%s:\n", t); } } printf(" num of lines is %i \n", count); return 0; } eclipse output: Starting.. 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 2, 2, 4 I can't figure out what I'm doing wrong. I'm using a mac with gcc 4.2, if that helps. The only thing I can think of is maybe I'm doing something wrong the way I parse the list variable so its not accessible later on(I'm not sure its a wild guess). Is there anything I'm missing?

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• Alphabetically Ordering an array of words

  - by Genesis

  I'm studying C on my own in preparation for my upcoming semester of school and was wondering what I was doing wrong with my code so far. If Things look weird it is because this is part of a much bigger grab bag of sorting functions I'm creating to get a sense of how to sort numbers,letters,arrays,and the like! I'm basically having some troubles with the manipulation of strings in C currently. Also, I'm quite limited in my knowledge of C at the moment! My main Consists of this: #include <stdio.h> #include <stdio.h> #include <stdlib.h> int numbers[10]; int size; int main(void){ setvbuf(stdout,NULL,_IONBF,0); //This is magical code that allows me to input. int wordNumber; int lengthOfWord = 50; printf("How many words do you want to enter: "); scanf("%i", &wordNumber); printf("%i\n",wordNumber); char words[wordNumber][lengthOfWord]; printf("Enter %i words:",wordNumber); int i; for(i=0;i<wordNumber+1;i++){ //+1 is because my words[0] is blank. fgets(&words[i], 50, stdin); } for(i=1;i<wordNumber+1;i++){ // Same as the above comment! printf("%s", words[i]); //prints my words out! } alphabetize(words,wordNumber); //I want to sort these arrays with this function. } My sorting "method" I am trying to construct is below! This function is seriously flawed, but I'd thought I'd keep it all to show you where my mind was headed when writing this. void alphabetize(char a[][],int size){ // This wont fly. size = size+1; int wordNumber; int lengthOfWord; char sortedWords[wordNumber][lengthOfWord]; //In effort for the for loop int i; int j; for(i=1;i<size;i++){ //My effort to copy over this array for manipulation for(j=1;j<size;j++){ sortedWords[i][j] = a[i][j]; } } //This should be kinda what I want when ordering words alphabetically, right? for(i=1;i<size;i++){ for(j=2;j<size;j++){ if(strcmp(sortedWords[i],sortedWords[j]) > 0){ char* temp = sortedWords[i]; sortedWords[i] = sortedWords[j]; sortedWords[j] = temp; } } } for(i=1;i<size;i++){ printf("%s, ",sortedWords[i]); } } I guess I also have another question as well... When I use fgets() it's doing this thing where I get a null word for the first spot of the array. I have had other issues recently trying to scanf() char[] in certain ways specifically spacing my input word variables which "magically" gets rid of the first null space before the character. An example of this is using scanf() to write "Hello" and getting " Hello" or " ""Hello"... Appreciate any thoughts on this, I've got all summer to study up so this doesn't need to be answered with haste! Also, thank you stack overflow as a whole for being so helpful in the past. This may be my first post, but I have been a frequent visitor for the past couple of years and it's been one of the best places for helpful advice/tips.

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• C string question

  - by user208454

  I am writing a simple c program which reverses a string, taking the string from argv[1]. Here is the code: #include <stdio.h> #include <stdlib.h> #include <string.h> char* flip_string(char *string){ int i = strlen(string); int j = 0; // Doesn't really matter all I wanted was the same size string for temp. char* temp = string; puts("This is the original string"); puts(string); puts("This is the \"temp\" string"); puts(temp); for(i; i>=0; i--){ temp[j] = string[i] if (j <= strlen(string)) { j++; } } return(temp); } int main(int argc, char *argv[]){ puts(flip_string(argv[1])); printf("This is the end of the program\n"); } That's basically it, the program compiles and everything but does not return the temp string in the end (just blank space). In the beginning it prints temp fine when its equal to string. Furthermore if I do a character by character printf of temp in the for loop the correct temp string in printed i.e. string - reversed. just when I try to print it to standard out (after the for loop/ or in the main) nothing happens only blank space is printed.

