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• Compiler is able to find function without matching .h file is updated?

  - by Maxim Veksler

  Hello Friends, I'm writing a C University project and stumbled upon a compiler behavior which I don't understand. In this file http://code.google.com/p/openu-bsc-maximveksler/source/browse/trunk/20465/semester/tasks/maman14/alpha/maman14/assembler/phaseOne.c?r=112 I've added a call to function named freeAsmInstruction(). This function is defined in file named lineParser.c, yet I haven't updated the matching lineParser.h header file to include this function declaration. Why does this code compile? I would expect that gcc would fail to compile phaseOne.c until the correct lineParser.h is updated with the declaration of freeAsmInstruction(). I would appreciate an explanation. Thank you, Maxim

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• Java Compiler: Optimization of "cascaded" ifs and best practices?

  - by jens

  Hello, does the Java Compiler optimize a statement like this if (a == true) { if (b == true) { if (c == true) { if(d == true) { //code to process stands here } } } } to if (a == true && b==true && c==true && d == true) So thats my first question: Do both take exactly the same "CPU Cycles" or is the first variant "slowlier". My Second questin is, is the first variant with the cascaded if considered bad programming style as it is so verbose? (I like the first variant as I can better logically group my expressions and better comment them (my if statements are more complex than in the example), but maybe thats bad proramming style?) and even slowlier, thats why I am asking... Thanks Jens

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• Why doesn't Inno Setup compiler set the version info correctly from hudson?

  - by Tim

  If I run Inno Setup compiler from a command line/batch file it creates an exe with the version information in the file name. However, when I run from hudson (same command line) I don't get the version information. Perhaps I am missing something. Is this a known issue? This is the way I am doing it in the iss script file. #define FileVerStr GetFileVersion(SrcApp) EDIT: The env vars are all set for all users - not just my login - so the service has access to everything that the command line build does. EDIT: See my answer for a resolution of this.

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• How do I get the XAML compiler to use textual content property on custom classes?

  - by Duncan

  Given a simple C# class definition like: [System.Windows.Markup.ContentProperty("PropertyOne")] public class SimpleBase { public string PropertyOne { get; set; } public string PropertyTwo { get; set; } } why is it not possible to omit the sys:string tags around the word Test in the xaml below. <custom:SimpleBase x:Class="TestType" xmlns:custom="clr-namespace:ConsoleApplication1;assembly=" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:sys="clr-namespace:System;assembly=mscorlib"> <sys:String>Test</sys:String> </custom:SimpleBase> Somehow the compiler correctly converts text to string for the type String, why doesn't it work for my custom type? The context can be found on my blog: http://www.deconflations.com/?tag=xaml

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• Any difference in compiler behavior for each of these snippets?

  - by HotHead

  Please consider following code: 1. uint16 a = 0x0001; if(a < 0x0002) { // do something } 2. uint16 a = 0x0001; if(a < uint16(0x0002)) { // do something } 3. uint16 a = 0x0001; if(a < static_cast<uint16>(0x0002)) { // do something } 4. uint16 a = 0x0001; uint16 b = 0x0002; if(a < b) { // do something } What compiler does in backgorund and what is the best (and correct) way to do above testing? p.s. sorry, but I couldn't find the better title :) EDIT: values 0x0001 and 0x0002 are only example. There coudl be any 2 byte value instead. Thank you in advance!

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• Why is passing a string literal into a char* arguament only sometimes a compiler error?

  - by Brian Postow

  I'm working in a C, and C++ program. We used to be compiling without the make-strings-writable option. But that was getting a bunch of warnings, so I turned it off. Then I got a whole bunch of errors of the form "Cannot convert const char* to char* in argmuent 3 of function foo". So, I went through and made a whole lot of changes to fix those. However, today, the program CRASHED because the literal "" was getting passed into a function that was expecting a char*, and was setting the 0th character to 0. It wasn't doing anything bad, just trying to edit a constant, and crashing. My question is, why wasn't that a compiler error? In case it matters, this was on a mac compiled with gcc-4.0.

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• C variable decleration on gcc compiler - compile time error.

  - by liv2hak

  Assume the following C variable decleration int *A[10] , B[10][10]; Of the following expressions A[2] A[2][3] B[1] B[2][3] which will not give compile time errors if used as left hand sides of assignment statements in a C program. A) 1,2 and 4 only B) 2,3, and 4 only C) 2 and 4 only D) 4 only I have tried this on a gcc compiler.I assigned the value '0' to all the above variables.Only the third one showed an error.I can't really understand the reason.Can someone please expalin why that is.? Thanks

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• Is it possible to avoid C++ compiler error (C2757) where 2 different header files contain same symbol for namespace & class?

