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  • C Preprocessor: #define in C... advice

    - by vikramtheone
    Hi Guys, I'm making a big C project and I have never come across a situation like this before so, I need your advice. What is your opinion? Is it okay to have the constants defined within conditional preprocessors like I have done below or you advise me to do this some other way? Any drawbacks if I do it this way? Regards Vikram #define NUM_OCTAVES_4 //#define NUM_OCTAVES_5 #ifdef NUM_OCTAVES_4 #define OCTAVES 4 const unsigned char borders [4] = {11, 26, 50, 98}; #elif NUM_OCTAVES_5 #define OCTAVES 5 const unsigned char borders [5] = {11, 26, 50, 98, 194}; #endif

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  • GCC problem with raw double type comparisons

    - by Monomer
    I have the following bit of code, however when compiling it with GCC 4.4 with various optimization flags I get some unexpected results when its run. #include <iostream> int main() { const unsigned int cnt = 10; double lst[cnt] = { 0.0 }; const double v[4] = { 131.313, 737.373, 979.797, 731.137 }; for(unsigned int i = 0; i < cnt; ++i) { lst[i] = v[i % 4] * i; } for(unsigned int i = 0; i < cnt; ++i) { double d = v[i % 4] * i; if(lst[i] != d) { std::cout << "error @ : " << i << std::endl; return 1; } } return 0; } when compiled with: "g++ -pedantic -Wall -Werror -O1 -o test test.cpp" I get the following output: "error @ : 3" when compiled with: "g++ -pedantic -Wall -Werror -O2 -o test test.cpp" I get the following output: "error @ : 3" when compiled with: "g++ -pedantic -Wall -Werror -O3 -o test test.cpp" I get no errors when compiled with: "g++ -pedantic -Wall -Werror -o test test.cpp" I get no errors I do not believe this to be an issue related to rounding, or epsilon difference in the comparison. I've tried this with Intel v10 and MSVC 9.0 and they all seem to work as expected. I believe this should be nothing more than a bitwise compare. If I replace the if-statement with the following: if (static_cast<long long int>(lst[i]) != static_cast<long long int>(d)), and add "-Wno-long-long" I get no errors in any of the optimization modes when run. If I add std::cout << d << std::endl; before the "return 1", I get no errors in any of the optimization modes when run. Is this a bug in my code, or is there something wrong with GCC and the way it handles the double type?

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  • Working with foreign keys - cannot insert

    - by Industrial
    Hi everyone! Doing my first tryouts with foreign keys in a mySQL database and are trying to do a insert, that fails for this reason: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails Does this mean that foreign keys restrict INSERTS as well as DELETES and/or UPDATES on each table that is enforced with foreign keys relations? Thanks! Updated description: Products ---------------------------- id | type ---------------------------- 0 | 0 1 | 3 ProductsToCategories ---------------------------- productid | categoryid ---------------------------- 0 | 0 1 | 1 Product table has following structure CREATE TABLE IF NOT EXISTS `alpha`.`products` ( `id` MEDIUMINT UNSIGNED NOT NULL AUTO_INCREMENT , `type` TINYINT(2) UNSIGNED NOT NULL DEFAULT 0 , PRIMARY KEY (`id`) , CONSTRAINT `prodsku` FOREIGN KEY (`id` ) REFERENCES `alpha`.`productsToSku` (`product` ) ON DELETE CASCADE, ON UPDATE CASCADE) ENGINE = InnoDB;

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  • Programmatically create static arrays at compile time in C++

    - by Hippicoder
    One can define a static array at compile time as follows: const std::size_t size = 5; unsigned int list[size] = { 1, 2, 3, 4, 5 }; Question 1 - Is it possible by using various kinds of metaprogramming techniques to assign these values "programmatically" at compile time? Question 2 - Assuming all the values in the array are to be the same barr a few, is it possible to selectively assign values at compile time in a programmatic manner? eg: const std::size_t size = 7; unsigned int list[size] = { 0, 0, 2, 3, 0, 0, 0 }; Solutions using C++0x are welcome The array may be quite large, few hundred elements long The array for now will only consist of POD types It can also be assumed the size of the array will be known beforehand, in a static compile-time compliant manner. Solutions must be in C++ (no script or codegen based solutions)

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  • Why do i get segfault at the end of the application after everything's been done properly ?

