definition - Page 130 - Developer IT

dynamic char array sizing

- by droseman

Hello, In my application, I have a char array defined which can take one of three options: "okay", "high", "low" which are then sent down a serial port to a remote device. I currently have the array sized to take the 4 character words plus carriage return and line feed, but when I have to send "low" I get a null character in the strings, which I am concerned would confuse the host terminal. array definition char mod1_status_char[6] = {'0','0','0','0','0','0'}; char mod2_status_char[6] = {'0','0','0','0','0','0'}; char mod3_status_char[6] = {'0','0','0','0','0','0'}; sample of switch case statement: void DCOKStatus(uint8_t *ptr_status) { uint8_t status = *ptr_status; switch (status) { case 0x00: strcpy(mod1_status_char, "okay"); strcpy(mod2_status_char, "okay"); strcpy(mod3_status_char, "okay"); break; case 0x10: strcpy(mod1_status_char, "okay"); strcpy(mod2_status_char, "okay"); strcpy(mod3_status_char, "low"); break; } This is the struct which makes the message string to send strcpy(MsgStatus_on.descriptor_msg, "$psu_"); MsgStatus_on.address01 = hex_addr[0]; MsgStatus_on.address02 = hex_addr[1]; MsgStatus_on.space01 = 0x20; strcpy(MsgStatus_on.cmdmsg01, "op_en op1_"); strcpy(MsgStatus_on.statusmsg01, mod1_status_char); MsgStatus_on.space02 = 0x20; strcpy(MsgStatus_on.cmdmsg02, "op2_"); strcpy(MsgStatus_on.statusmsg02, mod2_status_char); MsgStatus_on.space03 = 0x20; strcpy(MsgStatus_on.cmdmsg03, "op3_"); strcpy(MsgStatus_on.statusmsg03, mod3_status_char); MsgStatus_on.CR = 0x0D; MsgStatus_on.LF = 0x0A; and this sends the message void USARTWrite(char *object, uint32_t size) { GPIO_SetBits(GPIOB, GPIO_Pin_1); char *byte; for (byte = object; size--; ++byte) { USART_SendData(USART1,*byte); } Would anyone be able to suggest a good approach to dynamically size the array to one character shorter when I need to send "low"? Thanks

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quartz: preventing concurrent instances of a job in jobs.xml

- by Jason S

This should be really easy. I'm using Quartz running under Apache Tomcat 6.0.18, and I have a jobs.xml file which sets up my scheduled job that runs every minute. What I would like to do, is if the job is still running when the next trigger time rolls around, I don't want to start a new job, so I can let the old instance complete. Is there a way to specify this in jobs.xml (prevent concurrent instances)? If not, is there a way I can share access to an in-memory singleton within my application's Job implementation (is this through the JobExecutionContext?) so I can handle the concurrency myself? (and detect if a previous instance is running) update: After floundering around in the docs, here's a couple of approaches I am considering, but either don't know how to get them to work, or there are problems. Use StatefulJob. This prevents concurrent access... but I'm not sure what other side-effects would occur if I use it, also I want to avoid the following situation: Suppose trigger times would be every minute, i.e. trigger#0 = at time 0, trigger #1 = 60000msec, #2 = 120000, #3 = 180000, etc. and the trigger#0 at time 0 fires my job which takes 130000msec. With a plain Job, this would execute triggers #1 and #2 while job trigger #0 is still running. With a StatefulJob, this would execute triggers #1 and #2 in order, immediately after #0 finishes at 130000. I don't want that, I want #1 and #2 not to run and the next trigger that runs a job should take place at #3 (180000msec). So I still have to do something else with StatefulJob to get it to work the way I want, so I don't see much of an advantage to using it. Use a TriggerListener to return true from vetoJobExecution(). Although implementing the interface seems straightforward, I have to figure out how to setup one instance of a TriggerListener declaratively. Can't find the docs for the xml file. Use a static shared thread-safe object (e.g. a semaphore or whatever) owned by my class that implements Job. I don't like the idea of using singletons via the static keyword under Tomcat/Quartz, not sure if there are side effects. Also I really don't want them to be true singletons, just something that is associated with a particular job definition. Implement my own Trigger which extends SimpleTrigger and contains shared state that could run its own TriggerListener. Again, I don't know how to setup the XML file to use this trigger rather than the standard <trigger><simple>...</simple></trigger>.

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Where to put a glossary of important terms and patterns in documentation?

- by Tetha

Greetings. I want to document certain patterns in the code in order to build up a consistent terminology (in order to easen communication about the software). I am, however, unsure, where to define the terms given. In order to get on the same level, an example: I have a code generator. This code generator receives a certain InputStructure from the Parser (yes, the name InputStructure might be less than ideal). This InputStructure is then transformed into various subsequent datastructures (like an abstract description of the validation process). Each of these datastructures can be either transformed into another value of the same datastructure or it can be transformed into the next datastructure. This should sound like Pipes and Filters to some degree. Given this, I call an operation which takes a datastructures and constructs a value of the same datastructure a transformation, while I call an operation which takes a datastructure and produces a different follow-up datastructure a derivation. The final step of deriving a string containing code is called emitting. (So, overall, the codegenerator takes the input-structure and transforms, transforms, derives, transforms, derives and finally emits). I think emphasizing these terms will be benefitial in communications, because then it is easy to talk about things. If you hear "transformation", you know "Ok, I only need to think about these two datastructures", if you hear "emitting", you know "Ok, I only need to know this datastructure and the target language.". However, where do I document these patterns? The current code base uses visitors and offers classes called like ValidatorTransformationBase<ResultType> (or InputStructureTransformationBase<ResultType>, and so one and so on). I do not really want to add the definition of such terms to the interfaces, because in that case, I'd have to repeat myself on each and every interface, which clearly violates DRY. I am considering to emphasize the distinction between Transformations and Derivations by adding further interfaces (I would have to think about a better name for the TransformationBase-classes, but then I could do thinks like ValidatorTransformation extends ValidatorTransformationBase<Validator>, or ValidatorDerivationFromInputStructure extends InputStructureTransformation<Validator>). I also think I should add a custom page to the doxygen documentation already existing, as in "Glossary" or "Architecture Principles", which contains such principles. The only disadvantage of this would be that a contributor will need to find this page in order to actually learn about this. Am I missing possibilities or am I judging something wrong here in your opinion? -- Regards, Tetha

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.NET: Interface Problem VB.net Getter Only Interface

