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• 1k of Program Space, 64 bytes of RAM. Is assembly an absolute must?

  - by Earlz

  (If your lazy see bottom for TL;DR) Hello, I am planning to build a new (prototype) project dealing with physical computing. Basically, I have wires. These wires all need to have their voltage read at the same time. More than a few hundred microseconds difference between the readings of each wire will completely screw it up. The Arduino takes about 114 microseconds. So the most I could read is 2 or 3 wires before the latency would skew the accuracy of the readings. So my plan is to have an Arduino as the "master" of an array of ATTinys. The arduino is pretty cramped for space, but it's a massive playground compared to the tinys. An ATTiny13A has 1k of flash ROM(program space), 64 bytes of RAM, and 64 bytes of (not-durable and slow) EEPROM. (I'm choosing this for price as well as size) The ATTinys in my system will not do much. Basically, all they will do is wait for a signal from the Master, and then read the voltage of 1 or 2 wires and store it in RAM(or possibly EEPROM if it's that cramped). And then send it to the Master using only 1 wire for data.(no room for more than that!). So far then, all I should have to do is implement trivial voltage reading code (using built in ADC). But this communication bit I'm worried about. Do you think a communication protocol(using just 1 wire!) could even be implemented in such constraints? TL;DR: In less than 1k of program space and 64 bytes of RAM(and 64 bytes of EEPROM) do you think it is possible to implement a 1 wire communication protocol? Would I need to drop to assembly to make it fit? I know that currently my Arduino programs linking to the Wiring library are over 8k, so I'm a bit concerned.

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• determining True/False.

  - by sil3nt

  Hi there, the following code #include <iostream> using namespace std; int main(){ char greeting[50] = "goodmorning everyone"; char *s1 = greeting; char *s2 = &greeting[7]; bool test = s2-s1; cout << "s1 is: " << s1 << endl; cout << "s2 is: " << s2 << endl; if (test == true ){ cout << "test is true and is: " << test << endl; } if (test == false){ cout<< "test is false and is: " << test << endl; } return 0; } outputs: s1 is: goodmorning everyone s2 is: ning everyone test is true and is: 1 here what does the line bool test = s2-s1; actually evaluate?, is it the length of the string?. If so, then seeing as s2 is a smaller than s1 it should be negative correct?, and yet the output is true?. Also if i change it to bool test = s1-s2; I still end up with the same result. So it doesnt matter whether its negative or positive the it will be true? and only false when 0?. what does the s2-s1 mean? -cheers (trying to get rid of doubts:))

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• sorting names in a linked list

  - by sil3nt

  Hi there, I'm trying to sort names into alphabetical order inside a linked list but am getting a run time error. what have I done wrong here? #include <iostream> #include <string> using namespace std; struct node{ string name; node *next; }; node *A; void addnode(node *&listpointer,string newname){ node *temp; temp = new node; if (listpointer == NULL){ temp->name = newname; temp->next = listpointer; listpointer = temp; }else{ node *add; add = new node; while (true){ if(listpointer->name > newname){ add->name = newname; add->next = listpointer->next; break; } listpointer = listpointer->next; } } } int main(){ A = NULL; string name1 = "bob"; string name2 = "tod"; string name3 = "thomas"; string name4 = "kate"; string name5 = "alex"; string name6 = "jimmy"; addnode(A,name1); addnode(A,name2); addnode(A,name3); addnode(A,name4); addnode(A,name5); addnode(A,name6); while(true){ if(A == NULL){break;} cout<< "name is: " << A->name << endl; A = A->next; } return 0; }

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• How to provide js-ctypes in a spidermonkey embedding?