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• C printf not working on ubuntu 13.10 terminal

  - by Blaze Tama

  First, im new in ubuntu so please bear with me. I need to create a C based program for a course in my university. I was using opensuse and its konsole when i was in the university's lab. So basically i need to install opensuse on my system or using a vmware. But i feel lazy to do that, so i tried to run it on my ubuntu instead of opensuse. However, no C code seems working on ubuntu's terminal. The compiling is success, but its not running, or at least the printf is not running. This is my code, a very very simple one : #include<stdio.h> #include<unistd.h> #include<stdlib.h> int main() { printf("test"); return 0; } When i compile it with gcc test.c -o test everything work fine and i get an executeable file. Then i try to run it by ./test, but the printf is not printed. No error or warning was shown. Am i missing something? Note : my gcc is the new one, it should has no problem. Thanks for your help :D

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• C Programming matrix

  - by Bilal Khan

  In this program the user enters the # of columns of the matrix and then the entries of the matrix. So, for example, if the user enters 2 for column # and 1 2 3 4 for entries then the program develops a 2 by 2 matrix with 1 2 3 4 as entries. My program works perfectly in such a case. However, if the user for example had only entered 1 2 3 then my program makes a matrix with garbage values. I would like the program in such a case to exit the program. It is a simple question, but it has me baffled. #include<stdio.h> #include<stdlib.h> int main() { int m,x, n, c = 0, d,k, matrix[10][10], transpose[10][10], product[10][10]; printf("Enter the number of columns of matrix "); scanf("%d",&m); if(m<=0){ printf("You entered a invalid value."); exit(0); } else{ printf("Enter the elements of matrix \n"); for( c = 0 ; c < 10 ; c++ ) { for( d = 0 ; d < m ; d++ ) { scanf("%d",&matrix[c][d]); if (matrix[c][d] == 99) // 'x' is character variable I declared to use as a break break; // c = c+1; } if (matrix[c][d] == 99) break; } } printf("\nHere is your matrix:\n"); int i; for(i=0;i<c;i++) { for(d=0;d<m;d++) { printf("%3d ",matrix[i][d]); } printf("\n"); }

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• Problem using graphics.h in Ubuntu

  - by blooooomer

  # include<stdio.h> # include<graphics.h> # include<math.h> using namespace std; int main(void) { int gd=DETECT,gm; int r,x,y,p,xc=320,yc=240; initgraph(&gd,&gm,NULL); cleardevice(); printf("Enter the radius "); scanf("%d",&r); x=0; y=r; putpixel(xc+x,yc-y,1); p=3-(2*r); for(x=0;x<=y;x++) { if (p<0) { y=y; p=(p+(4*x)+6); } else { y=y-1; p=p+((4*(x-y)+10)); } putpixel(xc+x,yc-y,1); putpixel(xc-x,yc-y,2); putpixel(xc+x,yc+y,3); putpixel(xc-x,yc+y,4); putpixel(xc+y,yc-x,5); putpixel(xc-y,yc-x,6); putpixel(xc+y,yc+x,7); putpixel(xc-y,yc+x,8); } getch(); closegraph(); } installed graphics.h compiled using gcc filename.cpp -0 filename -lgraph then used ./filename the window apperared for 10 seconds and the error below appears: [xcb] Unknown sequence number while processing queue [xcb] Most likely this is a multi-threaded client and XInitThreads has not been called [xcb] Aborting, sorry about that. heart: ../../src/xcb_io.c:273: poll_for_event: Assertion `!xcb_xlib_threads_sequence_lost' failed. Aborted Any solutions?

