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• How to emulate "-lib foo.jar" from _within_ build.xml

  - by Thorbjørn Ravn Andersen

  By specifying "-lib foo.jar" to ant I get the behaviour that the classes in foo.jar is added to the ant classloader and are available for various tasks taking a class name argument. I'd like to be able to specify the same behaviour but only from inside build.xml (so we can do this on a vanilla ant). For taskdefs we have functioning code looking like: <taskdef resource="net/sf/antcontrib/antlib.xml" description="for/foreach tasks"> <classpath> <pathelement location="${active.workspace}/ant-contrib-1.X/lib/ant-contrib.jar" /> </classpath> </taskdef> where the definition is completely provided from the ant-contrib.jar listed. What is the equivalent mechanism for the "global" ant classpath? (I have thought out that this is the way to get <javac> use ecj-3.5.jar to compile with on a JRE - http://stackoverflow.com/questions/2364006/specifying-the-eclipse-compiler-completely-from-within-build-xml - in a way compatible with ant 1.7. Better suggestions are welcome :) EDIT: It appears that the about-to-be-released version 1.0 of ant4eclipse includes ecj. This does not answer the question, but may solve my basic problem.

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• write to fifo/pipe from shell, with timeout

  - by Tim

  I have a pair of shell programs that talk over a named pipe. The reader creates the pipe when it starts, and removes it when it exits. Sometimes, the writer will attempt to write to the pipe between the time that the reader stops reading and the time that it removes the pipe. reader: while condition; do read data <$PIPE; do_stuff; done writer: echo $data >>$PIPE reader: rm $PIPE when this happens, the writer will hang forever trying to open the pipe for writing. Is there a clean way to give it a timeout, so that it won't stay hung until killed manually? I know I can do #!/bin/sh # timed_write <timeout> <file> <args> # like "echo <args> >> <file>" with a timeout TIMEOUT=$1 shift; FILENAME=$1 shift; PID=$$ (X=0; # don't do "sleep $TIMEOUT", the "kill %1" doesn't kill the sleep while [ "$X" -lt "$TIMEOUT" ]; do sleep 1; X=$(expr $X + 1); done; kill $PID) & echo "$@" >>$FILENAME kill %1 but this is kind of icky. Is there a shell builtin or command to do this more cleanly (without breaking out the C compiler)?

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• How To Get the Name of the Current Procedure/Function in Delphi (As a String)

  - by Andreas Rejbrand

  Is it possible to obtain the name of the current procedure/function as a string, within a procedure/function? I suppose there would be some "macro" that is expanded at compile-time. My scenario is this: I have a lot of procedures that are given a record and they all need to start by checking the validity of the record, and so they pass the record to a "validator procedure". The validator procedure raises an exception if the record is invalid, and I want the message of the exception to include not the name of the validator procedure, but the name of the function/procedure that called the validator procedure (naturally). That is, I have procedure ValidateStruct(const Struct: TMyStruct; const Sender: string); begin if <StructIsInvalid> then raise Exception.Create(Sender + ': Structure is invalid.'); end; and then procedure SomeProc1(const Struct: TMyStruct); begin ValidateStruct(Struct, 'SomeProc1'); ... end; ... procedure SomeProcN(const Struct: TMyStruct); begin ValidateStruct(Struct, 'SomeProcN'); ... end; It would be somewhat less error-prone if I instead could write something like procedure SomeProc1(const Struct: TMyStruct); begin ValidateStruct(Struct, {$PROCNAME}); ... end; ... procedure SomeProcN(const Struct: TMyStruct); begin ValidateStruct(Struct, {$PROCNAME}); ... end; and then each time the compiler encounters a {$PROCNAME}, it simply replaces the "macro" with the name of the current function/procedure as a string literal.