    - by VaioIsBorn
    #include <string.h> #include <stdlib.h> #include <stdio.h> int main(void) { unsigned char *stole; unsigned char pass[] = "m4ak47"; printf("Vnesi password: \t"); scanf("%s", stole); if(strncmp(stole, pass, sizeof(pass)) != 0) { printf("wrong password!\n"); exit(0); } else printf("Password correct\n"); printf("some stuf here...\n\n"); return 0; } This program is working nice, but with one problem - if the password is correct then it DOES do the printing of 'some stuf here...' but it also shows me segmentation fault error at the end. Why ?

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  • SQL select all items of an owner from an item-to-owner table

    - by kdobrev
    I have a table bike_to_owner. I would like to select current items owned by a specific user. Table structure is CREATE TABLE IF NOT EXISTS `bike_to_owner` ( `bike_id` int(10) unsigned NOT NULL, `user_id` int(10) unsigned NOT NULL, `last_change_date` date NOT NULL, PRIMARY KEY (`bike_id`,`user_id`,`last_change_date`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci; In the profile page of the user I would like to display all his/her current possessions. I wrote this statement: SELECT `bike_id`,`user_id`,max(last_change_date) FROM `bike_to_owner` WHERE `user_id` = 3 group by `last_change_date` but i'm not quite sure it works correctly in all cases. Can you please verify this is correct and if not suggest me something better. Using php/mysql. Thanks in advance!

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  • Assigning large UInt32 constants in VB.Net

    - by Kumba
    I inquired on VB's erratic behavior of treating all numerics as signed types back in this question, and from the accepted answer there, was able to get by. Per that answer: Visual Basic Literals Also keep in mind you can add literals to your code in VB.net and explicitly state constants as unsigned. So I tried this: Friend Const POW_1_32 As UInt32 = 4294967296UI And VB.NET throws an Overflow error in the IDE. Pulling out the integer overflow checks doesn't seem to help -- this appears to be a flaw in the IDE itself. This, however, doesn't generate an error: Friend Const POW_1_32 As UInt64 = 4294967296UL So this suggests to me that the IDE isn't properly parsing the code and understanding the difference between Int32 and UInt32. Any suggested workarounds and/or possible clues on when MS will make unsigned data types intrinsic to the framework instead of the hacks they currently are?

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  • Use format strings that contain %1, %2 etc. instead of %d, %s etc. - Linux, C++

    - by rursw1
    Hello, As a follow-up of this question (Message compiler replacement in Linux gcc), I have the following problem: When using MC.exe on Windows for compiling and generating messages, within the C++ code I call FormatMessage, which retrieves the message and uses the va_list *Arguments parameter to send the varied message arguments. For example: messages.mc file: MessageId=1 Severity=Error SymbolicName=MULTIPLE_MESSAGE_OCCURED Language=English message %1 occured %2 times. . C++ code: void GetMsg(unsigned int errCode, wstring& message,unsigned int paramNumber, ...) { HLOCAL msg; DWORD ret; LANGID lang = GetUserDefaultLangID(); try { va_list argList; va_start( argList, paramNumber ); const TCHAR* dll = L"MyDll.dll"; _hModule = GetModuleHandle(dll); ret =::FormatMessage( FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_HMODULE|FORMAT_MESSAGE_IGNORE_INSERTS, _hModule, errCode, lang, (LPTSTR) &msg, 0, &argList ); if ( 0 != ret ) { unsigned int count = 0 ; message = msg; if (paramNumber>0) { wstring::const_iterator iter; for (iter = message.begin();iter!=message.end();iter++) { wchar_t xx = *iter; if (xx ==L'%') count++; } } if ((count == paramNumber) && (count >0)) { ::LocalFree( msg ); ret =::FormatMessage( FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_HMODULE, _hModule, errCode, GetUserDefaultLangID(), (LPTSTR) &msg, 0, &argList ); } else if (count != paramNumber) { wstringstream tmp; wstring messNumber; tmp << (errCode & 0xFFFF); tmp >> messNumber; message = message +L"("+ messNumber + L"). Bad Format String. "; } } ::LocalFree( msg ); } catch (...) { message << L"last error: " << GetLastError(); } va_end( argList ); } Caller code: wstring message; GetMsg(MULTIPLE_MESSAGE_OCCURED, message,2, "Error message", 5); Now, I wrote a simple script to generate a .msg file from the .mc file, and then I use gencat to generate a catalog from it. But is there a way to use the formatted strings as they contain %1, %2, etc. and NOT the general (%d, %s...) format? Please note, that the solution has to be generic enough for each possible message with each posible types\ arguments order... Is it possible at all? Thank you.