  - by dharmendra

  Hi, I am facing a problem when implementing some new code to an existing library. This library already references a class with a name say 'foo'. The same name is used as a namespace in the other header file which has to be included to implement the new functionality. Since both the header files are a part of legacy code libraries I cannot amend them. So here I am looking for any way so as to avoid the Compiler Error (C2757: a symbol with this name already exists and therefore this name cannot be used as a namespace name). I am not sure whether it is possible or not. Hence, Any help shall be appreciated. Thanks For clarity here is the sample code illustration for the issue: HeaderA.h class foo {} HeaderB.h namespace foo { class ABC{} } HeaderC.h #include <HeaderA.h> #include <HeaderB.h> using namespace foo; class Toimplement{ ABC a; //Throws Error C2757 }

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• Doesnt the Visual Studio 2008 compiler autocast to double with sqrt in C++?

  - by Chris_45

  Shouldn't the compiler automatically cast to a double in this case at least according to Walter Savitch: #include <iostream> #include <cmath> using namespace std; int main(){ int k; for(k = 1; k <= 10; k++) cout << "The square root of i is: " << sqrt(k) << endl; return 0; }//error C2668: 'sqrt' : ambiguous call to overloaded function //Visual Studio 2008 on Win Vista

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• Scala loop returns as Unit and compiler points to "for" syntax?

  - by DeLongey

  Seems like Unit is the theme of my troubles today. I'm porting a JSON deserializer that uses Gson and when it comes to this for loop: def deserialize(json:JsonElement, typeOfT:Type, context:JsonDeserializationContext) = { var eventData = new EventData(null, null) var jsonObject = json.getAsJsonObject for(entry <- jsonObject.entrySet()) { var key = entry.getKey() var element = entry.getValue() element if("previous_attributes".equals(key)) { var previousAttributes = new scala.collection.mutable.HashMap[String, Object]() populateMapFromJSONObject(previousAttributes, element.getAsJsonObject()) eventData.setPreviousAttributes(previousAttributes) eventData } else if ("object".equals(key)) { val `type` = element.getAsJsonObject().get("object").getAsString() var cl = objectMap.get(`type`).asInstanceOf[StripeObject] var `object` = abstractObject.retrieve(cl, key) eventData.setObject(`object`) eventData } } } The compiler spits out the error type mismatch; found : Unit required: com.stripe.EventData and it points to this line here: for(entry <- jsonObject.entrySet()) Questions Confirm that it is indeed the Gson method entrySet() appearing as unit? If not, what part of the code is creating the issue? I've set return types/values for eventData class methods Is there a workaround for the Gson Unit issue? Thanks!

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• Static constructor can run after the non-static constructor. Is this a compiler bug?

  - by Joe H

  The output from the following program is: Non-Static Static Non-Static Is this a compiler bug? I expected: Static Non-Static Non-Static because I thought the static constructor was ALWAYS called before the non-static constructor. I tested this with Visual Studio 2010 using both .net 3.5 and .net 4.0. using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace StaticConstructorBug { class Program { static void Main(string[] args) { var mc = new MyClass(); Console.ReadKey(); } } public class MyClass { public MyClass() { Console.WriteLine("Non-static"); } static MyClass() { Console.WriteLine("Static"); } public static MyClass aVar = new MyClass(); } }

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• Why isn't the compiler smarter in this const function overloading problem?

  - by Frank

  The following code does not compile: #include <iostream> class Foo { std::string s; public: const std::string& GetString() const { return s; } std::string* GetString() { return &s; } }; int main(int argc, char** argv){ Foo foo; const std::string& s = foo.GetString(); // error return 0; } I get the following error: const1.cc:11: error: invalid initialization of reference of type 'const std::string&' from expression of type 'std::string* It does make some sense because foo is not of type const Foo, but just Foo, so the compiler wants to use the non-const function. But still, why can't it recognize that I want to call the const GetString function, by looking at the (type of) variable I assign it to? I found this kind of surprising.

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• Shall I optimize or let compiler to do that?