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• How to use void*

  - by Rondogiannis Aristophanes

  I am imlementing a simple merge function and I have got stuck, as the compiler gives me errors that I cannot explain. Here is my merge function: void merge(void *a, int beg, int middle, int end, int (*cmp)(const void*, const void* { std::stack<void*> first; std::stack<void*> second; for(int i = beg; i < middle; i++) { first.push(a+i); } for(int i = middle; i < end; i++) { second.push(a+i); } for(int i = beg; i < end; i++) { if(first.empty()) { void *tmp = second.top(); second.pop(); a+i = tmp; } else if(second.empty()) { void *tmp = first.top(); first.pop(); a+i = tmp; } else if(cmp(first.top(), second.top())) { void *tmp = first.top(); first.pop(); a+i = tmp; } else { void *tmp = second.top(); second.pop(); a+i = tmp; } } } And here is the error: sort.h: In function `void merge(void*, int, int, int, int (*)(const void*, const void*))': sort.h:9: error: pointer of type `void *' used in arithmetic sort.h:12: error: pointer of type `void *' used in arithmetic sort.h:19: error: pointer of type `void *' used in arithmetic sort.h:19: error: non-lvalue in assignment sort.h:23: error: pointer of type `void *' used in arithmetic sort.h:23: error: non-lvalue in assignment sort.h:27: error: pointer of type `void *' used in arithmetic sort.h:27: error: non-lvalue in assignment sort.h:31: error: pointer of type `void *' used in arithmetic sort.h:31: error: non-lvalue in assignment Can anyone help me? TIA.

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• Creating spotlight in OpenGL scene

  - by Victor Oliveira

  Im studying OpenGL and trying to create a spot light at my application. The code that Im using for my #vertex-shader is below: #:vertex-shader #{ #version 150 core in vec3 in_pos; in vec2 in_tc; out vec2 tc; glLightf(GL_LIGHT0, GL_SPOT_CUTOFF, 20.0f); GLfloat spot_direction[] = { -1.0, -1.0, 0.0 }; glLightfv(GL_LIGHT0, GL_SPOT_DIRECTION, spot_direction); glEnable(GL_LIGHT0); void main() { vec4 pos= vec4(vec3(1.0)*in_pos - vec3(1.0), 1.0); pos.z=0.0; gl_Position = pos; tc = in_tc; } } The thing is, everytime Im trying to run the code an Error that says: Type: other, Source: api, ID: 131169, Severity: low Message: Framebuffer detailed info: The driver allocated storage for renderbuffer 1. len = 157, written = 0 failed to compile vertex shader of deferred: directional info log for shader deferred: directional vertex info log for shader deferred: directional: ERROR: Unbound variable: when Specifications: Renderer: GeForce GTX 580/PCIe/SSE2 Version: 3.3.0 NVIDIA 319.17 GLSL: 3.30 NVIDIA via Cg compiler Status: Using GLEW 1.9.0 1024 x 768 OS: Linux debian I guess to create this spotlight is pretty much simple, but since Im really new to OpenGL I dont have a clue how to do it until now, even reading sources like: http://www.glprogramming.com/red/chapter05.html#name3 Read also in some place that light spots can get really hard to understand, but I cant avoid this step right now since Im following my lecture schedule. Could anybody help me?

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• Are we DELPHI, VCL or Pascal programmers?

  - by José Eduardo

  i´ve been a delphi database programmer since D2. Now i´m facing some digital imaging and 3D challenges that make me to start study OpenGL, DirectX, Color Spaces and so on. I´m really trying but nobody seems to use Delphi for this kind of stuff, just the good-old-paycheck Database programming. ok, i know that we have some very smart guys behind some clever components, some of this open-source. Is there any PhotoShop, Blender, Maya, Office, Sonar, StarCraft, Call of Dutty written in Delphi? Do i have to learn C++ to have access to zillions of books about that kind of stuff? What is the fuzz/hype behind this: int *varName = &anhoterThing? Why pointers seems to be the holy graal to this apps? I´ve downloaded MSVC++ Express and start to learn some WPF and QT integration, and i think: "Man, Delphi does this kind of stuff, with less code, less headaches, since the wheels were invented" This lead my mind to the following... Do you ever tried to write a simple notepad program using just notepad and dcc32 in Pascal/Delphi? if so embarcadero could make our beloved pascal compiler free, and sell just the ide, the vcl, the customer support ... and back to the question: Are we DELPHI, VCL or Pascal programmers?