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  • Calling assembly in GCC????

    - by rbr200
    include static inline uint xchg(volatile unsigned int *addr, unsigned int newval) { uint result; asm volatile("lock; xchgl %0, %1" : "+m" (*addr), "=a" (result) : "1" (newval) : "cc"); return result; } Can some one tell me what this code does exactly. I mean I have an idea or the parts of this command. "1" newval is the input, "=a" is to flush out its previous value and update it. "m" is for the memory operation but I am confused about the functionality of this function. What does the "+m" sign do? Does this function do sumthing like m=a; m = newval; return a

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  • Is there any way to determine what type of memory the segments returned by VirtualQuery() are?

    - by bdbaddog
    Greetings, I'm able to walk a processes memory map using logic like this: MEMORY_BASIC_INFORMATION mbi; void *lpAddress=(void*)0; while (VirtualQuery(lpAddress,&mbi,sizeof(mbi))) { fprintf(fptr,"Mem base:%-10x start:%-10x Size:%-10x Type:%-10x State:%-10x\n", mbi.AllocationBase, mbi.BaseAddress, mbi.RegionSize, mbi.Type,mbi.State); lpAddress=(void *)((unsigned int)mbi.BaseAddress + (unsigned int)mbi.RegionSize); } I'd like to know if a given segment is used for static allocation, stack, and/or heap and/or other? Is there any way to determine that?

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  • Visual C++ 2008 Intellisense is not displaying DocXml comments

    - by DavidTM
    In Visual C++ 2008, I have documented a method with DocXML: /// <summary>Function to generate and map channel.</summary> /// <param name="a_cfi">Raw CFI (1, 2 or 3)</param> /// <param name="a_ns">Slot number in frame</param> static void myFunc(unsigned a_cfi, unsigned a_ns); Intellisense displays this, but it displays the actual tags (i.e. precisely as shown above) instead of recognizing the tags and formatting the text accordingly. How can I fix this please?

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  • Floating point precision nuances.

    - by user247077
    Hi, I found this code in NVIDIA's cuda SDK samples. void computeGold( float* reference, float* idata, const unsigned int len) { reference[0] = 0; double total_sum = 0; unsigned int i; for( i = 1; i < len; ++i) { total_sum += idata[i-1]; reference[i] = idata[i-1] + reference[i-1]; } // Here it should be okay to use != because we have integer values // in a range where float can be exactly represented if (total_sum != reference[i-1]) printf("Warning: exceeding single-precision accuracy. Scan will be inaccurate.\n"); } (C) Nvidia Corp Can somebody please tell me a case where the warning would be printed, and most importantly, why. Thank you very much.

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  • Select *, max(date) works in phpMyAdmin but not in my code

    - by kdobrev
    OK, my statement executes well in phpMyAdmin, but not how I expect it in my php page. This is my statement: SELECT egid , group_name , limit , MAX( date ) FROM employee_groups GROUP BY egid ORDER BY egid DESC ; This is may table: CREATE TABLE employee_groups ( egid int(10) unsigned NOT NULL, date date NOT NULL, group_name varchar(50) NOT NULL, limit smallint(5) unsigned NOT NULL, PRIMARY KEY (egid,date) ) ENGINE=MyISAM DEFAULT CHARSET=cp1251; I want to extract the most recent list of groups, e.g. if a group has been changed I want to have only the last change. And I need it as a list (all groups).