  - by Triston J. Taylor

  Summary I have looked over the code the SpiderMonkey 'shell' application uses to create the ctypes JavaScript object, but I'm a less-than novice C programmer. Due to the varying levels of insanity emitted by modern build systems, I can't seem to track down the code or command that actually links a program with the desired functionality. method.madness This js-ctypes implementation by The Mozilla Devs is an awesome addition. Since its conception, scripting has been primarily used to exert control over more rigorous and robust applications. The advent of js-ctypes to the SpiderMonkey project, enables JavaScript to stand up and be counted as a full fledged object oriented rapid application development language flying high above 'the bar' set by various venerable application development languages such as Microsoft's VB6. Shall we begin? I built SpiderMonkey with this config: ./configure --enable-ctypes --with-system-nspr followed by successful execution of: make && make install The js shell works fine and a global ctypes javascript object was verified operational in that shell. Working with code taken from the first source listing at How to embed the JavaScript Engine -MDN, I made an attempt to instantiate the JavaScript ctypes object by inserting the following code at line 66: /* Populate the global object with the ctypes object. */ if (!JS_InitCTypesClass(cx, global)) return NULL; /* I compiled with: g++ $(./js-config --cflags --libs) hello.cpp -o hello It compiles with a few warnings: hello.cpp: In function ‘int main(int, const char**)’: hello.cpp:69:16: warning: converting to non-pointer type ‘int’ from NULL [-Wconversion-null] hello.cpp:80:20: warning: deprecated conversion from string constant to ‘char*’ [-Wwrite-strings] hello.cpp:89:17: warning: NULL used in arithmetic [-Wpointer-arith] But when you run the application: ./hello: symbol lookup error: ./hello: undefined symbol: JS_InitCTypesClass Moreover JS_InitCTypesClass is declared extern in 'dist/include/jsapi.h', but the function resides in 'ctypes/CTypes.cpp' which includes its own header 'CTypes.h' and is compiled at some point by some command during 'make' to yeild './CTypes.o'. As I stated earlier, I am less than a novice with the C code, and I really have no idea what to do here. Please give or give direction to a generic example of making the js-ctypes object functional in an embedding.

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• C/C++: Passing a structure by value, with another structure as one of its members, changes values of

  - by jellyfisharepretty

  Sorry for the confusing title, but it basically says it all. Here's the structures I'm using (found in OpenCV) : struct CV_EXPORTS CvRTParams : public CvDTreeParams { bool calc_var_importance; int nactive_vars; CvTermCriteria term_crit; CvRTParams() : CvDTreeParams( 5, 10, 0, false, 10, 0, false, false, 0 ), calc_var_importance(false), nactive_vars(0) { term_crit = cvTermCriteria( CV_TERMCRIT_ITER+CV_TERMCRIT_EPS, 50, 0.1 ); } } and typedef struct CvTermCriteria { int type; int max_iter; double epsilon; } CvTermCriteria; CV_INLINE CvTermCriteria cvTermCriteria( int type, int max_iter, double epsilon ) { CvTermCriteria t; t.type = type; t.max_iter = max_iter; t.epsilon = (float)epsilon; return t; } Now, I initialize a CvRTParams structure and set values for its members : CvRTParams params; params.max_depth = 8; params.min_sample_count = 10; params.regression_accuracy = 0; params.use_surrogates = false; params.max_categories = 10; params.priors = priors; params.calc_var_importance = true; params.nactive_vars = 9; params.term_crit.max_iter = 33; params.term_crit.epsilon = 0.1; params.term_crit.type = 3; Then call a function of an object, taking params in as a parameter : CvRTrees* rt = new CvRTrees; rt->train(t, CV_ROW_SAMPLE, r, 0, 0, var_type, 0, params) What happens now ? Values of... params.term_crit.max_iter params.term_crit.epsilon params.term_crit.type have changed ! They are no longer 33, 0.1 and 3, but something along the lines of 3, 7.05541e-313 and 4, and this, for the whole duration of the CvRtrees::train() function...

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• 1k of Program Space, 64 bytes of RAM. Is 1 wire communication possible?