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• Invert a string: Recursion vs iteration in javascript

  - by steweb

  Hi all, one month ago I've been interviewed by some google PTO members. One of the questions was: Invert a string recursively in js and explain the running time by big O notation this was my solution: function invert(s){ return (s.length > 1) ? s.charAt(s.length-1)+invert(s.substring(0,s.length-1)) : s; } Pretty simple, I think. And, about the big-o notation, I quickly answered O(n) as the running time depends linearly on the input. - Silence - and then, he asked me, what are the differences in terms of running time if you implement it by iteration? I replied that sometimes the compiler "translate" the recursion into iteration (some programming language course memories) so there are no differences about iteration and recursion in this case. Btw since I had no feedback about this particular question, and the interviewer didn't answer "ok" or "nope", I'd like to know if you maybe agree with me or if you can explain me whether there could be differences about the 2 kind of implementations. Thanks a lot and Regards!

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• Catching a nested-in-template exception [C++]

  - by Karol

  Hello, I have a problem with writing a catch clause for an exception that is a class nested in a template. To be more specific, I have a following definition of the template and exception: /** Generic stack implementation. Accepts std::list, std::deque and std::vector as inner container. */ template < typename T, template < typename Element, typename = std::allocator<Element> > class Container = std::deque > class stack { public: class StackEmptyException { }; ... /** Returns value from the top of the stack. Throws StackEmptyException when the stack is empty. */ T top() const; ... } I have a following template method that I want exception to catch: template <typename Stack> void testTopThrowsStackEmptyExceptionOnEmptyStack() { Stack stack; std::cout << "Testing top throws StackEmptyException on empty stack..."; try { stack.top(); } catch (Stack::StackEmptyException) { // as expected. } std::cout << "success." << std::endl; } When I compile it (-Wall, -pedantic) I get the following error: In function ‘void testTopThrowsStackEmptyExceptionOnEmptyStack()’: error: expected type-specifier error: expected unqualified-id before ‘)’ token === Build finished: 2 errors, 0 warnings === Thanks in advance for any help! What is interesting, if the stack implementation was not a template, then the compiler would accept the code as it is.

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• Procedure or function AppendDataCT has too many arguments specified

  - by salvationishere

  I am developing a C# VS 2008 / SQL Server website application. I am a newbie to ASP.NET. I am getting the above compiler error. Can you give me advice on how to fix this? Code snippet: public static string AppendDataCT(DataTable dt, Dictionary<int, string> dic) { string connString = ConfigurationManager.ConnectionStrings["AW3_string"].ConnectionString; string errorMsg; try { SqlConnection conn2 = new SqlConnection(connString); SqlCommand cmd = conn2.CreateCommand(); cmd.CommandText = "dbo.AppendDataCT"; cmd.CommandType = CommandType.StoredProcedure; cmd.Connection = conn2; SqlParameter p1, p2, p3; foreach (string s in dt.Rows[1].ItemArray) { DataRow dr = dt.Rows[1]; // second row p1 = cmd.Parameters.AddWithValue((string)dic[0], (string)dr[0]); p1.SqlDbType = SqlDbType.VarChar; p2 = cmd.Parameters.AddWithValue((string)dic[1], (string)dr[1]); p2.SqlDbType = SqlDbType.VarChar; p3 = cmd.Parameters.AddWithValue((string)dic[2], (string)dr[2]); p3.SqlDbType = SqlDbType.VarChar; } conn2.Open(); cmd.ExecuteNonQuery(); It errors on this last line here. And here is that SP: ALTER PROCEDURE [dbo].[AppendDataCT] @col1 VARCHAR(50), @col2 VARCHAR(50), @col3 VARCHAR(50) AS BEGIN SET NOCOUNT ON; DECLARE @TEMP DATETIME SET @TEMP = (SELECT CONVERT (DATETIME, @col3)) INSERT INTO Person.ContactType (Name, ModifiedDate) VALUES( @col2, @TEMP) END

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• How do I use foreach with QDomNodeList in Qt?

  - by Venemo

  Hi Everyone, I'm new to Qt and I'm learning something new every day. Currently, I'm developing a small application for my Nokia N900 in my free time. Everything is fine, I am able to compile and run Maemo applications on the device. I've just learned about the foreach keyword in Qt. (I know it is not in C++, so I didn't think about it until I accidentally stumbled upon a Qt doc that mentioned it.) So, I decided to change my quite annoying and unreadable loops to foreach, but I failed with this: QDomNodeList list = doc.lastChild().childNodes().at(1).firstChild().childNodes(); for (int x = 0; x < list.count(); x++) { QDomElement node = list.at(x).toElement(); // Do something with node } This is how I tried: foreach (QDomElement node, doc.lastChild().childNodes().at(1).firstChild().childNodes()) { // Do something with node } For some reason the above code doesn't even compile. I get cryptic error messages from the compiler. Could someone please explain to me how to get it right? If the foreach loop doesn't support QDomNodeList, is there a way of handling XML files that do support foreach?