- by snmcdonald

Why does an interface override a class definition and violate class encapsulation? I have included two samples below, one in C# and one in VB.net? VB.net Module Module1 Sub Main() Dim testInterface As ITest = New TestMe Console.WriteLine(testInterface.Testable) ''// Prints False testInterface.Testable = True ''// Access to Private!!! Console.WriteLine(testInterface.Testable) ''// Prints True Dim testClass As TestMe = New TestMe Console.WriteLine(testClass.Testable) ''// Prints False ''//testClass.Testable = True ''// Compile Error Console.WriteLine(testClass.Testable) ''// Prints False End Sub End Module Public Class TestMe : Implements ITest Private m_testable As Boolean = False Public Property Testable As Boolean Implements ITest.Testable Get Return m_testable End Get Private Set(ByVal value As Boolean) m_testable = value End Set End Property End Class Interface ITest Property Testable As Boolean End Interface C# using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace InterfaceCSTest { class Program { static void Main(string[] args) { ITest testInterface = new TestMe(); Console.WriteLine(testInterface.Testable); testInterface.Testable = true; Console.WriteLine(testInterface.Testable); TestMe testClass = new TestMe(); Console.WriteLine(testClass.Testable); //testClass.Testable = true; Console.WriteLine(testClass.Testable); } } class TestMe : ITest { private bool m_testable = false; public bool Testable { get { return m_testable; } private set { m_testable = value; } } } interface ITest { bool Testable { get; set; } } } More Specifically How do I implement a interface in VB.net that will allow for a private setter. For example in C# I can declare: class TestMe : ITest { private bool m_testable = false; public bool Testable { get { return m_testable; } private set //No Compile Error here! { m_testable = value; } } } interface ITest { bool Testable { get; } } However, if I declare an interface property as readonly in VB.net I cannot create a setter. If I create a VB.net interface as just a plain old property then interface declarations will violate my encapsulation. Public Class TestMe : Implements ITest Private m_testable As Boolean = False Public ReadOnly Property Testable As Boolean Implements ITest.Testable Get Return m_testable End Get Private Set(ByVal value As Boolean) ''//Compile Error m_testable = value End Set End Property End Class Interface ITest ReadOnly Property Testable As Boolean End Interface So my question is, how do I define a getter only Interface in VB.net with proper encapsulation? I figured the first example would have been the best method. However, it appears as if interface definitions overrule class definitions. So I tried to create a getter only (Readonly) property like in C# but it does not work for VB.net. Maybe this is just a limitation of the language?

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ActiveMQ 5.2.0 + REST + HTTP POST = java.lang.OutOfMemoryError

- by Bruce Loth

First off, I am a newbie when it comes to JMS & ActiveMQ. I have been looking into a messaging solution to serve as middleware for a message producer that will insert XML messages into a queue via HTTP POST. The producer is an existing system written in C++ that cannot be modified (so Java and the C++ API are out). Using the "demo" examples and some trial and error, I have cobbled together a working example of what I want to do (on a windows box). The web.xml I configured in a test directory under "webapps" specifies that the HTTP POST messages received from the producer are to be handled by the MessageServlet. I added a line for the text app in "activemq.xml" ('ow' is the test app dir): I created a test script to "insert" messages into the queue which works well. The problem I am running into is that it as I continue to insert messages via REST/HTTP POST, the memory consumption and thread count used by ActiveMQ continues to rise (It happens when I have timely consumers as well as slow or non-existent consumers). When memory consumption gets around 250MB's and the thread count exceeds 5000 (as shown in windows task manager), ActiveMQ crashes and I see this in the log: Exception in thread "ActiveMQ Transport Initiator: vm://localhost#3564" java.lang.OutOfMemoryError: unable to create new native thread It is as if Jetty is spawning a new thread to handle each HTTP POST and the thread never dies. I did look at this page: http://activemq.apache.org/javalangoutofmemory.html and tried but that didn't fix the problem (although I didn't fully understand the implications of the change either). Does anyone have any ideas? Thanks! Bruce Loth PS - I included the "test message producer" python script below for what it is worth. I created batches of 100 messages and continued to run the script manually from the command line while watching the memory consumption and thread count of ActiveMQ in task manager. def foo(): import httplib, urllib body = "<?xml version='1.0' encoding='UTF-8'?>\n \ <ROOT>\n \ [snip: xml deleted to save space] </ROOT>" headers = {"content-type": "text/xml", "content-length": str(len(body))} conn = httplib.HTTPConnection("127.0.0.1:8161") conn.request("POST", "/ow/message/RDRCP_Inbox?type=queue", body, headers) response = conn.getresponse() print response.status, response.reason data = response.read() conn.close() ## end method definition ## Begin test code count = 0; while(count < 100): # Test with batches of 100 msgs count += 1 foo()

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Can I append to a preprocessor macro?

- by JCSalomon

Is there any way in standard C—or with GNU extensions—to append stuff to a macro definition? E.g., given a macro defined as #define quux_list X(foo) X(bar) can I append X(bas) so that it now expands as if I’d defined it #define quux_list X(foo) X(bar) X(bas)? I’m playing with discriminated/tagged unions along these lines: struct quux_foo { int x; }; struct quux_bar { char *s; }; struct quux_bas { void *p; }; enum quux_type {quux_foo, quux_bar, quux_bas}; struct quux { enum quux_type type; union { struct quux_foo foo; struct quux_bar bar; struct quux_bas bas; } t; }; I figure this is a good place for the X-macro. If I define a macro #define quux_table X(foo) X(bar) X(bas) the enumeration & structure can be defined thus, and never get out of sync: #define X(t) quux_ ## t, enum quux_type {quux_table}; #undef X #define X(t) struct quux_ ## t t; struct quux { enum quux_type type; union {quux_table} t; }; #undef X Of course, the quux_* structures can get out of sync, so I’d like to do something like this, only legally: struct quux_foo { int x; }; #define quux_table quux_table X(foo) struct quux_bar { char *s; }; #define quux_table quux_table X(bar) struct quux_bas { void *p; }; #define quux_table quux_table X(bas) (Well, what I really want to be able to do is something like member_struct(quux, foo) { int x; }; but I’m well aware that macros cannot be (re)defined from within macros.) Anyhow, that’s my motivating example. Is there a way to accomplish this? Boost.Preprocessor examples are fine, if you can show me how to make the X-macro technique work with that library.

