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  • Two '==' equality operators in same 'if' condition are not working as intended.

    - by Manav MN
    I am trying to establish equality of three equal variables, but the following code is not printing the obvious true answer which it should print. Can someone explain, how the compiler is parsing the given if condition internally? #include<stdio.h> int main() { int i = 123, j = 123, k = 123; if ( i == j == k) printf("Equal\n"); else printf("NOT Equal\n"); return 0; } Output: manav@workstation:~$ gcc -Wall -pedantic calc.c calc.c: In function ‘main’: calc.c:5: warning: suggest parentheses around comparison in operand of ‘==’ manav@workstation:~$ ./a.out NOT Equal manav@workstation:~$ EDIT: Going by the answers given below, is the following statement okay to check above equality? if ( (i==j) == (j==k))

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  • Block until an event has completed.

    - by robUK
    Hello, gcc 4.4.2 c89 I have a function that has to run (config_relays). It make a call to a API function called set_relay, then the code has to wait before continuing until the event for set_relay event has completed. The set_relay is any Async call. i.e. void run_processes() { switch() { case EV_RELAY_SET: break; } } void config_relays() { set_relay(); /* Wait until EV_RELAY_SET has fired */ /* Cannot do init_relay until set_relay event has fired - has to block here */ init_relay(); } I guess I could put the init_relay() in the switch. However, that event is used for other things and not just for initializing the relay. I would really like to handle everything in the config_relays function. In C# you can do this by using autoreset. Does C have anything like that. Many thanks for any advice,

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  • nul terminating a int array

    - by robUK
    Hello, gcc 4.4.4 c89 I was just experimenting with a int array. And something just came to my mind. Can I nul terminate it. For example, I am using a 0 to nul terminate. However, 0 could well be a valid value in this array. The code below will terminate after the 5. Even though I mean 0 to be a valid number. However, I could specify the size of the array. But in this case, I don't want to this as I am just interested in this particular problem. Many thanks for any advice, #include <stdio.h> static void test(int *p); int main(void) { int arr[] = {30, 450, 14, 5, 0, 10, '\0'}; test(arr); return 0; } static void test(int *p) { while(*p) { printf("Array values [ %d ]\n", *p++); } }

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  • cmake and visual studio

    - by robUK
    Hello, gcc 4.4.2 / Visual Studio C++ 2008 I have been using cmake on linux, without any problems. Now I have ported by application to run on windows. I generated the solution files using cmake -G "Visual Studio 9 2008 ../src" However, I know that cmake only creates a Makefile that is used by the compiler to build your application. I open my solution in Visual Studio, I press the F7 key to compile. I am wondering does it actually use the Makefile that was generated by cmake? Or it is just compiling the application like any normal visual studio program? Many thanks for any advice,

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  • How to set that compiler flag?

    - by mystify
    Shark told me this: This instruction is the start of a loop that is not aligned to a 16-byte address boundary. For optimal performance, you should align the start of a hot loop using a compiler directive. With gcc 3.3 or later, use the -falign-loops=16 compiler flag. for (int i=0; i < 4; i++) { // line with the info //...code } How would I set that flag, and does it really improve performance?

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  • Java bytecode compiler benchmarks

    - by Dave Jarvis
    Q.1. What free compiler produces the fastest executable Java bytecode? Q.2. What free virtual machine executes Java bytecode the fastest (on 64-bit multi-core CPUs)? Q.3. What other (currently active) compiler projects are missing from this list: http://www.ibm.com/developerworks/java/jdk/ http://gcc.gnu.org/java/ http://openjdk.java.net/groups/compiler/ http://java.sun.com/javase/downloads/ http://download.eclipse.org/eclipse/downloads/ Q.4. What performance improvements can compilers do that JITs cannot (or do not)? Q.5. Where are some recent benchmarks, comparisons, or shoot-outs (for Q1 or Q2)? Thank you!

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  • How do I generate different yyparse functions from lex/yacc for use in the same program?