  - by Knowing me knowing you

  What is the preferred method of writing loops according to efficiency: Way a) /*here I'm hoping that compiler will optimize this code and won't be calling size every time it iterates through this loop*/ for (unsigned i = firstString.size(); i < anotherString.size(), ++i) { //do something } or maybe should I do it this way: Way b) unsigned first = firstString.size(); unsigned second = anotherString.size(); and now I can write: for (unsigned i = first; i < second, ++i) { //do something } the second way seems to me like worse option for two reasons: scope polluting and verbosity but it has the advantage of being sure that size() will be invoked once for each object. Looking forward to your answers.

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• Why does the compiler give an ambiguous invocation error when passing inherited types?

  - by Matt Mitchell

  What is happening in the C# compiler to cause the following ambiguous invocation compilation error? The same issue applies to extension methods, or when TestClass is generic and using instance rather than static methods. class Type1 { } class Type2 : Type1 {} class TestClass { public static void Do<T>(T something, object o) where T : Type1 {} public static void Do(Type1 something, string o) {} } void Main() { var firstInstance = new Type1(); TestClass.Do(firstInstance, new object()); // Calls Do(Type1, obj) TestClass.Do(firstInstance, "Test"); // Calls Do<T>(T, string) var secondInstance = new Type2(); TestClass.Do(secondInstance, new object()); // Calls Do(Type1, obj) TestClass.Do(secondInstance, "Test"); // "The call is ambiguous" compile error }

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• Auto not being recognised by the compiler, what would be the best replacement?

  - by user1719605

  So I have wrote a program that uses auto however the compiler doesn't seem to recognize it, probably it is an earlier compiler. I was wondering for my code, with are suitable variables to fix my code so that I do not need to use the auto keyword? I'm thinking a pointer to a string? or a string iterator, though I am not sure. #include <cstdlib> #include <string> #include <iostream> #include <unistd.h> #include <algorithm> using namespace std; int main(int argc, char* argv[]) { enum MODE { WHOLE, PREFIX, SUFFIX, ANYWHERE, EMBEDDED } mode = WHOLE; bool reverse_match = false; int c; while ((c = getopt(argc, argv, ":wpsaev")) != -1) { switch (c) { case 'w': // pattern matches whole word mode = WHOLE; break; case 'p': // pattern matches prefix mode = PREFIX; break; case 'a': // pattern matches anywhere mode = ANYWHERE; break; case 's': // pattern matches suffix mode = SUFFIX; break; case 'e': // pattern matches anywhere mode = EMBEDDED; break; case 'v': // reverse sense of match reverse_match = true; break; } } argc -= optind; argv += optind; string pattern = argv[0]; string word; int matches = 0; while (cin >> word) { switch (mode) { case WHOLE: if (reverse_match) { if (pattern != word) { matches += 1; cout << word << endl; } } else if (pattern == word) { matches += 1; cout << word << endl; } break; case PREFIX: if (pattern.size() <= word.size()) { auto res = mismatch(pattern.begin(), pattern.end(), word.begin()); if (reverse_match) { if (res.first != word.end()) { matches += 1; cout << word << endl; } } else if (res.first == word.end()) { matches += 1; cout << word << endl; } } break; case ANYWHERE: if (reverse_match) { if (!word.find(pattern) != string::npos) { matches += 1; cout << word << endl; } } else if (word.find(pattern) != string::npos) { matches += 1; cout << word << endl; } break; case SUFFIX: if (pattern.size() <= word.size()) { auto res = mismatch(pattern.rbegin(), pattern.rend(), word.rbegin()); if (reverse_match) { if (res.first != word.rend()) { matches = +1; cout << word << endl; } } else if (res.first == word.rend()) { matches = +1; cout << word << endl; } } break; case EMBEDDED: if (reverse_match) { if (!pattern.find(word) != string::npos) { matches += 1; cout << word << endl;} } else if (pattern.find(word) != string::npos) { matches += 1; cout << word << endl; } break; } } return (matches == 0) ? 1 : 0; } Thanks in advance!