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Coldfusion Components:- The argument passed to the function is not of type numeric

- by salim.vali

Hi I have a simple form form.cfm:- <cfset Registr = createObject("component", "forms.Registr") /> <cfset setFoo = createObject('component','forms.Registr).putNUsr(username,password,rating) /> <form name="regFrm" action="#cgi.script_name#" method="post" onsubmit="submitform();" > <tr><td>Username:</td> <td><input type="text" name=" Username" value="#form. Username#" ></td></tr> <tr><td>Password:</td> <td><input class="" type="password" name="password" value="#form.password#" ></td></tr> <tr><td>Rate:</td> <select name="rating" > <option value="" ></option> <cfloop query="qGetReting"> <option value="#rating_id#" <cfif form. rating eq prof_id>selected</cfif> >#rating#</option> </cfloop> </select> </td> </tr> </form> Now there is this cfc called Registr.cfc in the "forms" folder which has an insert-function called 'putNUsr'the code for 'Registr.cfc' is as follows. <cfcomponent> <cffunction name="putNUsr" returntype="void" displayname="" output="no"> <cfargument name="password" type="string" required="true"> <cfargument name="rating" type="numeric" required="true"> <cfargument name="username" type="string" required="true"> <cfquery datasource="#application.xyz#" name="q_putNUsr"> insert into users (username , password , rating) values( <cfqueryparam value="#arguments. username#" cfsqltype="CF_SQL_VARCHAR" />, <cfqueryparam value="#arguments.password#" cfsqltype="CF_SQL_VARCHAR" />, <cfqueryparam value="#arguments.rating#" cfsqltype="CF_SQL_INTEGER" ) </cfquery> </cffunction> </cfcomponent> I am able to populate the DB with the data if I do not use the form field "rating" which is numeric. Else i am getting the error as follows:- The RATING argument passed to the putNUsr function is not of type numeric. If the component name is specified as a type of this argument, it is possible that either a definition file for the component cannot be found or is not accessible. KINDLY HELP -S Vali

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Is there any reasonable use of a function returning an anonymous struct?

- by Akanksh

Here is an (artificial) example of using a function that returns an anonymous struct and does "something" useful: #include <iostream> template<typename T> T* func( T* t, float a, float b ) { if(!t) { t = new T; t->a = a; t->b = b; } else { t->a += a; t->b += b; } return t; } struct { float a, b; }* foo(float a, float b) { if(a==0) return 0; return func(foo(a-1,b), a, b); } int main() { std::cout << foo(5,6)->a << std::endl; std::cout << foo(5,6)->b << std::endl; void* v = (void*)(foo(5,6)); float* f = (float*)(v); //[1] delete f now because I know struct is floats only. std::cout << f[0] << std::endl; std::cout << f[1] << std::endl; delete[] f; return 0; } There are a few points I would like to discuss: As is apparent, this code leaks, is there anyway I can NOT leak without knowing what the underlying struct definition is? see Comment [1]. I have to return a pointer to an anonymous struct so I can create an instance of the object within the templatized function func, can I do something similar without returning a pointer? I guess the most important, is there ANY (real-world) use for this at all? As the example given above leaks and is admittedly contrived. By the way, what the function foo(a,b) does is, to return a struct containing two numbers, the sum of all numbers from 1 to a and the product of a and b. EDIT: Maybe the line new T could use a boost::shared_ptr somehow to avoid leaks, but I haven't tried that. Would that work?

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Fread binary file dynamic size string [C]

- by Blackbinary

I've been working on this assignment, where I need to read in "records" and write them to a file, and then have the ability to read/find them later. On each run of the program, the user can decide to write a new record, or read an old record (either by Name or #) The file is binary, here is its definition: typedef struct{ char * name; char * address; short addressLength, nameLength; int phoneNumber; }employeeRecord; employeeRecord record; The way the program works, it will store the structure, then the name, then the address. Name and address are dynamically allocated, which is why it is necessary to read the structure first to find the size of the name and address, allocate memory for them, then read them into that memory. For debugging purposes I have two programs at the moment. I have my file writing program, and file reading. My actual problem is this, when I read a file I have written, i read in the structure, print out the phone # to make sure it works (which works fine), and then fread the name (now being able to use record.nameLength which reports the proper value too). Fread however, does not return a usable name, it returns blank. I see two problems, either I haven't written the name to the file correctly, or I haven't read it in correctly. Here is how i write to the file: where fp is the file pointer. record.name is a proper value, so is record.nameLength. Also i am writing the name including the null terminator. (e.g. 'Jack\0') fwrite(&record,sizeof record,1,fp); fwrite(record.name,sizeof(char),record.nameLength,fp); fwrite(record.address,sizeof(char),record.addressLength,fp); And i then close the file. here is how i read the file: fp = fopen("employeeRecord","r"); fread(&record,sizeof record,1,fp); printf("Number: %d\n",record.phoneNumber); char *nameString = malloc(sizeof(char)*record.nameLength); printf("\nName Length: %d",record.nameLength); fread(nameString,sizeof(char),record.nameLength,fp); printf("\nName: %s",nameString); Notice there is some debug stuff in there (name length and number, both of which are correct). So i know the file opened properly, and I can use the name length fine. Why then is my output blank, or a newline, or something like that? (The output is just Name: with nothing after it, and program finishes just fine) Thanks for the help.

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XSD sequence shows as abiguous!

- by Tim C

I have an XSD which was transformed from a RELAX NG schema with a few errors I am trying to fix. The big issue I have it with the following <xs:element name="list"> <xs:complexType> <xs:sequence> <xs:choice> <xs:sequence> <xs:element minOccurs="0" ref="preamble"/> <xs:element minOccurs="0" ref="title"/> </xs:sequence> <xs:sequence> <xs:element minOccurs="0" ref="title"/> <xs:element minOccurs="0" ref="preamble"/> </xs:sequence> </xs:choice> <xs:group maxOccurs="unbounded" ref="block-selectionListItem"/> </xs:sequence> <xs:attributeGroup ref="attlist-selectionList"/> </xs:complexType> </xs:element> As you can see the xs:choice block allows you to pick between two xs:sequence blocks. Seems to make sense except that Visual Studio gives the following warning on the second <xs:element minOccurs="0" ref="title/> element which is throwing everything off: Multiple definition of element 'title' causes the content model to become ambiguous. A content model must be formed such that during validation of an element information item sequence, the particle contained directly, indirectly or implicitly therein with which to attempt to validate each item in the sequence in turn can be uniquely determined without examining the content or attributes of that item, and without any information about the items in the remainder of the sequence. Because you can only choose one I do not see how this is ambiguous. Any help would be greatly appreciated! Edit: To be a bit more concise here are the possible outputs of the XML that would validate with this schema: <list> <preamble>My Preamble</preamble> <title>My Title</title> </list> or: <list> <title>My Title</title> <preamble>My Preamble</preamble> </list> As you can see it can be either one way or the other but not both. Also you could just have a title or a preamble and not both.