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  • c++ normalizing data sizes across systems

    - by Bocochoco
    I have a struct with three variables: two unsigned ints and an unsigned char. From my understanding, a c++ char is always 1 byte regardless of what operating system it is on. The same can't be said for other datatypes. I am looking for a way to normalize POD's so that when saved into a binary file, the resulting file is readable on any operating system that the code is compiled for. I changed my struct to use a 1-byte alignment by adding #pragma as follows: #pragma pack(push, 1) struct test { int a; } #pragma pack(pop) but that doesn't necessarily mean that int a is exactly 4 bytes on every os, I don't think? Is there a way to ensure that a file saved from my code will always be readable?

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  • Unique constraint with nullable column

    - by Álvaro G. Vicario
    I have a table that holds nested categories. I want to avoid duplicate names on same-level items (i.e., categories with same parent). I've come with this: CREATE TABLE `category` ( `category_id` int(10) unsigned NOT NULL AUTO_INCREMENT, `category_name` varchar(100) NOT NULL, `parent_id` int(10) unsigned DEFAULT NULL, PRIMARY KEY (`category_id`), UNIQUE KEY `category_name_UNIQUE` (`category_name`,`parent_id`), KEY `fk_category_category1` (`parent_id`,`category_id`), CONSTRAINT `fk_category_category1` FOREIGN KEY (`parent_id`) REFERENCES `category` (`category_id`) ON DELETE SET NULL ON UPDATE CASCADE ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_spanish_ci Unluckily, category_name_UNIQUE does not enforce my rule for root level categories (those where parent_id is NULL). Is there a reasonable workaround?

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  • Using pow() for large number

    - by g4ur4v
    I am trying to solve a problem, a part of which requires me to calculate (2^n)%1000000007 , where n<=10^9. But my following code gives me output "0" even for input like n=99. Is there anyway other than having a loop which multilplies the output by 2 every time and finding the modulo every time (this is not I am looking for as this will be very slow for large numbers). #include<stdio.h> #include<math.h> #include<iostream> using namespace std; int main() { unsigned long long gaps,total; while(1) { cin>>gaps; total=(unsigned long long)powf(2,gaps)%1000000007; cout<<total<<endl; } }

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  • cannot convert ‘mcontext_t*’ to ‘sigcontext*’ in assignment

    - by user353573
    i have checked asm/ucontext.h it should be sigcontext, but why pop up the error message cannot convert ‘mcontext_t*’ to ‘sigcontext*’ in assignment #include <stdio.h> #include <signal.h> #include <asm/ucontext.h> static unsigned long target; void handler(int signum, siginfo_t *siginfo, void *uc0){ struct ucontext *uc; struct sigcontext *sc; uc = (struct ucontext *)uc0; sc = &uc->uc_mcontext; sc->eip = target; } struct ucontext { unsigned long uc_flags; struct ucontext *uc_link; stack_t uc_stack; struct sigcontext uc_mcontext; sigset_t uc_sigmask; /* mask last for extensibility */ };

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  • What is wrong with this C++ Code ?

    - by mr.bio
    Hi .. i am a beginner and i have a problem : this code doesnt compile : main.cpp: #include <stdlib.h> #include "readdir.h" #include "mysql.h" #include "readimage.h" int main(int argc, char** argv) { if (argc>1){ readdir(argv[1]); // test(); return (EXIT_SUCCESS); } std::cout << "Bitte Pfad angeben !" << std::endl ; return (EXIT_FAILURE); } readimage.cpp #include <Magick++.h> #include <iostream> #include <vector> using namespace Magick; using namespace std; void readImage(std::vector<string> &filenames) { for (unsigned int i = 0; i < filenames.size(); ++i) { try { Image img("binary/" + filenames.at(i)); for (unsigned int y = 1; y < img.rows(); y++) { for (unsigned int x = 1; x < img.columns(); x++) { ColorRGB rgb(img.pixelColor(x, y)); // cout << "x: " << x << " y: " << y << " : " << rgb.red() << endl; } } cout << "done " << i << endl; } catch (Magick::Exception & error) { cerr << "Caught Magick++ exception: " << error.what() << endl; } } } readimage.h #ifndef _READIMAGE_H #define _READIMAGE_H #include <Magick++.h> #include <iostream> #include <vector> #include <string> using namespace Magick; using namespace std; void readImage(vector<string> &filenames) #endif /* _READIMAGE_H */ If want to compile it with this code : g++ main.cpp Magick++-config --cflags --cppflags --ldflags --libs readimage.cpp i get this error message : main.cpp:5: error: expected initializer before ‘int’ i have no clue , why ? :( Can somebody help me ? :)