  - by Earlz

  (If your lazy see bottom for TL;DR) Hello, I am planning to build a new (prototype) project dealing with physical computing. Basically, I have wires. These wires all need to have their voltage read at the same time. More than a few hundred microseconds difference between the readings of each wire will completely screw it up. The Arduino takes about 114 microseconds. So the most I could read is 2 or 3 wires before the latency would skew the accuracy of the readings. So my plan is to have an Arduino as the "master" of an array of ATTinys. The arduino is pretty cramped for space, but it's a massive playground compared to the tinys. An ATTiny13A has 1k of flash ROM(program space), 64 bytes of RAM, and 64 bytes of (not-durable and slow) EEPROM. (I'm choosing this for price as well as size) The ATTinys in my system will not do much. Basically, all they will do is wait for a signal from the Master, and then read the voltage of 1 or 2 wires and store it in RAM(or possibly EEPROM if it's that cramped). And then send it to the Master using only 1 wire for data.(no room for more than that!). So far then, all I should have to do is implement trivial voltage reading code (using built in ADC). But this communication bit I'm worried about. Do you think a communication protocol(using just 1 wire!) could even be implemented in such constraints? TL;DR: In less than 1k of program space and 64 bytes of RAM(and 64 bytes of EEPROM) do you think it is possible to implement a 1 wire communication protocol? Would I need to drop to assembly to make it fit? I know that currently my Arduino programs linking to the Wiring library are over 8k, so I'm a bit concerned.

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• left-hand operand of comma has no effect?

  - by sil3nt

  Hello there, I'm having some trouble with this warning message, it is implemented within a template container class int k = 0, l = 0; for ( k =(index+1), l=0; k < sizeC, l < (sizeC-index); k++,l++){ elements[k] = arryCpy[l]; } delete[] arryCpy; this is the warning i get cont.h: In member function `void Container<T>::insert(T, int)': cont.h:99: warning: left-hand operand of comma has no effect cont.h: In member function `void Container<T>::insert(T, int) [with T = double]': a5testing.cpp:21: instantiated from here cont.h:99: warning: left-hand operand of comma has no effect cont.h: In member function `void Container<T>::insert(T, int) [with T = std::string]': a5testing.cpp:28: instantiated from here cont.h:99: warning: left-hand operand of comma has no effect >Exit code: 0

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• Building elf within Eclipse

  - by BSchlinker

  Hey guys, I'm having trouble building an Elf file within Eclipse. It seems that everytime I build, a PE / portable executable for windows is created. I've gone into the Binary Parser section and checked Elf Parser while making sure that everything else is unchecked. However, I continue to end up with a PE which I cannot run on Linux. Any ideas? Thanks

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• Handling responses in libcurl

  - by sfactor

  i have a code to send a Form Post with login credentials to a webpage. it looks like this CURL *curl; CURLcode res; struct curl_httppost *formpost=NULL; struct curl_httppost *lastptr=NULL; struct curl_slist *headerlist=NULL; static const char buf[] = "Expect:"; curl_global_init(CURL_GLOBAL_ALL); /* Fill in the username */ curl_formadd(&formpost, &lastptr, CURLFORM_COPYNAME, "user", CURLFORM_COPYCONTENTS, "username", CURLFORM_END); /* Fill in the password */ curl_formadd(&formpost, &lastptr, CURLFORM_COPYNAME, "pass", CURLFORM_COPYCONTENTS, "password", CURLFORM_END); /* Fill in the submit field too, even if this is rarely needed */ curl_formadd(&formpost, &lastptr, CURLFORM_COPYNAME, "submit", CURLFORM_COPYCONTENTS, "send", CURLFORM_END); curl = curl_easy_init(); /* initalize custom header list (stating that Expect: 100-continue is not wanted */ headerlist = curl_slist_append(headerlist, buf); if(curl) { /* what URL that receives this POST */ curl_easy_setopt(curl, CURLOPT_URL, "http://127.0.0.1:8000/index.html"); /* only disable 100-continue header if explicitly requested */ curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headerlist); curl_easy_setopt(curl, CURLOPT_HTTPPOST, formpost); res = curl_easy_perform(curl); /* always cleanup */ curl_easy_cleanup(curl); /* then cleanup the formpost chain */ curl_formfree(formpost); /* free slist */ curl_slist_free_all (headerlist); } now i need to know is how do i handle the responses i get back from the server? i need to store the response into a string and then work on it.