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Hibernate + Spring : cascade deletion ignoring non-nullable constraints

- by E.Benoît

Hello, I seem to be having one weird problem with some Hibernate data classes. In a very specific case, deleting an object should fail due to existing, non-nullable relations - however it does not. The strangest part is that a few other classes related to the same definition behave appropriately. I'm using HSQLDB 1.8.0.10, Hibernate 3.5.0 (final) and Spring 3.0.2. The Hibernate properties are set so that batch updates are disabled. The class whose instances are being deleted is: @Entity( name = "users.Credentials" ) @Table( name = "credentials" , schema = "users" ) public class Credentials extends ModelBase { private static final long serialVersionUID = 1L; /* Some basic fields here */ /** Administrator credentials, if any */ @OneToOne( mappedBy = "credentials" , fetch = FetchType.LAZY ) public AdminCredentials adminCredentials; /** Active account data */ @OneToOne( mappedBy = "credentials" , fetch = FetchType.LAZY ) public Account activeAccount; /* Some more reverse relations here */ } (ModelBase is a class that simply declares a Long field named "id" as being automatically generated) The Account class, which is one for which constraints work, looks like this: @Entity( name = "users.Account" ) @Table( name = "accounts" , schema = "users" ) public class Account extends ModelBase { private static final long serialVersionUID = 1L; /** Credentials the account is linked to */ @OneToOne( optional = false ) @JoinColumn( name = "credentials_id" , referencedColumnName = "id" , nullable = false , updatable = false ) public Credentials credentials; /* Some more fields here */ } And here is the AdminCredentials class, for which the constraints are ignored. @Entity( name = "admin.Credentials" ) @Table( name = "admin_credentials" , schema = "admin" ) public class AdminCredentials extends ModelBase { private static final long serialVersionUID = 1L; /** Credentials linked with an administrative account */ @OneToOne( optional = false ) @JoinColumn( name = "credentials_id" , referencedColumnName = "id" , nullable = false , updatable = false ) public Credentials credentials; /* Some more fields here */ } The code that attempts to delete the Credentials instances is: try { if ( account.validationKey != null ) { this.hTemplate.delete( account.validationKey ); } this.hTemplate.delete( account.languageSetting ); this.hTemplate.delete( account ); } catch ( DataIntegrityViolationException e ) { return false; } Where hTemplate is a HibernateTemplate instance provided by Spring, its flush mode having been set to EAGER. In the conditions shown above, the deletion will fail if there is an Account instance that refers to the Credentials instance being deleted, which is the expected behaviour. However, an AdminCredentials instance will be ignored, the deletion will succeed, leaving an invalid AdminCredentials instance behind (trying to refresh that instance causes an error because the Credentials instance no longer exists). I have tried moving the AdminCredentials table from the admin DB schema to the users DB schema. Strangely enough, a deletion-related error is then triggered, but not in the deletion code - it is triggered at the next query involving the table, seemingly ignoring the flush mode setting. I've been trying to understand this for hours and I must admit I'm just as clueless now as I was then.

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Turn class "Interfaceable"

- by scooterman

Hi folks, On my company system, we use a class to represent beans. It is just a holder of information using boost::variant and some serialization/deserialization stuff. It works well, but we have a problem: it is not over an interface, and since we use modularization through dlls, building an interface for it is getting very complicated, since it is used in almost every part of our app, and sadly interfaces (abstract classes ) on c++ have to be accessed through pointers, witch makes almost impossible to refactor the entire system. Our structure is: dll A: interface definition through abstract class dll B: interface implementation there is a painless way to achieve that (maybe using templates, I don't know) or I should forget about making this work and simply link everything with dll B? thanks Edit: Here is my example. this is on dll A BeanProtocol is a holder of N dataprotocol itens, wich are acessed by a index. class DataProtocol; class UTILS_EXPORT BeanProtocol { public: virtual DataProtocol& get(const unsigned int ) const { throw std::runtime_error("Not implemented"); } virtual void getFields(std::list<unsigned int>&) const { throw std::runtime_error("Not implemented"); } virtual DataProtocol& operator[](const unsigned int ) { throw std::runtime_error("Not implemented"); } virtual DataProtocol& operator[](const unsigned int ) const { throw std::runtime_error("Not implemented"); } virtual void fromString(const std::string&) { throw std::runtime_error("Not implemented"); } virtual std::string toString() const { throw std::runtime_error("Not implemented"); } virtual void fromBinary(const std::string&) { throw std::runtime_error("Not implemented"); } virtual std::string toBinary() const { throw std::runtime_error("Not implemented"); } virtual BeanProtocol& operator=(const BeanProtocol&) { throw std::runtime_error("Not implemented"); } virtual bool operator==(const BeanProtocol&) const { throw std::runtime_error("Not implemented"); } virtual bool operator!=(const BeanProtocol&) const { throw std::runtime_error("Not implemented"); } virtual bool operator==(const char*) const { throw std::runtime_error("Not implemented"); } virtual bool hasKey(unsigned int field) const { throw std::runtime_error("Not implemented"); } }; the other class (named GenericBean) implements it. This is the only way I've found to make this work, but now I want to turn it in a truly interface and remove the UTILS_EXPORT (which is an _declspec macro), and finally remove the forced linkage of B with A.

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OpenGL Polygon Stipple Not Working On Different Machine