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• Who could ask for more with LESS CSS? (Part 3 of 3&ndash;Clrizr)

  - by ToString(theory);

  Welcome back!  In the first two posts in this series, I covered some of the awesome features in CSS precompilers such as SASS and LESS, as well as how to get an initial project setup up and running in ASP.Net MVC 4. In this post, I will cover an actual advanced example of using LESS in a project, and show some of the great productivity features we gain from its usage. Introduction In the first post, I mentioned two subjects that I will be using in this example – constants, and color functions.  I’ve always enjoyed using online color scheme utilities such as Adobe Kuler or Color Scheme Designer to come up with a scheme based off of one primary color.  Using these tools, and requesting a complementary scheme you can get a couple of shades of your primary color, and a couple of shades of a complementary/accent color to display. Because there is no way in regular css to do color operations or store variables, there was no way to accomplish something like defining a primary color, and have a site theme cascade off of that.  However with tools such as LESS, that impossibility becomes a reality!  So, if you haven’t guessed it by now, this post is on the creation of a plugin/module/less file to drop into your project, plugin one color, and have your primary theme cascade from it.  I only went through the trouble of creating a module for getting Complementary colors.  However, it wouldn’t be too much trouble to go through other options such as Triad or Monochromatic to get a module that you could use off of that. Step 1 – Analysis I decided to mimic Adobe Kuler’s Complementary theme algorithm as I liked its simplicity and aesthetics.  Color Scheme Designer is great, but I do believe it can give you too many color options, which can lead to chaos and overload.  The first thing I had to check was if the complementary values for the color schemes were actually hues rotated by 180 degrees at all times – they aren’t.  Apparently Adobe applies some variance to the complementary colors to get colors that are actually more aesthetically appealing to users.  So, I opened up Excel and began to plot complementary hues based on rotation in increments of 10: Long story short, I completed the same calculations for Hue, Saturation, and Lightness.  For Hue, I only had to record the Complementary hue values, however for saturation and lightness, I had to record the values for ALL of the shades.  Since the functions were too complicated to put into LESS since they aren’t constant/linear, but rather interval functions, I instead opted to extrapolate the HSL values using the trendline function for each major interval, onto intervals of spacing 1. For example, using the hue extraction, I got the following values: Interval Function 0-60 60-140 140-270 270-360 Saturation and Lightness were much worse, but in the end, I finally had functions for all of the intervals, and then went the route of just grabbing each shades value in intervals of 1.  Step 2 – Mapping I declared variable names for each of these sections as something that shouldn’t ever conflict with a variable someone would define in their own file.  After I had each of the values, I extracted the values and put them into files of their own for hue variables, saturation variables, and lightness variables…  Example: /*HUE CONVERSIONS*/@clrizr-hue-source-0deg: 133.43;@clrizr-hue-source-1deg: 135.601;@clrizr-hue-source-2deg: 137.772;@clrizr-hue-source-3deg: 139.943;@clrizr-hue-source-4deg: 142.114;.../*SATURATION CONVERSIONS*/@clrizr-saturation-s2SV0px: 0;@clrizr-saturation-s2SV1px: 0;@clrizr-saturation-s2SV2px: 0;@clrizr-saturation-s2SV3px: 0;@clrizr-saturation-s2SV4px: 0;.../*LIGHTNESS CONVERSIONS*/@clrizr-lightness-s2LV0px: 30;@clrizr-lightness-s2LV1px: 31;@clrizr-lightness-s2LV2px: 32;@clrizr-lightness-s2LV3px: 33;@clrizr-lightness-s2LV4px: 34;...   In the end, I have 973 lines of mapping/conversion from source HSL to shade HSL for two extra primary shades, and two complementary shades. The last bit of the work was the file to compose each of the shades from these mappings. Step 3 – Clrizr Mapper The final step was the hardest to overcome as I was still trying to understand LESS to its fullest extent.  