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• Possible to use a .dll on Linux

  - by random_hero

  Question: Is it possible to compile a program on linux using a .dll file? Where this is going: This .dll will be used to write a php extension to some proprietary software from a third party. Background and Research: I have been given a library called proprietary.lib. I was curious, as I have never seen the .lib extension before, so I typed: file proprietary.lib The output was: proprietary.lib: current ar archive I did some research and found that ar is more-or-less tar (and in fact, I guess tar has since replaced ar in most *nix environments). Upon inspecting the ar manpage, I saw the t option, which displays a table listing of the contents of that archive. Cool. So I type: ar t proprietary.lib And get: proprietary.dll proprietary.dll ... (snip X lines) ...

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• How to include all objects of an archive in a shared object?

  - by Didier Trosset

  When compiling our project, we create several archives (static libraries), say liby.a and libz.a that each contains an object file defining a function y_function() and z_function(). Then, these archives are joined in a shared object, say libyz.so, that is one of our main distributable target. g++ -fPIC -c -o y.o y.cpp ar cr liby.a y.o g++ -fPIC -c -o z.o z.cpp ar cr libz.a z.o g++ -shared -L. -ly -lz -o libyz.so When using this shared object into the example program, say x.c, the link fails because of an undefined references to functions y_function() and z_function(). g++ x.o -L. -lyz -o xyz It works however when I link the final executable directly with the archives (static libraries). g++ x.o -L. -ly -lz -o xyz My guess is that the object files contained in the archives are not linked into the shared library because they are not used in it. How to force inclusion? Edit: Inclusion can be forced using --whole-archive ld option. But if results in compilation errors: g++ -shared '-Wl,--whole-archive' -L. -ly -lz -o libyz.so /usr/lib/libc_nonshared.a(elf-init.oS): In function `__libc_csu_init': (.text+0x1d): undefined reference to `__init_array_end' /usr/bin/ld: /usr/lib/libc_nonshared.a(elf-init.oS): relocation R_X86_64_PC32 against undefined hidden symbol `__init_array_end' can not be used when making a shared object /usr/bin/ld: final link failed: Bad value Any idea where this comes from?

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• Which format does static library (*.lib) files use? Where can I find "Official" specifications of *.

  - by claws

  Just now I found that static libraries in *nix systems, in other words *.a libraries are nothing but archives of relocatables(*.o files) in ar fromat. What about static libraries(*.lib files) in windows? Which format are they in? I found an article: http://www.microsoft.com/msj/0498/hood0498.aspx which explains *.lib file structure. But Where can I find "Official" specifications of *.lib file structure/format? Other than ar.exe of mingw is there any tool from Microsoft which extracts relocatable objects of *.lib & *.a files? EDIT: I wonder why I'm unable to get to this question. If there are no official specifications. Then how does the compiler ('linker' to be more correct) writers work with *.LIB files?