- by FranticPedantic

I have a situation where I am trying to draw a semi-transparent rectangle over a background that is not using openGL and so I can not use blending. I decided to use polygon stippling for a 'screen door transparency' effect as recommended by some. It works fine on my machine and some others, but on some machines with slightly old Intel graphics cards it's failing to render the rectangle at all. If I turn off polygon stipple, it renders fine (but without the stipple). I have compared many of the state variables that I thought might affect it (see code) between machines and they are all the same, and I get no errors. static const GLubyte stipplePatternChkr[128]; //definition omitted for clarity //but works on my machine // stipple the box glPolygonMode(GL_FRONT_AND_BACK, GL_FILL); glColor4ubv(Color(COLORREF_PADGRAY)); glEnable(GL_POLYGON_STIPPLE); glPolygonStipple(stipplePatternChkr); CRect rcStipple(dim); rcStipple.DeflateRect(padding - 1, padding - 1); glBegin(GL_QUADS); glVertex2i(rcStipple.left, rcStipple.bottom); glVertex2i(rcStipple.right, rcStipple.bottom); glVertex2i(rcStipple.right, rcStipple.top); glVertex2i(rcStipple.left, rcStipple.top); glEnd(); glDisable(GL_POLYGON_STIPPLE); int err = glGetError(); if (err != GL_NO_ERROR) { TRACE("glError(%s: %s)\n", s, gluErrorString(err)); } float x; glGetFloatv(GL_UNPACK_ALIGNMENT, &x); TRACE("unpack alignment %f\n", x); glGetFloatv(GL_UNPACK_IMAGE_HEIGHT, &x); TRACE("unpack height %f\n", x); glGetFloatv(GL_UNPACK_LSB_FIRST, &x); TRACE("unpack lsb %f\n", x); glGetFloatv(GL_UNPACK_ROW_LENGTH, &x); TRACE("unpack length %f\n", x); glGetFloatv(GL_UNPACK_SKIP_PIXELS, &x); TRACE("upnack skip %f\n", x); glGetFloatv(GL_UNPACK_SWAP_BYTES, &x); TRACE("upnack swap %f\n", x);

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Undefined Behavior and Sequence Points Reloaded

- by Nawaz

Consider this topic a sequel of the following topic: Previous Installment Undefined Behavior and Sequence Points Let's revisit this funny and convoluted expression (the italicized phrases are taken from the above topic *smile* ): i += ++i; We say this invokes undefined-behavior. I presume that when say this, we implicitly assume that type of i is one of built-in types. So my question is: what if the type of i is a user-defined type? Say it's type is Index which is defined later in this post (see below). Would it still invoke undefined-behavior? If yes, why? Is it not equivalent to writing i.operator+=(i.operator ++()); or even syntactically simpler i.add(i.inc());? Or, do they too invoke undefined-behavior? If no, why not? After all, the object i gets modified twice between consecutive sequence points. Please recall the rule of thumb : an expression can modify an object's value only once between consecutive "sequence points. And if i += ++i is an expression, then it must invoke undefined-behavior. If so, then it's equivalents i.operator+=(i.operator ++()); and i.add(i.inc()); must also invoke undefined-behavior which seems to be untrue! (as far as I understand) Or, i += ++i is not an expression to begin with? If so, then what is it and what is the definition of expression? If it's an expression, and at the same time, it's behavior is also well-defined, then it implies that number of sequence points associated with an expression somehow depends on the type of operands involved in the expression. Am I correct (even partly)? By the way, how about this expression? a[++i] = i; //taken from the previous topic. but here type of `i` is Index. class Index { int state; public: Index(int s) : state(s) {} Index& operator++() { state++; return *this; } Index& operator+=(const Index & index) { state+= index.state; return *this; } operator int() { return state; } Index & add(const Index & index) { state += index.state; return *this; } Index & inc() { state++; return *this; } };

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C++ EZWindows Linker Errors when trying to run demos

- by Brent Nash

I'm attempting to download and use the EZWindows ( http://www.cs.virginia.edu/c++programdesign/software/ ) SPARC installation (the http://www.cs.virginia.edu/c++programdesign/software/EzWindows2a-SPARC.tar.gz file). When trying to build some of the examples that come with it, I'm getting some linker errors that I just can't figure out. Here's the result of the uname -a command on the machine I'm running on (on which I am NOT an administrator): SunOS AAA.BBB.edu 5.10 Generic_138888-07 sun4v sparc SUNW,T5240 And here is the result of the g++ -v command: gcc version 2.95.2 19991024 (release) If you untar/unzip the package, I'm trying to compile the example in samples/chap03/lawn by simply doing "gmake" in that directory, here's what I get. Here's the error I get: bash-3.00$ gtar xfz EzWindows2a-SPARC.tar.gz gtar: Removing leading `./' from member names bash-3.00$ cd chap03/lawn bash-3.00$ gmake clean ; gmake rm -f *.o *~ lawn make lawn g++ -I/X11.6/include -I../../EzWindows/include -c prog3-5.cpp prog3-5.cpp: In function `int ApiMain()': prog3-5.cpp:75: warning: initialization to `long int' from `const float' prog3-5.cpp:85: warning: initialization to `int' from `float' prog3-5.cpp:86: warning: initialization to `int' from `float' g++ -o lawn prog3-5.o -L/X11.6/lib -R/X11.6/lib -lX11 -lsocket -L../../EzWindows/lib -lezwin -lXpm ld: warning: symbol `clog' has differing types: (file /usr/usc/gnu/gcc/2.95.2/lib/gcc-lib/sparc-sun-solaris2.6/2.95.2/libstdc++.so type=OBJT; file /lib/libm.so type=FUNC); /usr/usc/gnu/gcc/2.95.2/lib/gcc-lib/sparc-sun-solaris2.6/2.95.2/libstdc++.so definition taken Undefined first referenced symbol in file __dl__Q2t12basic_string3ZcZt18string_char_traits1ZcZt24__default_alloc_template2b0i03RepPv ../../EzWindows/lib/libezwin.a(WindowManager.o) __eh_pc ../../EzWindows/lib/libezwin.a(WindowManager.o) clone__Q2t12basic_string3ZcZt18string_char_traits1ZcZt24__default_alloc_template2b0i03Rep ../../EzWindows/lib/libezwin.a(WindowManager.o) ld: fatal: Symbol referencing errors. No output written to lawn collect2: ld returned 1 exit status *** Error code 1 make: Fatal error: Command failed for target `lawn' Current working directory /export/samfs-bcf/rcf-11/bnash/sparc/chap03/lawn gmake: *** [default] Error 1 This particular run was built using g++ 2.95.2, but I've also tried with versions 3.3.2 and 4.2.1 with other equally strange errors. I'm pretty sure that EZWindows requires a 2.x version of gcc & g++. I've tried to make sure that my LD_LIBRARY_PATH and PATH are setup to include everything that's needed, but it seems that may be incorrect. I'm running out of ideas. Anyone have any other ones?