    - by th
    Hi, I want to generate two separate parsing functions from lex/yacc. Normally yacc gives you a function yyparse() that you can call when you need to do some parsing, but I need to have several different yyparses each associated with different lexers and grammars. The man page seems to suggest the -p (prefix) flag, but this didn't work for me. I got errors from gcc that indicated that yylval was not properly being relabeled (i.e. it claims that several different tokens are not defined). Does anyone know the general rpocedure for generating these separate functions? thanks

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  • VS 11 with std::future - Is this a bug?

    - by cooky451
    I recently installed the Visual Studio 11 Developer Preview. While playing with threads and futures, I came around this setup: #include <future> #include <iostream> int foo(unsigned a, unsigned b) { return 5; } int main() { std::future<int> f = std::async(foo, 5, 7); std::cout << f.get(); } So, very simple. But since there are two arguments for "foo", VS 11 doesn't want to compile it. (However, g++ does: http://ideone.com/ANrPj) (The runtime error is no problem: std::future exception on gcc experimental implementation of C++0x) (VS 11 errormessage: http://pastebin.com/F9Xunh2s) I'm a little confused right now, since this error seems extremely obvious to me, even if it is a developer preview. So my questions are: Is this code correct according to the C++11 standard? Is this bug already known/reported?

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  • inheritance and hidden overloads

    - by Caspin
    The following code doesn't compile. struct A {}; struct B {}; class Base { public: virtual void method( A param ) { } virtual void method( B param ) = 0; }; class Derived : public Base { public: //using Base::method; void method( B param ) { } }; int main() { Derived derived; derived.method(A()); } The compiler can't find the overload of method() that has an A parameter. The 'fix' is to add a using declaration in the derived class. My question is why. What is the rational for a weird language rule like this? I verified the error in both GCC and Comeau, so I assume this isn't a compiler bug but a feature of the language. Comeau at least gives me this warning: "ComeauTest.c", line 10: warning: overloaded virtual function "Base::method" is only partially overridden in class "Derived" class Derived : public Base ^

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  • arm-apple-darwin9-g++ Bus error problem

    - by overboming
    I want to create a mobilesubstrate plugin for iPhone OS 3.2 or I tried to setup toolchain on the iPad device. I have installed the iphone-gcc_4.2-20090304-1-9_iphoneos-arm package and all the relevant packages from Cydia, but when it comes to compiling the simplest source file shows the following error: arm-apple-darwin9-g++ -I /var/toolchain/sys/ -c -dynamiclib ExampleHookLibrary.mm -o ExampleHookLibrary.o arm-apple-darwin9-g++: Internal error: Bus error (program cc1objplus) Please submit a full bug report. See <URL:http://developer.apple.com/bugreporter> for instructions. make: *** [ExampleHookLibrary.o] Error 1 Is it because the iphone-gcc doesn't yet support this device or am I missing anything here? Thanks.

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  • for loop in #define

    - by hspim
    #include <stdio.h> #define UNITS {'*', '#', '%', '!', '+', '$', '=', '-'} #define PrintDigit(c, d) (for (i=0; i < c ; i++)putchar(unit[d]);) char unit[] = UNITS; //void PrintDigit(c, element) { // int i; // for (i=0; i < c ; i++) // putchar(unit[element]); //} int main( ) { int i, element=4; PrintDigit(10, element); putchar('\n'); return 0; } I have the function here PrintDigit() which works as expected. When attempting to turn the function into a #define however gcc keeps throwing a syntax error on the for loop. Any idea what the problem is?

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  • Should you remove all warnings in your Verilog or VHDL design? Why or why not?

    - by Brian Carlton
    In (regular) software I have worked at companies where the gcc option -Wall is used to show all warnings. Then they need to be dealt with. With non-trivial FPGA/ASIC design in Verilog or VHDL there are often many many warnings. Should I worry about all of them? Do you have any specific techniques to suggest? My flow is mainly for FPGAs (Altera and Xilinx in particular), but I assume the same rules would apply to ASIC design, possibly more so due to the inability to change the design after it is built.

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  • Problems compiling an external library on linux...