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• GSL Uniform Random Number Generator

  - by Jamaia

  I want to use GSL's uniform random number generator. On their website, they include this sample code: #include <stdio.h> #include <gsl/gsl_rng.h> int main (void) { const gsl_rng_type * T; gsl_rng * r; int i, n = 10; gsl_rng_env_setup(); T = gsl_rng_default; r = gsl_rng_alloc (T); for (i = 0; i < n; i++) { double u = gsl_rng_uniform (r); printf ("%.5f\n", u); } gsl_rng_free (r); return 0; } However, this does not rely on any seed and so, the same random numbers will be produced each time. They also specify the following: The generator itself can be changed using the environment variable GSL_RNG_TYPE. Here is the output of the program using a seed value of 123 and the multiple-recursive generator mrg, $ GSL_RNG_SEED=123 GSL_RNG_TYPE=mrg ./a.out But I don't understand how to implement this. Any ideas as to what modifications I can make to the above code to incorporate the seed?

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• Parsing mathematical experssions with two values that have parenthesis and minus signs

  - by user45921

  I'm trying to parse equations like these which only has two values or the square root of a certain value from a text file: 100+100 -100-100 -(100)+(-100) sqrt(100) by the minues signs, parenthesis and the operator symbol in the middle and the square root, and I have no idea how to start off... I've got the file part done and the simple calculation parts except that I couldnt get my program to solve the equations in the above. #include <stdio.h> #include <string.h> #include <stdlib.h> #include <math.h> main(){ FILE *fp; char buff[255], sym,sym2,del1,del2,del3,del4; double num1, num2; int ret; fp = fopen("input.txt","r"); while(fgets(buff,sizeof(buff),fp)!=NULL){ char *tok = buff; sscanf(tok,"%lf%c%lf",&num1,&sym,&num2); switch(sym){ case '+': printf("%lf\n", num1+num2); break; case '-': printf("%lf\n", num1-num2); break; case '*': printf("%lf\n", num1*num2); break; case '/': printf("%lf\n", num1/num2); break; default: printf("The input value is not correct\n"); break; } } fclose(fp); } that is what have I written for the other basic operations without parenthesis and the minus sign for the second value and it works great for the simple ones. I'm using a switch method to calculate the add, sub, mul and divide but I'm not sure how to properly use the sscanf function (if I am not using it properly) or if there is another way using a function like strtok to properly parse the parenthesis and the minus signs. Any kind help?

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• Problem with alleg42.dll / program crashes / Allegro & Codeblocks

  - by user24152

  I'm having a serious problem with allegro. The program should display random pixels on the screen and when I build and run it I get the following error message: Below is the full code of my program: #include <stdio.h> #include <stdlib.h> #include <time.h> #include "allegro.h" #define Text_Color_Red makecol(255,0,0) int main() { int ret; int color_depth = 32; int x; int y; int red; int green; int blue; int color; //init allegro allegro_init(); //install keyboard install_keyboard(); //set color depth to 32 bits set_color_depth(color_depth); //init random seed srand(time(NULL)); //init video mode to 640 x 480 ret = set_gfx_mode(GFX_AUTODETECT_WINDOWED,640,480,0,0); if(ret !=0) { allegro_message(allegro_error); return 1; } //Display string textprintf(screen,font,0,0,10,0,Text_Color_Red,"Screen Resolution is: %dx%d -- Press ESC to quit !",SCREEN_W,SCREEN_H); //display pixels until ESC key is pressed //wait for keypress while(!key[KEY_ESC]) { //set a random location x = 10 + rand() % (SCREEN_W-20); y = 10 + rand() % (SCREEN_H-20); //set a random color red = rand() % 255; green = rand() % 255; blue = rand() % 255; color = makecol(red,green,blue); //draw the pixel putpixel(screen, x, y, color); } //quit allegro allegro_exit(); } END_OF_MAIN() Error message: AllegroPixels1.exe has encountered a problem and needs to close. We are sorry for the inconvenience. Error signature: AppName: allegropixels1.exe AppVer: 0.0.0.0 ModName: alleg42.dll ModVer: 4.2.3.0 Offset: 0006c05c I am using Windows XP inside a virtual machine under Parallels 7.0

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