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• SFINAE failing with enum template parameter

  - by zeroes00

  Can someone explain the following behaviour (I'm using Visual Studio 2010). header: #pragma once #include <boost\utility\enable_if.hpp> using boost::enable_if_c; enum WeekDay {MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY}; template<WeekDay DAY> typename enable_if_c< DAY==SUNDAY, bool >::type goToWork() {return false;} template<WeekDay DAY> typename enable_if_c< DAY!=SUNDAY, bool >::type goToWork() {return true;} source: bool b = goToWork<MONDAY>(); compiler this gives error C2770: invalid explicit template argument(s) for 'enable_if_c<DAY!=6,bool>::type goToWork(void)' and error C2770: invalid explicit template argument(s) for 'enable_if_c<DAY==6,bool>::type goToWork(void)' But if I change the function template parameter from the enum type WeekDay to int, it compiles fine: template<int DAY> typename enable_if_c< DAY==SUNDAY, bool >::type goToWork() {return false;} template<int DAY> typename enable_if_c< DAY!=SUNDAY, bool >::type goToWork() {return true;} Also the normal function template specialization works fine, no surprises there: template<WeekDay DAY> bool goToWork() {return true;} template<> bool goToWork<SUNDAY>() {return false;} To make things even weirder, if I change the source file to use any other WeekDay than MONDAY or TUESDAY, i.e. bool b = goToWork<THURSDAY>(); the error changes to this: error C2440: 'specialization' : cannot convert from 'int' to 'const WeekDay' Conversion to enumeration type requires an explicit cast (static_cast, C-style cast or function-style cast)

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• structure inside structure - c++ Error

  - by gamadeus

  First of all the error I am getting is of the type: Request for member 's' of struct1.struct1::struct2, which is of non class type '__u32' where: struct struct1 { struct x struct2; struct x struct3; struct x struct4; }; The usage is of the form: struct struct1 st1; st1.struct2.s = Value; Now my struct1 is: struct ip_mreq_source { struct in_addr imr_multiaddr; struct in_addr imr_sourceaddr; struct in_addr imr_interface; }; struct 'x' is in_addr Where: typedef uint32_t in_addr_t; struct in_addr { in_addr_t s_addr; }; element 's' is the element s_addr in in_addr. My detailed error coming out of g++ (GCC 4.4.3) from the Android based compiler: arm-linux-androideabi-g++ -MMD -MP -MF groupsock/GroupsockHelper.o.d.org -fpic -ffunction-sections -funwind-tables -fstack-protector -D__ARM_ARCH_5__ -D__ARM_ARCH_5T__ -D__ARM_ARCH_5E__ -D__ARM_ARCH_5TE__ -Wno-psabi -march=armv5te -mtune=xscale -msoft-float -fno-exceptions -fno-rtti -mthumb -Os -fomit-frame-pointer -fno-strict-aliasing -finline- limit=64 -Igroupsock/include -Igroupsock/../UsageEnvironment/include -Iandroid- ndk-r5b/sources/cxx-stl/system/include -Igroupsock -DANDROID -Wa,--noexecstack -DANDROID_NDK -Wall -fexceptions -O2 -DNDEBUG -g -Iandroid-8/arch-arm/usr/include -c groupsock/GroupsockHelper.cpp -o groupsock/GroupsockHelper.o && rm -f groupsock/GroupsockHelper.o.d && mv groupsock/GroupsockHelper.o.d.org groupsock/GroupsockHelper.o.d groupsock/GroupsockHelper.cpp: In function 'Boolean socketJoinGroupSSM(UsageEnvironment&, int, netAddressBits, netAddressBits)': groupsock/GroupsockHelper.cpp:427: error: request for member 's_addr' in 'imr.ip_mreq_source::imr_multiaddr', which is of non-class type '__u32' groupsock/GroupsockHelper.cpp:428: error: request for member 's_addr' in 'imr.ip_mreq_source::imr_sourceaddr', which is of non-class type '__u32' groupsock/GroupsockHelper.cpp:429: error: request for member 's_addr' in 'imr.ip_mreq_source::imr_interface', which is of non-class type '__u32' I am not sure what is causing the error. Any pointers would be great - no pun intended. Thanks

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• With PascalMock how do I mock a method with an untyped out parameter and an open array parameter?