    - by Kris
    So I am trying to compile the libssh2 library on linux, but when I try to compile the example it comes up with a lot of errors, and even though I include the headerfile it asks for, it still asks for it. Here are the error messages and the resulting messages: ~/ gcc -include /home/Roosevelt/libssh2-1.2.5/src/libssh2_config.h -o lolbaise /home/Roosevelt/libssh2-1.2.5/example/scp.c /home/Roosevelt/libssh2-1.2.5/example/scp.c:7:28: error: libssh2_config.h: No such file or directory /home/Roosevelt/libssh2-1.2.5/example/scp.c: In function 'main': /home/Roosevelt/libssh2-1.2.5/example/scp.c:39: error: storage size of 'sin' isn't known /home/Roosevelt/libssh2-1.2.5/example/scp.c:81: error: 'AF_INET' undeclared (first use in this function) /home/Roosevelt/libssh2-1.2.5/example/scp.c:81: error: (Each undeclared identifier is reported only once /home/Roosevelt/libssh2-1.2.5/example/scp.c:81: error: for each function it appears in.) /home/Roosevelt/libssh2-1.2.5/example/scp.c:81: error: 'SOCK_STREAM' undeclared (first use in this function) /home/Roosevelt/libssh2-1.2.5/example/scp.c:87: error: invalid application of 'sizeof' to incomplete type 'struct sockaddr_in'

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  • MinGW linking problem

    - by Tobias Langner
    I have a linking problem with MinGW. These are the calls: g++ -enable-stdcall-fixup -Wl,-enable-auto-import -Wl,-enable-runtime-pseudo-reloc -mthreads -Wl -Wl,-subsystem,windows -o debug/Simulation.exe debug/LTNetSender.o debug/main.o debug/simulation.o debug/moc_simulation.o -L'c:/Programmieren/Qt/4.5.2/lib' -lmingw32 -lqtmaind -LC:\Programmieren\Qt\boost_1_39_0\distrib\lib -LC:\Programmieren\MinGW\lib -llibboost_system-mgw34-mt -llibws2_32 -lQtSqld4 -lQtGuid4 -lQtNetworkd4 -lQtCored4 C:\Programmieren\MinGW\bin\..\lib\gcc\mingw32\3.4.5\..\..\..\..\mingw32\bin\ ld.exe: cannot find -llibws2_32 The MinGW library directory is included in the library path and libws2_32.a is in this directory. Why isn't the linker finding the library?

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  • negative precision values in ostream

    - by daz-fuller
    This is more of a question of curiosity but does anyone know how negative precision values are handled in C++? For example: double pi = 3.14159265; cout.precision(-10); cout.setf(ios::fixed, ios::floatfield); cout << pi << endl; I've tried this out and using GCC and it seems that the precision value is ignored but I was curious if there is some official line on what happens in this situation.

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  • Problem linking SDL_Image against libpng

    - by Tim Jones
    I'm trying to compile SDL_Image 1.2.10 with MinGW + MSys (gcc 4.5.0) on Windows, I have compiled all the requires libs (zlib 1.2.5, libpng 1.4.2, libjpeg 8a, libtiff 3.9.2). SDL_Image compiles fine, but fails to link to libpng, throwing .libs/IMG_png.o:IMG_png.c:(.text+0x16): undefined reference errors on various png structs. If I run ./configure --prefix=/mingw --disable-png for SDL_Image, it compiles and links against the other libs just fine. I have tried older versions of libpng (1.2.43), but they also caused SDL_Image to throw the same errors.

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  • What build param(s) to use so VS 2010 can gen .obj & link .objs but NOT create an .exe?

    - by Csourcecode
    Question title pretty much asks it all. I know I could set the project to be a .lib build and have it fail to build/link a .lib .... and the .objs tend to be in the appropriate config dir That seems like a shi*-a** backdoor way to get VS to gen objs Is there a flag/param I can set somewhere in the property sheet properties/options for Visual Studio so it links what it needs to & gens the respective objs for each source file? It's so freaking easy to just gen object files using gcc (and link in appropriate lib routines WITHOUT creating an executable) ... I'm sure I could also hack up a custom build rule but that seems like overkill [and since I'm not up to speed on the build rules for whatever version of make VS 2010 is using it's easier to ask someone else here for the simple solution]

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  • Compiler/Linking Error: Freedup