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How to best integrate generated code

- by Arne

I am evaluating the use of code generation for my flight simulation project. More specifically there is a requirement to allow "the average engineer" (no offense I am one myself) to define the differential equations that describe the dynamic system in a more natural syntax than C++ provides. The idea is to devise a abstract descriptor language that can be easily understood and edited to generate C++ code from. This descriptor is supplied by the modeling engineer and used by the ones implementing and maintaining the simulation evironment to generate code. I've got something like this in mind: model Aircraft has state x1, x2; state x3; input double : u; input bool : flag1, flag2; algebraic double : x1x2; model Engine : tw1, tw2; model Gear : gear; model ISA : isa; trim routine HorizontalFight; trim routine OnGround, General; constant double : c1, c2; constant int : ci1; begin differential equations x1' = x1 + 2.*x2; x2' = x2 + x1x2; begin algebraic equations x1x2 = x1*x2 + x1'; end model It is important to retain the flexibility of the C language thus the descriptor language is meant to only define certain parts of the definition and implementation of the model class. This way one enigneer provides the model in from of the descriptor language as examplified above and the maintenance enigneer will add all the code to read parameters from files, start/stop/pause the execution of the simulation and how a concrete object gets instatiated. My first though is to either generate two files from the descriptor file: one .h file containing declarations and one .cpp file containing the implementation of certain functions. These then need to be #included at appropriate places [File Aircarft.h] class Aircraft { public: void Aircraft(..); // hand-written constructor void ReadParameters(string &file_name); // hand-written private: /* more hand wirtten boiler-plate code */ /* generate declarations follow */ #include "Aircraft.generated.decl" }; [File Aircraft.cpp] Aircarft::Aircraft(..) { /* hand-written constructer implementation */ } /* more hand-written implementation code */ /* generated implementation code follows */ #include "Aircraft.generated.impl" Any thoughts or suggestions?

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Blob object not working properly even though the class is seralized

- by GustlyWind

I have class which is seralized and does convert a very large amount of data object to blob to save it to database.In the same class there is decode method to convert blob to the actual object.Following is the code for encode and decode of the object. private byte[] encode(ScheduledReport schedSTDReport) { byte[] bytes = null; try { ByteArrayOutputStream bos = new ByteArrayOutputStream(); ObjectOutputStream oos = new ObjectOutputStream(bos); oos.writeObject(schedSTDReport); oos.flush(); oos.close(); bos.close(); //byte [] data = bos.toByteArray(); //ByteArrayOutputStream baos = new ByteArrayOutputStream(); //GZIPOutputStream out = new GZIPOutputStream(baos); //XMLEncoder encoder = new XMLEncoder(out); //encoder.writeObject(schedSTDReport); //encoder.close(); bytes = bos.toByteArray(); //GZIPOutputStream out = new GZIPOutputStream(bos); //out.write(bytes); //bytes = bos.toByteArray(); } catch (Exception e) { _log.error("Exception caught while encoding/zipping Scheduled STDReport", e); } decode(bytes); return bytes; } /* * Decode the report definition blob back to the * ScheduledReport object. */ private ScheduledReport decode(byte[] bytes) { ByteArrayInputStream bais = new ByteArrayInputStream(bytes); ScheduledReport sSTDR = null; try { ObjectInputStream ois = new ObjectInputStream(bais); //GZIPInputStream in = new GZIPInputStream(bais); //XMLDecoder decoder = new XMLDecoder(in); sSTDR = (ScheduledReport)ois.readObject();//decoder.readObject(); //decoder.close(); } catch (Exception e) { _log.error("IOException caught while decoding/unzipping Scheduled STDReport", e); } return sSTDR; } The problem here is whenver I change something else in this class means any other method,a new class version is created and so the new version the class is unable to decode the originally encoded blob object. The object which I am passing for encode is also seralized object but this problem exists. Any ideas thanks

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Is this scenario in compliance with GPLv3?

- by Sean Kinsey

For arguments sake, say that we create a web application , that depends on a GPLv3 licensed component, lets say Ext JS. Based on Section 0 of the license, the common notion is that the entire web application (the client side javascript) falls under the definition of a covered work: A “covered work” means either the unmodified Program or a work based on the Program. and that it will therefor have to be distributed under the same license Ok, so here comes the fun part: This is a short 'program' that is based on Ext JS var myPanel = new Ext.Panel(); The question that arises is: Have I now violated the GPL by not including the source of Ext JS and its license? Ok, so lets take another example <!doctype html> <html> <head> <title>my title</title> <script type="text/javascript" src="http://extjs.cachefly.net/ext-3.2.1/ext-all.js"> </script> <link rel="stylesheet" type="text/css" href="http://extjs.cachefly.net/ext-3.2.1/resources/css/ext-all.css" /> <script type="text/javascript"> var myPanel = new Ext.Panel(); </script> </head> <body> </body> </html> Have I now violated the terms of the GPL? The code conveyed by me to you is in a non-functional state - it will have to be combined with the actual source of Ext JS, which you(your browser) will have to retrieve, from a source made public by someone else to be usable. Now, if the answer to the above is no, how does me conveying this code in visible form differ from the 'invisible' form conveyed by my web server? As a side note, a very similar thing is done in Linux with many projects that depends on less permissive licenses - the user has to retrieve these on its own and make these available for the primary lib/executable. How is this not the same if the user is informed on beforehand that he (the browser) will have to retrieve the needed resources from a different source? Just to make it clear, I'm pro FLOSS, and I have also published a number of projects licensed under more permissive licenses. The reason I'm asking this is that I still haven't found anyone offering a definitive answer to this.

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What is `objc_msgSend_fixup`, exactly?