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  • Question about inserting assembly code in C++

    - by Bruce
    I am working on VC++ compiler. I want to accomplish the following The variables s.AddrFrame.Offset and s.AddrStack.Offset contain the value of EBP and ESP respectively. I want to extract the value of old EBP and the return address. Assuming the address EBP + 1 contains the old 32 bit EBP value and EBP + 5 the return address I wrote the following code: unsigned int old_ebp = 0; unsigned int ret_addr = 0; __asm{ mov old_ebp, DWORD PTR [s.AddrFrame.Offset + 1] mov ret_addr, DWORD PTR [s.AddrStack.Offset + 5] } But this is not compiling xxxx.cpp(1130) : error C2415: improper operand type Please Help

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  • Does MySQL allow two primary keys on one table?

    - by Bharanikumar
    CREATE TABLE Orders -> ( -> ID SMALLINT UNSIGNED NOT NULL, -> ModelID SMALLINT UNSIGNED NOT NULL, -> Descrip VARCHAR(40), -> PRIMARY KEY (ID, ModelID) -> ); Basically, this appears to me to be creating two primary key on one table. Is that correct? I thought that we could create a number of unique keys in one table, but only one primary key. How is it that my system is allowing the creation of multiple primary keys? Please advise: what are the rules governing this?

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  • How can I convert floating point values in text to binary using Perl?

    - by YoDar
    I have text file looks like that: float a[10] = { 7.100000e+000 , 9.100000e+000 , 2.100000e+000 , 1.100000e+000 , 8.200000e+000 , 7.220000e+000 , 7.220000e+000 , 7.222000e+000 , 1.120000e+000 , 1.987600e+000 }; unsigned int col_ind[10] = { 1 , 4 , 3 , 4 , 5 , 2 , 3 , 4 , 1 , 5 }; Now, I want to convert each array (float / unsigned int) to different binary files - big endian type. Binary file for all float values and binary file for all integer values. What is the simple way to do it in Perl, consider I have over 2 millon elements in each array?

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  • How to find the differences between the values of a specific column based on a key?

    - by Holicreature
    I've two tables as purchase_details and invoice_details and i want to store the inventory/stock of each product from the data of these two tables. structure of purchase_details. 'pid', 'int(10)' 'product_id', 'int(10)' 'quantity', 'float(8,2)' 'amount', 'float(12,2)' 'expiry_date', 'date' structure of purchase_details. 'invoice_id', 'int(10) unsigned' 'product_id', 'int(10) unsigned' 'quantity', 'float(10,2)' 'price', 'float(12,2)' i want to calculate the total quantity of remaining stock (quantity of sum of products from purchase_details - quantity of sum of products from invoice_details). Product_id is would be same for the two tables. how can i proceed?

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  • Copy method optimization in compilers

    - by Dženan
    Hi All! I have the following code: void Stack::operator =(Stack &rhs) { //do the actual copying } Stack::Stack(Stack &rhs) //copy-constructor { top=NULL; //initialize this as an empty stack (which it is) *this=rhs; //invoke assignment operator } Stack& Stack::CopyStack() { return *this; //this statement will invoke copy contructor } It is being used like this: unsigned Stack::count() { unsigned c=0; Stack copy=CopyStack(); while (!copy.empty()) { copy.pop(); c++; } return c; } Removing reference symbol from declaration of CopyStack (returning a copy instead of reference) makes no difference in visual studio 2008 (with respect to number of times copying is invoked). I guess it gets optimized away - normally it should first make a copy for the return value, then call assignment operator once more to assign it to variable sc. What is your experience with this sort of optimization in different compilers? Regards, Dženan

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