March 2006 - openSUSE Programming - openSUSE Mailing Lists

The meaning of atomic in write()
by Verdi March 08 Apr '06

08 Apr '06

Hi, The open group specification says that write() is atomic as long as the number of bytes is not larger than PIPE_BUF. In the following program, sometimes only one process successfully writes to the file. I thought that fprintf also uses write() underneath, so the file should contains strings from both processes. Any insight? #include <stdio.h> #include <limits.h> #include <assert.h> int main() { int i; FILE *f; printf("bufsiz=%d pipe_buf=%d\n", BUFSIZ, PIPE_BUF); f = fopen( "test.txt" , "w" ); /* f = stdout; */ fprintf( f, "Parent is process %d\n", getpid() ); assert(fork() >= 0); for (i=1; i<4; i++) fprintf( f, " %8d: %d\n", getpid(), i ); fclose( f ); return 0; } Here are some results, the first correctly contains strings from both processes, but the second only contains strings from one process: cincai@verdimar:/tmp> ./a.out; cat haha.txt bufsiz=8192 pipe_buf=4096 Parent is process 25831 25832: 1 25832: 2 25832: 3 bufsiz=8192 pipe_buf=4096 Parent is process 25831 25831: 1 25831: 2 25831: 3 cincai@verdimar:/tmp> ./a.out ;cat haha.txt bufsiz=8192 pipe_buf=4096 Parent is process 25836 25837: 1 25837: 2 25837: 3 -- Bis zu 70% Ihrer Onlinekosten sparen: GMX SmartSurfer! Kostenlos downloaden: http://www.gmx.net/de/go/smartsurfer

6 22

FileUpload.1.1 and http status 500
by Patrix Linux 30 Mar '06

30 Mar '06

Dear friends, I am writing a program for uploading a file onto my webserver with JSP. I use JSP, Tomcat, Apache2, MySQL. I use this program : http://jakarta.apache.org/commons/fileupload/ . I choose the version 1.1. But it does not run properly as I expect (HTTP Status 500). Please tell me where the mistake. Thank you very much in advance. ----- // This is my 'ps.jsp' : <body> <table cellpadding="0" cellspacing="0" border="1" align="center"> <form enctype="multipart/form-data" action="http://localhost:8080/penguin-teknologi/penguin-teaches/cgiupload.jsp" method="post" name="myform"> <tr><td align="justify"><font style="Comic Sans MS, Arial">Silahkan pilih file yg akan diupload.</font></td></tr> <tr><td><input type="text" name="nama"></td></tr> <tr><td align="justify"><input type="file" name="soalnya"></td></tr> <tr><td align="justify"><input type="submit" value="Kirim"><input type="reset"></td></tr> </form> </table> </body> ----- // This is my 'cgiupload.jsp' <%@ page import="org.apache.commons.fileupload.*, java.util.List, java.io.File, java.util.Iterator" %> <% boolean isMultipart = FileUpload.isMultipartContent(request); if(!isMultipart){ request.setAttribute("msg", "Request was not multipart!"); request.getRequestDispatcher("msg.jsp").forward(request, response); return; } DiskFileUpload upload = new DiskFileUpload(); List items = upload.parseRequest(request); Iterator itr = items.iterator(); while(itr.hasNext()){ FileItem item = (FileItem) itr.next(); if(item.isFormField()) { String fieldName = item.getFieldName(); if(fieldName.equals("name")) request.setAttribute("msg", "Thank You: " + item.getString()); } else { File fullFile = new File(item.getName()); File savedFile = new File(getServletContext().getRealPath("/"), fullFile.getName()); item.write(savedFile); } } request.getRequestDispatcher("msg.jsp").forward(request, response); %> ----- // This is my 'msg.jsp' : <body> <% String msg = (String)request.getAttribute("msg"); if(msg != null) out.println("<font size=+1>Buseettt<br>" + msg + "</font><br/>"); %> Click <a href="../../../../../Apache%20Group/Apache2/htdocs/p-tek/penguin-teaches/ps.jsp">here</a> to go to the upload page. </body> ----- HTTP Status 500 - -------------------------------------------------------------------------------- type Exception report message description The server encountered an internal error () that prevented it from fulfilling this request. exception org.apache.jasper.JasperException: org/apache/commons/io/output/DeferredFileOutputStream org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:510) org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:375) org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314) org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264) javax.servlet.http.HttpServlet.service(HttpServlet.java:802) root cause javax.servlet.ServletException: org/apache/commons/io/output/DeferredFileOutputStream org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:858) org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:791) org.apache.jsp.penguin_002dteaches.cgiupload_jsp._jspService(cgiupload_jsp.java:80) org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97) javax.servlet.http.HttpServlet.service(HttpServlet.java:802) org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:332) org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314) org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264) javax.servlet.http.HttpServlet.service(HttpServlet.java:802) root cause java.lang.NoClassDefFoundError: org/apache/commons/io/output/DeferredFileOutputStream org.apache.commons.fileupload.DefaultFileItemFactory.createItem(DefaultFileItemFactory.java:102) org.apache.commons.fileupload.FileUploadBase.createItem(FileUploadBase.java:500) org.apache.commons.fileupload.FileUploadBase.parseRequest(FileUploadBase.java:367) org.apache.commons.fileupload.FileUploadBase.parseRequest(FileUploadBase.java:268) org.apache.jsp.penguin_002dteaches.cgiupload_jsp._jspService(cgiupload_jsp.java:57) org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97) javax.servlet.http.HttpServlet.service(HttpServlet.java:802) org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:332) org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314) org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264) javax.servlet.http.HttpServlet.service(HttpServlet.java:802) note The full stack trace of the root cause is available in the Apache Tomcat/5.5.16 logs. -------------------------------------------------------------------------------- Apache Tomcat/5.5.16