- by Luis Antonio Botelho O. Leite

I'm messing around with the Objective-C runtime, trying to compile objective-c code without linking it against libobjc, and I'm having some segmentation fault problems with a program, so I generated an assembly file from it. I think it's not necessary to show the whole assembly file. At some point of my main function, I've got the following line (which, by the way, is the line after which I get the seg fault): callq *l_objc_msgSend_fixup_alloc and here is the definition for l_objc_msgSend_fixup_alloc: .hidden l_objc_msgSend_fixup_alloc # @"\01l_objc_msgSend_fixup_alloc" .type l_objc_msgSend_fixup_alloc,@object .section "__DATA, __objc_msgrefs, coalesced","aw",@progbits .weak l_objc_msgSend_fixup_alloc .align 16 l_objc_msgSend_fixup_alloc: .quad objc_msgSend_fixup .quad L_OBJC_METH_VAR_NAME_ .size l_objc_msgSend_fixup_alloc, 16 I've reimplemented objc_msgSend_fixup as a function (id objc_msgSend_fixup(id self, SEL op, ...)) which returns nil (just to see what happens), but this function isn't even being called (the program crashes before calling it). So, my question is, what is callq *l_objc_msgSend_fixup_alloc supposed to do and what is objc_msgSend_fixup (after l_objc_msgSend_fixup_alloc:) supposed to be (a function or an object)? Edit To better explain, I'm not linking my source file against the objc library. What I'm trying to do is implement some parts of the libray, just to see how it works. Here is an approach of what I've done: #include <stdio.h> #include <objc/runtime.h> @interface MyClass { } +(id) alloc; @end @implementation MyClass +(id) alloc { // alloc the object return nil; } @end id objc_msgSend_fixup(id self, SEL op, ...) { printf("Calling objc_msgSend_fixup()...\n"); // looks for the method implementation for SEL in self's vtable return nil; // Since this is just a test, this function doesn't need to do that } int main(int argc, char *argv[]) { MyClass *m; m = [MyClass alloc]; // At this point, according to the assembly code generated // objc_msgSend_fixup should be called. So, the program should, at least, print // "Calling objc_msgSend_fixup()..." on the screen, but it crashes before // objc_msgSend_fixup() is called... return 0; } If the runtime needs to access the object's vtable to find the correct method to call, what is the function which actually does this? I think it is objc_msgSend_fixup, in this case. So, when objc_msgSend_fixup is called, it receives an object as one of its parameters, and, if this object hasn't been initialized, the function fails. So, I've implemented my own version of objc_msgSend_fixup. According to the assembly source above, it should be called. It doesn't matter if the function is actually looking for the implementation of the selector passed as parameter. I just want objc_msgSend_lookup to be called. But, it's not being called, that is, the function that looks for the object's data is not even being called, instead of being called and cause a fault (because it returns a nil (which, by the way, doesn't matter)). The program seg fails before objc_msgSend_lookup is called...

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References between Spring beans when using a NameSpaceHandler

- by teabot

I'm trying to use a Spring context namespace to build some existing configuration objects in an application. I have defined a context and pretty much have if working satisfactorily - however, I'd like one bean defined by my namespace to implicitly reference another: Consider the class named 'Node': public Class Node { private String aField; private Node nextNode; public Node(String aField, Node nextNode) { ... } Now in my Spring context I have something like so: <myns:container> <myns:node aField="nodeOne"/> <myns:node aField="nodeTwo"/> </myns:container> Now I'd like nodeOne.getNode() == nodeTwo to be true. So that nodeOne.getNode() and nodeTwo refer to the same bean instance. These are pretty much the relevant parts I have in my AbstractBeanDefinitionParser: public AbstractBeanDefinition parseInternal(Element element, ParserContext parserContext) { ... BeanDefinitionBuilder containerFactory = BeanDefinitionBuilder.rootBeanDefinition(ContainerFactoryBean.class); List<BeanDefinition> containerNodes = Lists.newArrayList(); String previousNodeBeanName; // iterate backwards over the 'node' elements for (int i = nodeElements.size() - 1; i >= 0; --i) { BeanDefinitionBuilder node = BeanDefinitionBuilder.rootBeanDefinition(Node.class); node.setScope(BeanDefinition.SCOPE_SINGLETON); String nodeField = nodeElements.getAttribute("aField"); node.addConstructorArgValue(nodeField); if (previousNodeBeanName != null) { node.addConstructorArgValue(new RuntimeBeanReference(previousNodeBeanName)); } else { node.addConstructorArgValue(null); } BeanDefinition nodeDefinition = node.getBeanDefinition(); previousNodeBeanName = "inner-node-" + nodeField; parserContext.getRegistry().registerBeanDefinition(previousNodeBeanName, nodeDefinition); containerNodes.add(node); } containerFactory.addPropertyValue("nodes", containerNodes); } When the application context is created my Node instances are created and recognized as singletons. Furthermore, the nextNode property is populated with a Node instance with the previous nodes configuration - however, it isn't the same instance. If I output a log message in Node's constructor I see two instances created for each node bean definition. I can think of a few workarounds myself but I'm keen to use the existing model. So can anyone tell me how I can pass these runtime bean references so that I get the correct singleton behaviour for my Node instances?

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Mailer issue, PHP values do not change

- by Roland

I have a script that runs once every month and send out stats to clients, now the stats are displayed in normal text and in the shape of a Pie Graph, now if I run the script mannually from the command line all info on the graphs are correct, but when the cron job executes the script the values for the first client are displaying on the graphs of all clients. but the text is correct. I'm using domDocument to build the HTML and PHPMailer to send out the email with the Graphs embedded into the mail also use pChart to generate the Graph My code that generates the PIE graph is below include_once "pChart.1.26e/pChart/pData.class"; include_once "pChart.1.26e/pChart/pChart.class"; // Dataset definition unset($DataSet); $DataSet = new pData; $DataSet->AddPoint(array($data['total_clicks'],$remaining),"Serie1"); if($remaining < 0){ $DataSet->AddPoint(array("Clicks delivered todate","Clicks remaining = 0"),"Serie2"); }else{ $DataSet->AddPoint(array("Clicks delivered todate","Clicks remaining"),"Serie2"); } $DataSet->AddAllSeries(); $DataSet->SetAbsciseLabelSerie("Serie2"); // Initialise the graph $pie = new pChart(492,292); $pie->drawBackground(255,255,254); $pie->LineWidth = 1.1; $pie->Values = 2; // $pie->drawRoundedRectangle(5,5,375,195,5,230,230,230); //$pie->drawRectangle(0,0,480,288,169,169,169); $pie->drawRectangle(5,5,487,287,169,169,169); $pie->loadColorPalette('pChart.1.26e/color/tones-3.txt',','); // Draw the pie chart $pie->setFontProperties("pChart.1.26e/Fonts/calibrib.ttf",18); $pie->drawTitle(140,33,"Campaign Overview",0,0,0); $pie->setFontProperties("pChart.1.26e/Fonts/calibrib.ttf",11); $pie->drawTitle(343,125,"Total clicks : ".$total_clicks,0,0,0); $pie->setFontProperties("pChart.1.26e/Fonts/calibri.ttf",10); if($remaining < 0){ $pie->setFontProperties("pChart.1.26e/Fonts/calibrib.ttf",10); $pie->drawTitle(260,250,"Campaign over-delivered by ".substr($remaining,1)." clicks",205,53,53); $pie->setFontProperties("pChart.1.26e/Fonts/calibri.ttf",10); } $pie->drawPieLegend(328,140,$DataSet->GetData(),$DataSet->GetDataDescription(),255,255,255); $pie->drawPieGraph($DataSet->GetData(),$DataSet->GetDataDescription(),170,150,130,PIE_VALUE,FALSE,50,30,0); $pie->Render("generated/3dpie.png"); unset($pie); unset($DataSet); $mail->AddEmbeddedImage("/var/www/html/stats/generated/3dpie.png","5"); I just can't understand why this only happens when the cronjob runs?