  - by Oliver Giesen

  I'm currently in the process of getting started with unit testing and mocking for good and I stumbled over the following method that I can't seem to fabricate a working mock implementation for: function GetInstance(const AIID: TGUID; out AInstance; const AArgs: array of const; const AContextID: TImplContextID = CID_DEFAULT): Boolean; (TImplContextID is just an alias for Integer) I thought it would have to look something like this: function TImplementationProviderMock.GetInstance( const AIID: TGUID; out AInstance; const AArgs: array of const; const AContextID: TImplContextID): Boolean; begin Result := AddCall('GetInstance') .WithParams([@AIID, AContextID]) .ReturnsOutParams([AInstance]) .ReturnValue; end; But the compiler complains about the .ReturnsOutParams([AInstance]) saying "Bad argument type in variable type array constructor.". Also I haven't found a way to specify the open array parameter AArgs at all. Also, is using the @-notation for the TGUID-typed parameter the right way to go? Is it possible to mock this method with the current version of PascalMock at all?

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• iphone - using NSInvocation: constant value

  - by Mike

  I am dealing with an old iPhone OS 2.x project and I want to keep compatibility, while designing for 3.x. I am using NSInvocation, is a code like this NSInvocation* invoc = [NSInvocation invocationWithMethodSignature: [cell methodSignatureForSelector: @selector(initWithStyle:reuseIdentifier:)]]; [invoc setTarget:cell]; [invoc setSelector:@selector(initWithStyle:reuseIdentifier:)]; int arg2 = UITableViewCellStyleDefault; //???? [invoc setArgument:&arg2 atIndex:2]; [invoc setArgument:&identificadorNormal atIndex:3]; [invoc invoke]; to call 3.0 APIs on 2.0. I am having a problem on the line I marked with question marks. The problem there is that I am trying to assing to arg2, a constant that has not been defined in OS 2.0. As everything with NSInvocation is to do stuff indirectly to avoid compiler errors, how do I set this constant to a variable in an indirect way? Some sort of performSelector "assign value to variable"... is that possible? thanks for any help.

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• Use of var keyword in C#

  - by kronoz

  After discussion with colleagues regarding the use of the 'var' keyword in C# 3 I wondered what people's opinions were on the appropriate uses of type inference via var? For example I rather lazily used var in questionable circumstances, e.g.:- foreach(var item in someList) { // ... } // Type of 'item' not clear. var something = someObject.SomeProperty; // Type of 'something' not clear. var something = someMethod(); // Type of 'something' not clear. More legitimate uses of var are as follows:- var l = new List<string>(); // Obvious what l will be. var s = new SomeClass(); // Obvious what s will be. Interestingly LINQ seems to be a bit of a grey area, e.g.:- var results = from r in dataContext.SomeTable select r; // Not *entirely clear* what results will be here. It's clear what results will be in that it will be a type which implements IEnumerable, however it isn't entirely obvious in the same way a var declaring a new object is. It's even worse when it comes to LINQ to objects, e.g.:- var results = from item in someList where item != 3 select item; This is no better than the equivilent foreach(var item in someList) { // ... } equivilent. There is a real concern about type safety here - for example if we were to place the results of that query into an overloaded method that accepted IEnumerable<int> and IEnumerable<double> the caller might inadvertently pass in the wrong type. Edit - var does maintain strong typing but the question is really whether it's dangerous for the type to not be immediately apparent on definition, something which is magnified when overloads mean compiler errors might not be issued when you unintentionally pass the wrong type to a method. Related Question: http://stackoverflow.com/questions/633474/c-do-you-use-var

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• Writing fortran robust and "modern" code