Imports As mentioned previously, I had separated the HSL mappings into different files, so the first necessary step is to import those for use into the Clrizr plugin: @import url("hue.less");@import url("saturation.less");@import url("lightness.less"); Extract Component Values For Each Shade Next, I extracted the necessary information for each shade HSL before shade composition: @clrizr-input-saturation: 1px+floor(saturation(@clrizr-input))-1;@clrizr-input-lightness: 1px+floor(lightness(@clrizr-input))-1; @clrizr-complementary-hue: formatstring("clrizr-hue-source-{0}", ceil(hue(@clrizr-input))); @clrizr-primary-2-saturation: formatstring("clrizr-saturation-s2SV{0}",@clrizr-input-saturation);@clrizr-primary-1-saturation: formatstring("clrizr-saturation-s1SV{0}",@clrizr-input-saturation);@clrizr-complementary-1-saturation: formatstring("clrizr-saturation-c1SV{0}",@clrizr-input-saturation); @clrizr-primary-2-lightness: formatstring("clrizr-lightness-s2LV{0}",@clrizr-input-lightness);@clrizr-primary-1-lightness: formatstring("clrizr-lightness-s1LV{0}",@clrizr-input-lightness);@clrizr-complementary-1-lightness: formatstring("clrizr-lightness-c1LV{0}",@clrizr-input-lightness); Here, you can see a couple of odd things…  On the first line, I am using operations to add units to the saturation and lightness.  This is due to some limitations in the operations that would give me saturation or lightness in %, which can’t be in a variable name.  So, I use first add 1px to it, which casts the result of the following functions as px instead of %, and then at the end, I remove that pixel.  You can also see here the formatstring method which is exactly what it sounds like – something like String.Format(string str, params object[] obj). Get Primary & Complementary Shades Now that I have components for each of the different shades, I can now compose them into each of their pieces.  For this, I use the @@ operator which will look for a variable with the name specified in a string, and then call that variable: @clrizr-primary-2: hsl(hue(@clrizr-input), @@clrizr-primary-2-saturation, @@clrizr-primary-2-lightness);@clrizr-primary-1: hsl(hue(@clrizr-input), @@clrizr-primary-1-saturation, @@clrizr-primary-1-lightness);@clrizr-primary: @clrizr-input;@clrizr-complementary-1: hsl(@@clrizr-complementary-hue, @@clrizr-complementary-1-saturation, @@clrizr-complementary-1-lightness);@clrizr-complementary-2: hsl(@@clrizr-complementary-hue, saturation(@clrizr-input), lightness(@clrizr-input)); That’s is it, for the most part.  These variables now hold the theme for the one input color – @clrizr-input.  However, I have one last addition… Perceptive Luminance Well, after I got the colors, I decided I wanted to also get the best font color that would go on top of it.  Black or white depending on light or dark color.  Now I couldn’t just go with checking the lightness, as that is half the story.  You see, the human eye doesn’t see ALL colors equally well but rather has more cells for interpreting green light compared to blue or red.  So, using the ratio, we can calculate the perceptive luminance of each of the shades, and get the font color that best matches it! @clrizr-perceptive-luminance-ps2: round(1 - ( (0.299 * red(@clrizr-primary-2) ) + ( 0.587 * green(@clrizr-primary-2) ) + (0.114 * blue(@clrizr-primary-2)))/255)*255;@clrizr-perceptive-luminance-ps1: round(1 - ( (0.299 * red(@clrizr-primary-1) ) + ( 0.587 * green(@clrizr-primary-1) ) + (0.114 * blue(@clrizr-primary-1)))/255)*255;@clrizr-perceptive-luminance-ps: round(1 - ( (0.299 * red(@clrizr-primary) ) + ( 0.587 * green(@clrizr-primary) ) + (0.114 * blue(@clrizr-primary)))/255)*255;@clrizr-perceptive-luminance-pc1: round(1 - ( (0.299 * red(@clrizr-complementary-1)) + ( 0.587 * green(@clrizr-complementary-1)) + (0.114 * blue(@clrizr-complementary-1)))/255)*255;@clrizr-perceptive-luminance-pc2: round(1 - ( (0.299 * red(@clrizr-complementary-2)) + ( 0.587 * green(@clrizr-complementary-2)) + (0.114 * blue(@clrizr-complementary-2)))/255)*255; @clrizr-col-font-on-primary-2: rgb(@clrizr-perceptive-luminance-ps2, @clrizr-perceptive-luminance-ps2, @clrizr-perceptive-luminance-ps2);@clrizr-col-font-on-primary-1: rgb(@clrizr-perceptive-luminance-ps1, @clrizr-perceptive-luminance-ps1, @clrizr-perceptive-luminance-ps1);@clrizr-col-font-on-primary: rgb(@clrizr-perceptive-luminance-ps, @clrizr-perceptive-luminance-ps, @clrizr-perceptive-luminance-ps);@clrizr-col-font-on-complementary-1: rgb(@clrizr-perceptive-luminance-pc1, @clrizr-perceptive-luminance-pc1, @clrizr-perceptive-luminance-pc1);@clrizr-col-font-on-complementary-2: rgb(@clrizr-perceptive-luminance-pc2, @clrizr-perceptive-luminance-pc2, @clrizr-perceptive-luminance-pc2); Conclusion That’s it!  I have posted a project on clrizr.codePlex.com for this, and included a testing page for you to test out how it works.  Feel free to use it in your own project, and if you have any questions, comments or suggestions, please feel free to leave them here as a comment, or on the contact page!