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CoGetClassObject gives many First-chance exceptions in ATL project. Should I worry?

- by Andrew

Hello, I have written a COM object that in turn uses a thrid party ActiveX control. In my FinalConstruct() for my COM object, I instantiate the ActiveX control with the follow code: HRESULT hRes; LPCLASSFACTORY2 pClassFactory; hRes = CoInitializeEx(NULL,COINIT_APARTMENTTHREADED); bool bTest = SUCCEEDED(hRes); if (!bTest) return E_FAIL; if (SUCCEEDED(CoGetClassObject(__uuidof(SerialPortSniffer), CLSCTX_INPROC_SERVER, NULL, IID_IClassFactory2, (LPVOID *)(&pClassFactory)))) { ... more set up code When I step over the line if (SUCCEEDED(CoGetClassObject(__uuidof(SerialPortSniffer), ..., I get 20+ lines in the Output window stating: First-chance exception at 0x0523f82e in SillyComDriver.exe: 0xC0000005: Access violation writing location 0x00000000. I also get the lines: First-chance exception at 0x051e3f3d in SillyComDriver.exe: 0xC0000096: Privileged instruction. First-chance exception at 0x100ab9e6 in SillyComDriver.exe: 0xC000001D: Illegal Instruction. Notice these are first-chance exceptions. The program runs as expected I can access the third party methods/properties. Still, I'm left wondering why they are occurring. Perhaps my way of instantiating the ActiveX control (for which I want use of it's methods/properties and not it's GUI stuff) is incorrect? Besides the code I'm showing, I also put the line import "spsax.dll" no_namespace in the stdafx.h That's all the code necessary for my simple demo project. I noticed this problem because I had (inadvertently) set the "break on exceptions" options in my "real" project and it was breaking on this line. Once I removed it, it also works. If you're read this far thank you, and perhaps I can ask one other minor question. In my demo project, if I right click on SerialPortSniffer and "go to definition", it takes me to the file C:....\AppData\Local\Temp\spsax.tlh. Can someone explain that? Finally, in my "real" project, right clicking on SerialPortSniffer and going to difinition leads to "The symbol 'SerialPortSniffer' is not defined". It doesn't seem to affect the program though. Is there some setting I've messed up? By the way, all my code is written w/ VS2008. Thanks, Dave

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conflicting declaration when filling a static std::map class member variable

- by Max

I have a class with a static std::map member variable that maps chars to a custom type Terrain. I'm attempting to fill this map in the class's implementation file, but I get several errors. Here's my header file: #ifndef LEVEL_HPP #define LEVEL_HPP #include <bitset> #include <list> #include <map> #include <string> #include <vector> #include "libtcod.hpp" namespace yarl { namespace level { class Terrain { // Member Variables private: std::bitset<5> flags; // Member Functions public: explicit Terrain(const std::string& flg) : flags(flg) {} (...) }; class Level { private: static std::map<char, Terrain> terrainTypes; (...) }; } } #endif and here's my implementation file: #include <bitset> #include <list> #include <map> #include <string> #include <vector> #include "Level.hpp" #include "libtcod.hpp" using namespace std; namespace yarl { namespace level { /* fill Level::terrainTypes */ map<char,Terrain> Level::terrainTypes['.'] = Terrain("00001"); // clear map<char,Terrain> Level::terrainTypes[','] = Terrain("00001"); // clear map<char,Terrain> Level::terrainTypes['\''] = Terrain("00001"); // clear map<char,Terrain> Level::terrainTypes['`'] = Terrain("00001"); // clear map<char,Terrain> Level::terrainTypes[178] = Terrain("11111"); // wall (...) } } I'm using g++, and the errors I get are src/Level.cpp:15: error: conflicting declaration ‘std::map, std::allocator yarl::level::Level::terrainTypes [46]’ src/Level.hpp:104: error: ‘yarl::level::Level::terrainTypes’ has a previous declaration as ‘std::map, std::allocator yarl::level::Level::terrainTypes’ src/Level.cpp:15: error: declaration of ‘std::map, std::allocator yarl::level::Level::terrainTypes’ outside of class is not definition src/Level.cpp:15: error: conversion from ‘yarl::level::Terrain’ to non-scalar type ‘std::map, std::allocator ’ requested src/Level.cpp:15: error: ‘yarl::level::Level::terrainTypes’ cannot be initialized by a non-constant expression when being declared I get a set of these for each map assignment line in the implementation file. Anyone see what I'm doing wrong? Thanks for your help.

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should I ever put a major version number into a C#/Java namespace?

- by Andrew Patterson

I am designing a set of 'service' layer objects (data objects and interface definitions) for a WCF web service (that will be consumed by third party clients i.e. not in-house, so outside my direct control). I know that I am not going to get the interface definition exactly right - and am wanting to prepare for the time when I know that I will have to introduce a breaking set of new data objects. However, the reality of the world I am in is that I will also need to run my first version simultaneously for quite a while. The first version of my service will have URL of http://host/app/v1service.svc and when the times comes by new version will live at http://host/app/v2service.svc However, when it comes to the data objects and interfaces, I am toying with putting the 'major' version of the interface number into the actual namespace of the classes. namespace Company.Product.V1 { [DataContract(Namespace = "company-product-v1")] public class Widget { [DataMember] string widgetName; } public interface IFunction { Widget GetWidgetData(int code); } } When the time comes for a fundamental change to the service, I will introduce some classes like namespace Company.Product.V2 { [DataContract(Namespace = "company-product-v2")] public class Widget { [DataMember] int widgetCode; [DataMember] int widgetExpiry; } public interface IFunction { Widget GetWidgetData(int code); } } The advantages as I see it are that I will be able to have a single set of code serving both interface versions, sharing functionality where possible. This is because I will be able to reference both interface versions as a distinct set of C# objects. Similarly, clients may use both interface versions simultaneously, perhaps using V1.Widget in some legacy code whilst new bits move on to V2.Widget. Can anyone tell why this is a stupid idea? I have a nagging feeling that this is a bit smelly.. notes: I am obviously not proposing every single new version of the service would be in a new namespace. Presumably I will do as many non-breaking interface changes as possible, but I know that I will hit a point where all the data modelling will probably need a significant rewrite. I understand assembly versioning etc but I think this question is tangential to that type of versioning. But I could be wrong.

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