    - by nym
    I've been trying to compile a program for hardlinking duplicate files called freedup. I did try to email the author/maintainer of the program, but it's been a long time and I haven't heard anything back from him. I'm trying to compile the program from a cygwin environment using the latest stable versions of gcc (3.4.4-999) and make (3.81-2). I've tried deleting all the object files and running make, but I always get the following error: freedup.o: In function 'main': /home/[user]/freedup-1.5/freedup.c:1791: undefined reference to '_hashed' collect2: ld returned 1 exit status make: * * * [freedup] Error 1 I did take a look at the source code and saw that the "hashed" function is an inline function (which I didn't think had to be declared outside of the source file... but that's just what I gathered from some preliminary googling). If anyone would be kind enough to try compiling this program in a windows environment and has any luck, I'd really appreciate it. Thanks The direct link for the source files is: http://freedup.org/freedup-1.5-3-src.tgz

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  • Problem building PyGTK on CentOS

    - by Marcelo Cantos
    I am trying to build PyGTK on CentOS for a non-standard Python (2.6, vs the out-of-the-box 2.4). It requires that I first build pygobject. pygobject-2.18.0 fails at the configure step. The error messages is as follows: checking for GLIB - version >= 2.14.0... no *** Could not run GLIB test program, checking why... *** The test program failed to compile or link. See the file config.log for the *** exact error that occured. This usually means GLIB is incorrectly installed. configure: error: maybe you want the pygobject-2-4 branch? I have downloaded, built and successfully installed glib. The config.log file contains the following output: configure:6893: gcc -E conftest.c conftest.c:13:28: error: ac_nonexistent.h: No such file or directory What am I doing wrong?

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  • C++ defines for a 'better' Release mode build in VS

    - by darid
    I currently use the following preprocessor defines, and various optimization settings: WIN32_LEAN_AND_MEAN VC_EXTRALEAN NOMINMAX _CRT_SECURE_NO_WARNINGS _SCL_SECURE_NO_WARNINGS _SECURE_SCL=0 _HAS_ITERATOR_DEBUGGING=0 My question is what other things do fellow SOers use, add, define, in order to get a Release Mode build from VS C++ (2008,2010) to be as performant as possible? btw, I've tried PGO etc, it does help a bit but nothing that comes to parity, also I'm not using streams, the C++ i'm talking about its more like C but making use of templates and STL algorithms. As it stands now very simple code segments flop when compared to what GCC produces on say an equivalent x86 machine running linux (2.6+ kernel) using 02. Side-Note: I believe a lot of the issues relate directly to the STL version (Dinkum) provided by MS. Could people please elaborate on experiences using STLPort etc with VS C++.

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  • Undefined symbols when attempting to use CoverStory with iPhone app: _vproc_transaction_end

    - by dbarker
    After following these steps to set up an iphone project with CoverStory, my build fails with two linker errors. Undefined symbols: "_vproc_transaction_end", referenced from: _gcov_exit in libgcov.a(_gcov.o) _vproc_transaction_end$non_lazy_ptr in libgcov.a(_gcov.o) (maybe you meant: _vproc_transaction_end$non_lazy_ptr) "_vproc_transaction_begin", referenced from: ___gcov_init in libgcov.a(_gcov.o) _vproc_transaction_begin$non_lazy_ptr in libgcov.a(_gcov.o) (maybe you meant: _vproc_transaction_begin$non_lazy_ptr) ld: symbol(s) not found collect2: ld returned 1 exit status The second error is similar to above, except for _vproc_transaction_begin. I'm using Xcode 3.2, GCC 4.2 on Snow Leopard. Any ideas what I'm missing?

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  • Use WM_COPYDATA to send data between processes

    - by Charles Gargent
    I wish to send text between processes. I have found lots of examples of this but none that I can get working. Here is what I have so far: for the sending part: COPYDATASTRUCT CDS; CDS.dwData = 1; CDS.cbData = 8; CDS.lpData = NULL; SendMessage(hwnd, WM_COPYDATA , (WPARAM)hwnd, (LPARAM) (LPVOID) &CDS); the receiving part: case WM_COPYDATA: COPYDATASTRUCT* cds = (COPYDATASTRUCT*) lParam; I dont know how to construct the COPYDATASTRUCT, I have just put something in that seems to work. When debugging the WM_COPYDATA case is executed, but again I dont know what to do with the COPYDATASTRUCT. I would like to send text between the two processes. As you can probably tell I am just starting out, I am using GNU GCC Compiler in Code::Blocks, I am trying to avoid MFC and dependencies.