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• Can I copy a cross compiler tool chain between systems (I did before)?

  - by Jamie

  I tested fairly extensively with Ubuntu 10.04 Beta 2 Server in a VM, and was able to simply copy (read tar x) a cross compiled tool chain from an Ubuntu 8.10 VM. I created the tar myself, which is essentially a lot of stuff in \usr\local. Now that I've got a bare metal installation of Ubuntu 10.04 proper, the copy isn't working. In particularly, I'm getting the error: $ arm-linux-gcc -bash: /usr/local/bin/arm-linux-gcc: No such file or directory I've got the systems side by side in SSH windows ... any suggestions?

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• Why can't the compiler/JVM just make autoboxing "just work"?

  - by Pyrolistical

  Autoboxing is rather scary. While I fully understand the difference between == and .equals I can't but help have the follow bug the hell out of me: final List<Integer> foo = Arrays.asList(1, 1000); final List<Integer> bar = Arrays.asList(1, 1000); System.out.println(foo.get(0) == bar.get(0)); System.out.println(foo.get(1) == bar.get(1)); That prints true false Why did they do it this way? It something to do with cached Integers, but if that is the case why don't they just cache all Integers used by the program? Or why doesn't the JVM always auto unbox to primitive? Printing false false or true true would have been way better. EDIT I disagree about breakage of old code. By having foo.get(0) == bar.get(0) return true you already broke the code. Can't this be solved at the compiler level by replacing Integer with int in byte code (as long as it is never assigned null)

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• Why compiler go to suspend mode when want to open database?

  - by rima

  Dear friend I try to connect to database with a less line for my connection string... I find out s.th in oracle website but i dont know Why when the compiler arrive to the line of open database do nothing????!it go back to GUI,but it like hanging...please help me to solve it. p.s.Its funny the program didnt get me any exception also! these service is active in my computer: > Oracle ORCL VSS Writer Service Start > OracleDBConsolrorcl > OracleJobSchedulerORCL Start > OracleOraDB11g+home1TNSListener Start > oracleServiceORCL Start try { /** * ORCL = (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = rima-PC)(PORT = 1521)) (CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = orcl) ) )*/ string oradb = "Data Source=(DESCRIPTION=" + "(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=rima-PC)(PORT=1521)))" + "(CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=orcl)));" + "User Id=bird_artus;Password=123456;"; //string oradb = "Data Source=OraDb;User Id=scott;Password=tiger;"; string oradb1 = "Data Source=ORCL;User Id=scott;Password=tiger;"; // C# OracleConnection con = new OracleConnection(); con.ConnectionString = oradb1; String command = "select dname from dept where deptno = 10"; MessageBox.Show(command); OracleDataAdapter oda = new OracleDataAdapter(); oda.SelectCommand = new OracleCommand(); oda.SelectCommand.Connection = con; oda.SelectCommand.CommandText = command; con.Open(); oda.SelectCommand.ExecuteNonQuery(); DataSet ds = new DataSet(); oda.Fill(ds); Console.WriteLine(ds.GetXml()); dataGridView1.DataSource = ds; con.Close(); } catch (Exception ex) { MessageBox.Show(ex.Message.ToString()+Environment.NewLine+ ex.StackTrace.ToString()); }

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• Declaring a string array in class header file - compiler thinks string is variable name?

  - by Dave

  Hey everybody, I need a bit of a hand with declaring a string array in my class header file in C++. atm it looks like this: //Maze.h #include <string> class Maze { GLfloat mazeSize, mazeX, mazeY, mazeZ; string* mazeLayout; public: Maze ( ); void render(); }; and the constructor looks like this: //Maze.cpp #include <GL/gl.h> #include "Maze.h" #include <iostream> #include <fstream> Maze::Maze( ) { cin >> mazeSize; mazeLayout = new string[mazeSize]; mazeX = 2/mazeSize; mazeY = 0.25; mazeZ = 2/mazeSize; } I'm getting a compiler error that says: In file included from model-view.cpp:11: Maze.h:14: error: ISO C++ forbids declaration of ‘string’ with no type Maze.h:14: error: expected ‘;’ before ‘*’ token and the only sense that makes to me is that for some reason it thinks I want string as a variable name not as a type declaration. If anybody could help me out that would be fantastic, been looking this up for a while and its giving me the shits lol. Cheers guys

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• What scenarios are possible where the VS C# compiler would not compile a reference of a reference?