2 4

Position independent code (?)
by Anders Johansson 29 Mar '06

29 Mar '06

Hi, I'm trying to compile a program on x86_64, but when it gets to the final linking stage, I get the error relocation R_X86_64_PC32 against `prefetch_C_withmask' can not be used when making a shared object; recompile with -fPIC I've tried putting -fPIC every place I can find where it is legal to do so, but I still always get the same error Does anyone know what this relocation is, and why I keep getting the error?

5 14

Sign-unsigned widening conversion in C
by Verdi March 29 Mar '06

29 Mar '06

Hi, is there a standard rule on widening conversion between signed and unsigned type? I found a reference from this URL: http://developers.sun.com/prodtech/cc/articles/ILP32toLP64Issues.html which also seems to be implemented by gcc. Can anybody confirm on this? TIA. int main() { unsigned int ui = 0xcabcdef2; long long ll_ui = ui; unsigned long long ull_ui = ui; int i = 0xcabcdef2; long long ll_i = i; unsigned long long ull_i = i; printf("ui=%x ll_ui=%llx ull_ui=%llx\n", ui, ll_ui, ull_ui); printf("i=%x ll_i=%llx ull_i=%llx%\n", i, ll_i, ull_i); return 0; } Execution result: ui=cabcdef2 ll_ui=cabcdef2 ull_ui=cabcdef2 i=cabcdef2 ll_i=ffffffffcabcdef2 ull_i=ffffffffcabcdef2 -- Regards, Verdi -- Echte DSL-Flatrate dauerhaft f�r 0,- Euro*! "Feel free" mit GMX DSL! http://www.gmx.net/de/go/dsl

2 3

Re: [suse-programming-e] The meaning of atomic in write()
by Verdi March 28 Mar '06

28 Mar '06

> --- Ursprüngliche Nachricht --- > Von: Ken Jennings <ken_jennings(a)bellsouth.net> > An: "Verdi March" <cincaipatron(a)gmx.net> > Betreff: Re: [suse-programming-e] The meaning of atomic in write() > Datum: Tue, 28 Mar 2006 01:00:49 -0500 > Are you sure haha.txt is the file? The code says it opens test.txt for > write. Sorry typo :), should be test.txt. And I rerun it to confirm the result is as what I've described. cincai@verdimar:/tmp> ./a.out; cat test.txt bufsiz=8192 pipe_buf=4096 Parent is process 29077 29077: 1 29077: 2 29077: 3 cincai@verdimar:/tmp> ./a.out; cat test.txt bufsiz=8192 pipe_buf=4096 Parent is process 29082 29083: 1 29083: 2 29083: 3 Parent is process 29082 29082: 1 29082: 2 29082: 3 -- Regards, Verdi -- "Feel free" mit GMX FreeMail! Monat für Monat 10 FreeSMS inklusive! http://www.gmx.net