  - by Blklight

  In some scientific environments, you often cannot go without FORTRAN as most of the developers only know that idiom, and there is lot of legacy code and related experience. And frankly, there are not many other cross-platform options for high performance programming ( C++ would do the task, but the syntax, zero-starting arrays, and pointers are too much for most engineers ;-) ). I'm a C++ guy but I'm stuck with some F90 projects. So, let's assume a new project must use FORTRAN (F90), but I want to build the most modern software architecture out of it. while being compatible with most "recent" compilers (intel ifort, but also including sun/HP/IBM own compilers) So I'm thinking of imposing: global variable forbidden, no gotos, no jump labels, "implicit none", etc. "object-oriented programming" (modules with datatypes + related subroutines) modular/reusable functions, well documented, reusable libraries assertions/preconditions/invariants (implemented using preprocessor statements) unit tests for all (most) subroutines and "objects" an intense "debug mode" (#ifdef DEBUG) with more checks and all possible Intel compiler checks possible (array bounds, subroutine interfaces, etc.) uniform and enforced legible coding style, using code processing tools C stubs/wrappers for libpthread, libDL (and eventually GPU kernels, etc.) C/C++ implementation of utility functions (strings, file operations, sockets, memory alloc/dealloc reference counting for debug mode, etc.) ( This may all seem "evident" modern programming assumptions, but in a legacy fortran world, most of these are big changes in the typical programmer workflow ) The goal with all that is to have trustworthy, maintainable and modular code. Whereas, in typical fortran, modularity is often not a primary goal, and code is trustworthy only if the original developer was very clever, and the code was not changed since then ! (i'm a bit joking here, but not much) I searched around for references about object-oriented fortran, programming-by-contract (assertions/preconditions/etc.), and found only ugly and outdated documents, syntaxes and papers done by people with no large-scale project involvement, and dead projects. Any good URL, advice, reference paper/books on the subject?

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• Can't set Visible attribute in ASP.NET Panels

  - by RichW

  I am having trouble with visible attribute of an ASP.NET Panel control. I have a page that calls a database table and returns the results in a datagrid. Requirements If some of the returned values are null I need to hide the image that's next to it. I am using a Panel to determine whether to hide or show the image but am having trouble with the statement: visible='<%# Eval("addr1") <> DBNull.Value %>' I have tried these as well: visible='<%# Eval("addr1") <> DBNull.Value %>' visible='<%# IIf(Eval("addr1") Is DbNull.Value, "False","True") %>' Code is below: <asp:TemplateField > <ItemTemplate> <%# Eval("Name")%> <p> <asp:Panel runat="server" ID="Panel1" visible='<%# Eval("addr1") <> DBNull.Value %>'> <asp:Image Id="imgHouse" runat="server" AlternateText="Address" SkinId="imgHouse"/> </asp:Panel> <%# Eval("addr1") %><p> </ItemTemplate> </asp:TemplateField> What am I doing wrong? Edit If I use visible='<%# IIf(Eval("addr1") Is DbNull.Value, "False","True") %>' I get the following error: Compiler Error Message: CS1026: ) expected

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• What are the benefits of the PHP the different PHP compression libraries?

  - by Christopher W. Allen-Poole

  I've been looking into ways to compress PHP libraries, and I've found several libraries which might be useful, but I really don't know much about them. I've specifically been reading about bcompiler and PHAR libraries. Is there any performance benefit in either of these? Are there any "gotchas" I need to watch out for? What are the relative benefits? Do either of them add to/detract from performance? I'm also interested in learning of other libs which might be out there which are not obvious in the documentation? As an aside, does anyone happen to know whether these work more like zip files which just happen to have the code in there, or if they operate more like Python's pre-compiling which actually runs a pseudo-compiler? ======================= EDIT ======================= I've been asked, "What are you trying to accomplish?" Well, I suppose the answer is that this is all hypothetical. It is a combination of these: What if my pet project becomes the most popular web project on earth and I want to distribute it quickly and easily? (hay, a man can dream, right?) It also seems if using PHAR can be done easily, it would be the best way to create a subversion snapshot. Python has this really cool pre-compiling policy, I wonder if PHP has something like that? These libraries seem to do something similar. Will they do that? Hey, these libraries seem pretty neat, but I'd like clarification on the differences as they seem to do the same thing

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• question/problem regarding assigning an array of char *