  - by SuperKing

  Hello, I'm probably asking this question wrong (and that may be why Google isn't helping), but here goes: In Visual Studio I am compiling a C# project (let's call it Project A, the startup project) which has a reference to Project B. Project B has a reference to a Project C, so when A gets built, the dlls for B gets placed in the bin directory of A, as does the dll for C (because B requires C, and A requires B). However, I have apparently made some change recently so that the dll for Project C does not go into the bin directory of Project A when rebuilding the solution. I have no idea what I've done to make this happen. I have not modified the setup of the solution itself, and I have only added additional references to the project files. Code wise, I have commented out most of the actual code in Project B that references classes in Project C, but did not remove the reference from the project itself (I don't think this matters). I was told that perhaps the C# compiler was optimizing somehow so that it was not building Project C, but really I'm out of ideas. I would think someone has run into something similar before Any thoughts? Thanks!

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• Why is passing a string literal into a char* argument only sometimes a compiler error?

  - by Brian Postow

  I'm working in a C, and C++ program. We used to be compiling without the make-strings-writable option. But that was getting a bunch of warnings, so I turned it off. Then I got a whole bunch of errors of the form "Cannot convert const char* to char* in argmuent 3 of function foo". So, I went through and made a whole lot of changes to fix those. However, today, the program CRASHED because the literal "" was getting passed into a function that was expecting a char*, and was setting the 0th character to 0. It wasn't doing anything bad, just trying to edit a constant, and crashing. My question is, why wasn't that a compiler error? In case it matters, this was on a mac compiled with gcc-4.0. EDIT: added code: char * host = FindArgDefault("EMailLinkHost", ""); stripCRLF(linkHost, '\n'); where: char *FindArgDefault(char *argName, char *defVal) {// simplified char * val = defVal; return(val); } and void stripCRLF(char *str, char delim) { char *p, *q; for (p = q = str; *p; ++p) { if (*p == 0xd || *p == 0xa) { if (p[1] == (*p ^ 7)) ++p; if (delim == -1) *p = delim; } *q++ = *p; } *q = 0; // DIES HERE } This compiled and ran until it tried to set *q to 0...

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• in haskell, why do I need to specify type constraints, why can't the compiler figure them out?

  - by Steve

  Consider the function, add a b = a + b This works: *Main> add 1 2 3 However, if I add a type signature specifying that I want to add things of the same type: add :: a -> a -> a add a b = a + b I get an error: test.hs:3:10: Could not deduce (Num a) from the context () arising from a use of `+' at test.hs:3:10-14 Possible fix: add (Num a) to the context of the type signature for `add' In the expression: a + b In the definition of `add': add a b = a + b So GHC clearly can deduce that I need the Num type constraint, since it just told me: add :: Num a => a -> a -> a add a b = a + b Works. Why does GHC require me to add the type constraint? If I'm doing generic programming, why can't it just work for anything that knows how to use the + operator? In C++ template programming, you can do this easily: #include <string> #include <cstdio> using namespace std; template<typename T> T add(T a, T b) { return a + b; } int main() { printf("%d, %f, %s\n", add(1, 2), add(1.0, 3.4), add(string("foo"), string("bar")).c_str()); return 0; } The compiler figures out the types of the arguments to add and generates a version of the function for that type. There seems to be a fundamental difference in Haskell's approach, can you describe it, and discuss the trade-offs? It seems to me like it would be resolved if GHC simply filled in the type constraint for me, since it obviously decided it was needed. Still, why the type constraint at all? Why not just compile successfully as long as the function is only used in a valid context where the arguments are in Num? Thank you.

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• Ant and Flex-4 problem, MXMLC.jar not found !