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• Linux: modpost does not build anything

  - by waffleman

  I am having problems getting any kernel modules to build on my machine. Whenever I build a module, modpost always says there are zero modules: MODPOST 0 modules To troubleshoot the problem, I wrote a test module (hello.c): #include <linux/module.h> /* Needed by all modules */ #include <linux/kernel.h> /* Needed for KERN_INFO */ #include <linux/init.h> /* Needed for the macros */ static int __init hello_start(void) { printk(KERN_INFO "Loading hello module...\n"); printk(KERN_INFO "Hello world\n"); return 0; } static void __exit hello_end(void) { printk(KERN_INFO "Goodbye Mr.\n"); } module_init(hello_start); module_exit(hello_end); Here is the Makefile for the module: obj-m = hello.o KVERSION = $(shell uname -r) all: make -C /lib/modules/$(KVERSION)/build M=$(shell pwd) modules clean: make -C /lib/modules/$(KVERSION)/build M=$(shell pwd) clean When I build it on my machine, I get the following output: make -C /lib/modules/2.6.32-27-generic/build M=/home/waffleman/tmp/mod-test modules make[1]: Entering directory `/usr/src/linux-headers-2.6.32-27-generic' CC [M] /home/waffleman/tmp/mod-test/hello.o Building modules, stage 2. MODPOST 0 modules make[1]: Leaving directory `/usr/src/linux-headers-2.6.32-27-generic' When I make the module on another machine, it is successful: make -C /lib/modules/2.6.24-27-generic/build M=/home/somedude/tmp/mod-test modules make[1]: Entering directory `/usr/src/linux-headers-2.6.24-27-generic' CC [M] /home/somedude/tmp/mod-test/hello.o Building modules, stage 2. MODPOST 1 modules CC /home/somedude/tmp/mod-test/hello.mod.o LD [M] /home/somedude/tmp/mod-test/hello.ko make[1]: Leaving directory `/usr/src/linux-headers-2.6.24-27-generic' I looked for any relevant documentation about modpost, but found little. Anyone know how modpost decides what to build? Is there an environment that I am possibly missing? BTW here is what I am running: uname -a Linux waffleman-desktop 2.6.32-27-generic #49-Ubuntu SMP Wed Dec 1 23:52:12 UTC 2010 i686 GNU/Linux

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• write system call to file desciptor ZERO

  - by shadyabhi

  int main ( ) { char C[] = "Hello World"; write(0,C,sizeof(C)); return 0; } In the above program, I am writing to File descriptor ZERO which I suppose by default is STDIN.. Then why I am I getting output at STDOUT? shadyabhi@shadyabhi-desktop:~$ ./a.out Hello Worldshadyabhi@shadyabhi-desktop:~$

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• Which free C compiler gives options for greater optimizations?

  - by Naga

  Can you please give me some comparison between C compilers especially with respect to optimization?

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• how does fgets internally works?

  - by Registered User

  Well it is a basic question but I seem confused enough. #include<stdio.h> int main() { char a[100]; printf("Enter a string\n"); scanf("%s",a); } Basically the above is what I want to achieve. If I enter a string James Bond then I want that to be stored in array a. But the problem is because of presence of a blank space in between only James word is stored. So how can I solve this one. UPDATE After the replies given below I understand fgets() would be a better choice. I want to know internal working of fgets as why is it able to store the string with space where as scanf is not able to do the same.

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• Suppress Xcode warning? 'weak_import' attribute ignored

  - by MT

  Hi, I've got quite a large Xcode project that since an Xcode upgrade is giving me loads of "'weak_import' attribute ignored" warnings, they are coming from WebKit, and a bit of research suggests it's a compiler bug. Is there anyway to suppress them, I'm getting thousands, making the 'real' warnings impossible to find. Cheers MT

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• C inline assembly of x96 fbstp instruction

  - by David HUnter

  Was wondering how to inline a usage of fbstp on a 32 bit I86 architecture. I tried something like int main( ) { double foo = 100.0; long bar = 0; asm( "pushl %1; fbstp %0" : "=m"(bar) : "r"(foo) ); ... But bar is unchanged. I have tried reading everything I can find on this but most example simply do things like add two integers together. I can’t find any that talk about pushing operands onto the stack and what I should be doing when an instruction like fbstp writes 80 bits of data back to memory ( i.e. what C type to use ) and how to specify it in the asm syntax. Also on x86-64 there seems to be a pushq and no pushl but fbstp still exists whereas fbstq does not. Is there some other magic for 64 bit.