  - by Fantastic Fourier

  Hi I'm working with C and I have a question about assigning pointers. struct foo { int _bar; char * _car[MAXINT]; // this is meant to be an array of char * so that it can hold pointers to names of cars } int foofunc (void * arg) { int bar; char * car[MAXINT]; struct foo thing = (struct foo *) arg; bar = arg->_bar; // this works fine car = arg->_car; // this gives compiler errors of incompatible types in assignment } car and _car have same declaration so why am I getting an error about incompatible types? My guess is that it has something to do with them being pointers (because they are pointers to arrays of char *, right?) but I don't see why that is a problem. when i declared char * car; instead of char * car[MAXINT]; it compiles fine. but I don't see how that would be useful to me later when I need to access certain info using index, it would be very annoying to access that info later. in fact, I'm not even sure if I am going about the right way, maybe there is a better way to store a bunch of strings instead of using array of char *?

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• Why does autoboxing in Java allow me to have 3 possible values for a boolean?

  - by John

  Reference: http://java.sun.com/j2se/1.5.0/docs/guide/language/autoboxing.html If your program tries to autounbox null, it will throw a NullPointerException. javac will give you a compile-time error if you try to assign null to a boolean. makes sense. assigning null to a Boolean is a-ok though. also makes sense, i guess. but let's think about the fact that you'll get a NPE when trying to autounbox null. what this means is that you can't safely perform boolean operations on Booleans without null-checking or exception handling. same goes for doing math operations on an Integer. for a long time, i was a fan of autoboxing in java1.5+ because I thought it got java closer to be truly object-oriented. but, after running into this problem last night, i gotta say that i think this sucks. the compiler giving me an error when I'm trying to do stuff with an uninitialized primitive is a good thing. I think I may be misunderstanding the point of autoboxing, but at the same time I will never accept that a boolean should be able to have 3 values. can anyone explain this? what am i not getting?

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• How to force the build to be out of date, when a text file is modified?

  - by demoncodemonkey

  The Scenario My project has a post-build phase set up to run a batch file, which reads a text file "version.txt". The batch file uses the information in version.txt to inject the DLL with a version block using this tool. The version.txt is included in my project to make it easy to modify. It looks a bit like this: @set #Description="TankFace Utility Library" @set #FileVersion="0.1.2.0" @set #Comments="" Basically the batch file renames this file to version.bat, calls it, then renames it back to version.txt afterwards. The Problem When I modify version.txt (e.g. to increment the file version), and then press F7, the build is not seen as out-of-date, so the post-build step is not executed, so the DLL's version doesn't get updated. I really want to include the .txt file as an input to the build, but without anything actually trying to use it. If I #include the .txt file from a CPP file in the project, the compiler fails because it obviously doesn't understand what "@set" means. If I add /* ... */ comments around the @set commands, then the batch file has some syntax errors but eventually succeeds. But this is a poor solution I think. So... how would you do it?

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• Ignore LD_LIBRARY_PATH and stick with library given through -rpath at link time

  - by roe

  I'm sitting in an environment which I have no real control over (it's not just me, so basically, I can't change the environment or it won't work for anyone else), the only thing I can affect is how the binary is built. My problem is, the environment specifies an LD_LIBRARY_PATH containing a libstdc++ which is not compatible with the compiler being used. I tried compiling it statically, but that doesn't seem possible for g++ (version 4.2.3, seems to have been work done in this direction in later versions though which are not available, -static-libstdc++ or something like that). Now I've arrived at using rpath to bake the absolute path name into the executable (would work, all machines it's supposed to run on are identical). Unfortunately it appears as though LD_LIBRARY_PATH takes precedence over rpath (resetting LD_LIBRARY_PATH confirmed that it's able to find the library, but as stated above, LD_LIBRARY_PATH will be set for everyone, and I cannot change that). Is there any way I can make rpath take precedence over LD_LIBRARY_PATH, or are there any other possible solutions to my problem? Note that I'm talking about dynamic linking at runtime, I am able to control the command line at compile and link time. Thanks.

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• Why doesen't it work to write this NSMutableArray to a plist?