1 0

What is the easiest way to downgrade g++?
by Darrell Cormier 24 Mar '06

24 Mar '06

I am running SuSE Linux 10.0 which ships with g++ 4.0.2. However, several of my programs that were working fine under 3.3.5 will not build under 4.0.2. I consistently get the following errors: /usr/include/c++/4.0.2/bits/sstream.tcc:112: error: expected unqualified-id before '(' token /usr/include/c++/4.0.2/bits/sstream.tcc:114: error: expected unqualified-id before '(' token I would like to downgrade my c++ environment to 3.3.x so I can get back to where I was (working!). What is the most direct/quickest way to get back where I was? I noticed that 3.3.x is not on the DVD. Thanks, Darrell

3 8

System call priority
by Pierre Patino 20 Mar '06

20 Mar '06

Greeting I've got a kernel module that contains something like this: while(loop) { take semaphore A do some I/O on the PCI bus give semaphore A } This loop is launched by a worker thread Meanwhile, I've got write() mapped into a module function like this: my_write() { take semaphore A write to the PCI pus give semaphore A } The problem is that my_write() can never get the A semaphore. The loop is too tight perhaps. Or maybe the system call has a lower priority than the kernel's worker thread. Other than using flags, is there some easy way to fix this? TIA&Cheers

3 3

Help with Tcl/Tk 2-D GUI
by Maura Edeweiss Monville 19 Mar '06

19 Mar '06

I'm starting a new job in a few days. One of my first tasks will be to modify th 2-D GUI of a package. In the following I'll have to evolve the 2-D GUI into a 3-D GUI allowing for 3-D rotations of 3-D structures. I've never used Tcl/Tk in my life so I would greatly appreciate some advice about an easy tutorial with plenty of worked out examples ... if available. I'm running SuSE 9.3 on my laptop and have zero time to replace it with SuSe 10 for the time being. Thank you in advance for your help. Maura

3 7

multi-threading and fork()ing?
by Per Jessen 09 Mar '06

09 Mar '06

Anything in particular I need to be aware of in an application that is multi-threaded, but also does regular forks? I've studied some of the stuff talked about in the man-page for pthread_atfork(), and none of it applies to my situation. I don't think I have a specific problem with fork(), I'm just trying to eliminate that option. /Per Jessen, Zürich

3 3

Xerces XMLCh UTF-16 Linux vs Reality
by Steven T. Hatton 09 Mar '06

09 Mar '06

On the Xerces C++ mailing list I was told the following: "XMLCh is specifically UTF-16. But wchar_t is not UTF-16 everywhere. It's non-portable, and Solaris and Linux each use different (including from each other) encodings for wchar_t. There's actually a gcc option to make wchar_t the same as on Windows, it was created for Wine. I'm not brave enough to rely on it." The Qt documentation tells me: <quote url=http://doc.trolltech.com/4.1/qstring.html> The QString class provides a Unicode character string. QString stores a string of 16-bit QChars, where each QChar stores one Unicode 4.0 character. Unicode is an international standard that supports most of the writing systems in use today. It is a superset of ASCII and Latin-1 (ISO 8859-1), and all the ASCII/Latin-1 characters are available at the same code positions. Behind the scenes, QString uses implicit sharing (copy-on-write) to reduce memory usage and to avoid the needless copying of data. This also helps reduce the inherent overhead of storing 16-bit characters instead of 8-bit characters. </quote> So, can I do this with confidence? const XMLCh* QtoX(const QString& s) { return reinterpret_cast<const XMLCh*>(s.constData()); } Q:Is this thing loaded? A:I don't know; pull the trigger and find out. Q:Where should I point it? Steven

1 1