  - by Ali

  Hi all, I updated a flex application from flex 3.5 to flex 4.0. We are using ant for compiling our project and we have a mxmlc task to handle the flex part. After the upgrade, our mxmlc task broke. Here is the task definition: <taskdef resource="flexTasks.tasks"> <classpath> <pathelement path="${FLEX_HOME}/ant/lib/flexTasks.jar"/> <pathelement path="${FLEX_HOME}/lib/flexTasks.jar"/> <fileset dir="${FLEX_HOME}/lib"> <include name="**/*.jar"/> </fileset> </classpath> </taskdef> And here is mxmlc task <mxmlc file="${src}/Main.mxml" output="${build}/main.swf" debug="true" target-player="10" services="../src/main/webapp/WEB-INF/flex/services-config.xml" context-root="/" > <compiler.library-path dir="${lib}"> <include name="*.swc"/> </compiler.library-path> <compiler.library-path dir="${FLEX_HOME}/frameworks/libs"> <include name="*.swc"/> </compiler.library-path> <compiler.library-path dir="${FLEX_HOME}/frameworks/libs/player/10.0"> <include name="*.swc"/> </compiler.library-path> <compiler.library-path dir="${FLEX_HOME}/frameworks/locale"> <include name="**/*"/> </compiler.library-path> </mxmlc> And we are getting: The class not found in jar file: mxmlc.jar I checked the ${FLEX_HOME}/lib folder and I can see the mxmlc.jar file there. I appreciate your comments for resolving this matter, Thanks, -A

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• Visitor pattern and compiler code generation, how to get children attributes?

  - by LeleDumbo

  I'd like to modify my compiler's code generator to use visitor pattern since the current approach must use multiple conditional statement to check the real type of a child before generating the corresponding code. However, I have problems to get children attributes after they're visited. For instance, in binary expression I use this: LHSCode := GenerateExpressionCode(LHSNode); RHSCode := GenerateExpressionCode(RHSNode); CreateBinaryExpression(Self,LHS,RHS); In visitor pattern the visit method is usually void, so I can't get the expression code from LHS and RHS. Keeping shared global variables isn't an option since expression code generation is recursive thus could erase previous values kept in the variables. I'll just show the binary expression as this is the most complicated part (for now): function TLLVMCodeGenerator.GenerateExpressionCode( Expr: TASTExpression): TLLVMValue; var BinExpr: TASTBinaryExpression; UnExpr: TASTUnaryExpression; LHSCode, RHSCode, ExprCode: TLLVMValue; VarExpr: TASTVariableExpression; begin if Expr is TASTBinaryExpression then begin BinExpr := Expr as TASTBinaryExpression; LHSCode := GenerateExpressionCode(BinExpr.LHS); RHSCode := GenerateExpressionCode(BinExpr.RHS); case BinExpr.Op of '<': Result := FBuilder.CreateICmp(ccSLT, LHSCode, RHSCode); '<=': Result := FBuilder.CreateICmp(ccSLE, LHSCode, RHSCode); '>': Result := FBuilder.CreateICmp(ccSGT, LHSCode, RHSCode); '>=': Result := FBuilder.CreateICmp(ccSGE, LHSCode, RHSCode); '==': Result := FBuilder.CreateICmp(ccEQ, LHSCode, RHSCode); '<>': Result := FBuilder.CreateICmp(ccNE, LHSCode, RHSCode); '/\': Result := FBuilder.CreateAnd(LHSCode, RHSCode); '\/': Result := FBuilder.CreateOr(LHSCode, RHSCode); '+': Result := FBuilder.CreateAdd(LHSCode, RHSCode); '-': Result := FBuilder.CreateSub(LHSCode, RHSCode); '*': Result := FBuilder.CreateMul(LHSCode, RHSCode); '/': Result := FBuilder.CreateSDiv(LHSCode, RHSCode); end; end else if Expr is TASTPrimaryExpression then if Expr is TASTBooleanConstant then with Expr as TASTBooleanConstant do Result := FBuilder.CreateConstant(Ord(Value), ltI1) else if Expr is TASTIntegerConstant then with Expr as TASTIntegerConstant do Result := FBuilder.CreateConstant(Value, ltI32) else if Expr is TASTUnaryExpression then begin UnExpr := Expr as TASTUnaryExpression; ExprCode := GenerateExpressionCode(UnExpr.Expr); case UnExpr.Op of '~': Result := FBuilder.CreateXor( FBuilder.CreateConstant(1, ltI1), ExprCode); '-': Result := FBuilder.CreateSub( FBuilder.CreateConstant(0, ltI32), ExprCode); end; end else if Expr is TASTVariableExpression then begin VarExpr := Expr as TASTVariableExpression; with VarExpr.VarDecl do Result := FBuilder.CreateVar(Ident, BaseTypeLLVMTypeMap[BaseType]); end; end; Hope you understand it :)

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