  - by Emil

  edited. Hey, I am trying to write an NSMutableArray to a plist. The compiler does not show any errors, but it does not write to the plist anyway. I have tried this on a real device too, not just the Simulator. Basically, what this code does, is that when you click the accessoryView of a UITableViewCell, it gets the indexPath pressed, edits an NSMutableArray and tries to write that NSMutableArray to a plist. It then reloads the arrays mentioned (from multiple plists) and reloads the data in a UITableView from the arrays. Code: NSIndexPath *indexPath = [table indexPathForRowAtPoint:[[[event touchesForView:sender] anyObject] locationInView:table]]; [arrayFav removeObjectAtIndex:[arrayFav indexOfObject:[NSNumber numberWithInt:[[arraySub objectAtIndex:indexPath.row] intValue]]]]; NSString *rootPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0]; NSString *plistPath = [rootPath stringByAppendingPathComponent:@"arrayFav.plist"]; NSLog(@"%@ - %@", rootPath, plistPath); [arrayFav writeToFile:plistPath atomically:YES]; // Reloads data into the arrays [self loadDataFromPlists]; // Reloads data in tableView from arrays [tableFarts reloadData];

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• How close can I get C# to the performance of C++ for small intensive tasks?

  - by SLC

  I was thinking about the speed difference of C++ to C# being mostly about C# compiling to byte-code that is taken in by the JIT compiler (is that correct?) and all the checks C# does. I notice that it is possible to turn a lot of these functions off, both in the compile options, and possibly through using the unsafe keyword as unsafe code is not verifiable by the common language runtime. Therefore if you were to write a simple console application in both languages, that flipped an imaginary coin an infinite number of times and displayed the results to the screen every 10,000 or so iterations, how much speed difference would there be? I chose this because it's a very simple program. I'd like to test this but I don't know C++ or have the tools to compile it. This is my C# version though: static void Main(string[] args) { unsafe { Random rnd = new Random(); int heads = 0, tails = 0; while (true) { if (rnd.NextDouble() > 0.5) heads++; else tails++; if ((heads + tails) % 1000000 == 0) Console.WriteLine("Heads: {0} Tails: {1}", heads, tails); } } } Is the difference enough to warrant deliberately compiling sections of code "unsafe" or into DLLs that do not have some of the compile options like overflow checking enabled? Or does it go the other way, where it would be beneficial to compile sections in C++? I'm sure interop speed comes into play too then. To avoid subjectivity, I reiterate the specific parts of this question as: Does C# have a performance boost from using unsafe code? Do the compile options such as disabling overflow checking boost performance, and do they affect unsafe code? Would the program above be faster in C++ or negligably different? Is it worth compiling long intensive number-crunching tasks in a language such as C++ or using /unsafe for a bonus? Less subjectively, could I complete an intensive operation faster by doing this?

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• How do I tell gcc to relax its restrictions on typecasting when calling a C function from C++?

  - by Daryl Spitzer

  I'm trying to use Cmockery to mock C functions called from C++ code. Because the SUT is in C++, my tests need to be in C++. When I use the Cmockery expect_string() macro like this: expect_string(mock_function, url, "Foo"); I get: my_tests.cpp: In function ‘void test_some_stuff(void**)’: my_tests.cpp:72: error: invalid conversion from ‘void*’ to ‘const char*’ my_tests.cpp:72: error: initializing argument 5 of ‘void _expect_string(const char*, const char*, const char*, int, const char*, int)’ I see in cmockery.h that expect_string is defined: #define expect_string(function, parameter, string) \ expect_string_count(function, parameter, string, 1) #define expect_string_count(function, parameter, string, count) \ _expect_string(#function, #parameter, __FILE__, __LINE__, (void*)string, \ count) And here's the prototype for _expect_string (from cmockery.h): void _expect_string( const char* const function, const char* const parameter, const char* const file, const int line, const char* string, const int count); I believe the problem is that I'm compiling C code as C++, so the C++ compiler is objecting to (void*)string in the expect_string_count macro being passed as the const char* string parameter to the _expect_string() function. I've already used extern "C" around the cmockery.h include in my_tests.cpp like this: extern "C" { #include <cmockery.h> } ...in order to get around name-mangling problems. (See "How do I compile and link C++ code with compiled C code?") Is there a command-line option or some other means of telling g++ how to relax its restrictions on typecasting from my test's C++ code to the C function in cmockery.c? This is the command I'm currently using to build my_tests.cpp: g++ -m32 -I ../cmockery-0.1.2 -c my_tests.cpp -o $(obj_dir)/my_tests.o

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