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  • Linux program in FreeBSD

    - by Alex Farber
    Trying to run my program in FreeBSD OS, I have the following results: $ ./myprogram ELF binary type "0" not known ./myprogram: 1: Syntax error: "&" unexpected (expecting ")") $ file myprogram myprogram: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.15, not stripped The program is built In GCC on Ubuntu computer. What can I do? Can I build the program for FreeBSD on my Ubuntu computer by changing some build options, or I need to build it in FreeBSD OS? Maybe there is some way to convert executable to format recognized by FreeBSD?

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  • Windows API calls from assembly while minimizing program size

    - by takteek
    I'm trying to write a program in assembly and make the resulting executable as small as possible. Some of what I'm doing requires windows API calls to functions such as WriteProcessMemory. I've had some success with calling these functions, but after compiling and linking, my program comes out in the range of 14-15 KB. (From a source of less than 1 KB) I was hoping for much, much less than that. I'm very new to doing low level things like this so I don't really know what would need to be done to make the program smaller. I understand that the exe format itself takes up quite a bit of space. Can anything be done to minimize that? I should mention that I'm using NASM and GCC but I can easily change if that would help.

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  • Why is .NET faster than C++ in this case?

    - by acidzombie24
    -edit- I LOVE SLaks comment. "The amount of misinformation in these answers is staggering." :D Calm down guys. Pretty much all of you were wrong. I DID make optimizations. It turns out whatever optimizations I made wasn't good enough. I ran the code in GCC using gettimeofday (I'll paste code below) and used g++ -O2 file.cpp and got slightly faster results then C#. Maybe MS didn't create the optimizations needed in this specific case but after downloading and installing mingw I was tested and found the speed to be near identical. Justicle Seems to be right. I could have sworn I use clock on my PC and used that to count and found it was slower but problem solved. C++ speed isn't almost twice as slower in the MS compiler. When my friend informed me of this I couldn't believe it. So I took his code and put some timers onto it. Instead of Boo I used C#. I constantly got faster results in C#. Why? The .NET version was nearly half the time no matter what number I used. C++ version: #include <iostream> #include <stdio.h> #include <intrin.h> #include <windows.h> using namespace std; int fib(int n) { if (n < 2) return n; return fib(n - 1) + fib(n - 2); } int main() { __int64 time = 0xFFFFFFFF; while (1) { int n; //cin >> n; n = 41; if (n < 0) break; __int64 start = __rdtsc(); int res = fib(n); __int64 end = __rdtsc(); cout << res << endl; cout << (float)(end-start)/1000000<<endl; break; } return 0; } C# version: using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Runtime.InteropServices; using System.ComponentModel; using System.Threading; using System.IO; using System.Diagnostics; namespace fibCSTest { class Program { static int fib(int n) { if (n < 2)return n; return fib(n - 1) + fib(n - 2); } static void Main(string[] args) { //var sw = new Stopwatch(); //var timer = new PAB.HiPerfTimer(); var timer = new Stopwatch(); while (true) { int n; //cin >> n; n = 41; if (n < 0) break; timer.Start(); int res = fib(n); timer.Stop(); Console.WriteLine(res); Console.WriteLine(timer.ElapsedMilliseconds); break; } } } } GCC version: #include <iostream> #include <stdio.h> #include <sys/time.h> using namespace std; int fib(int n) { if (n < 2) return n; return fib(n - 1) + fib(n - 2); } int main() { timeval start, end; while (1) { int n; //cin >> n; n = 41; if (n < 0) break; gettimeofday(&start, 0); int res = fib(n); gettimeofday(&end, 0); int sec = end.tv_sec - start.tv_sec; int usec = end.tv_usec - start.tv_usec; cout << res << endl; cout << sec << " " << usec <<endl; break; } return 0; }

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