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• gcov line count is different from no of lines in source code

  - by sarath

  output of gcov says no of lines executed 70 % of 10 but my code has more than 10 lines.. it does not count braces , else statement please help ..

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• destructor and copy-constructor calling..(why does it get called at these times)

  - by sil3nt

  Hello there, I have the following code #include <iostream> using namespace std; class Object { public: Object(int id){ cout << "Construct(" << id << ")" << endl; m_id = id; } Object(const Object& obj){ cout << "Copy-construct(" << obj.m_id << ")" << endl; m_id = obj.m_id; } Object& operator=(const Object& obj){ cout << m_id << " = " << obj.m_id << endl; m_id = obj.m_id; return *this; } ~Object(){ cout << "Destruct(" << m_id << ")" << endl; } private: int m_id; }; Object func(Object var) { return var; } int main(){ Object v1(1); cout << "( a )" << endl; Object v2(2); v2 = v1; cout << "( b )" << endl; Object v4 = v1; Object *pv5; pv5 = &v1; pv5 = new Object(5); cout << "( c )" << endl; func(v1); cout << "( d )" << endl; delete pv5; } which outputs Construct(1) ( a ) Construct(2) 2 = 1 ( b ) Copy-construct(1) Construct(5) ( c ) Copy-construct(1) Copy-construct(1) Destruct(1) Destruct(1) ( d ) Destruct(5) Destruct(1) Destruct(1) Destruct(1) I have some issues with this, firstly why does Object v4 = v1; call the copy constructor and produce Copy-construct(1) after the printing of ( b ). Also after the printing of ( c ) the copy-constructor is again called twice?, Im not certain of how this function works to produce that Object func(Object var) { return var; } and just after that Destruct(1) gets called twice before ( d ) is printed. sorry for the long question, I'm confused with the above.

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• "Ambiguous template specialization" problem

  - by Setien

  I'm currently porting a heap of code that has previously only been compiled with Visual Studio 2008. In this code, there's an arrangement like this: template <typename T> T convert( const char * s ) { // slow catch-all std::istringstream is( s ); T ret; is >> ret; return ret; } template <> inline int convert<int>( const char * s ) { return (int)atoi( s ); } Generally, there are a lot of specializations of the templated function with different return types that are invoked like this: int i = convert<int>( szInt ); The problem is, that these template specializations result in "Ambiguous template specialization". If it was something besides the return type that differentiated these function specializations, I could obviously just use overloads, but that's not an option. How do I solve this without having to change all the places the convert functions are called?

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• Undefined reference to vtable

  - by RyanG

  So, I'm getting the infamously horrible "undefined reference to 'vtable..." error for the following code (The class in question is CGameModule.) and I cannot for the life of me understand what the problem is. At first, I thought it was related to forgetting to give a virtual function a body, but as far as I understand, everything is all here. The inheritance chain is a little long, but here is the related source code. I'm not sure what other information I should provide. My code: class CGameModule : public CDasherModule { public: CGameModule(Dasher::CEventHandler *pEventHandler, CSettingsStore *pSettingsStore, CDasherInterfaceBase *pInterface, ModuleID_t iID, const char *szName) : CDasherModule(pEventHandler, pSettingsStore, iID, 0, szName) { g_pLogger->Log("Inside game module constructor"); m_pInterface = pInterface; } virtual ~CGameModule() {}; std::string GetTypedTarget(); std::string GetUntypedTarget(); bool DecorateView(CDasherView *pView) { //g_pLogger->Log("Decorating the view"); return false; } void SetDasherModel(CDasherModel *pModel) { m_pModel = pModel; } virtual void HandleEvent(Dasher::CEvent *pEvent); private: CDasherNode *pLastTypedNode; CDasherNode *pNextTargetNode; std::string m_sTargetString; size_t m_stCurrentStringPos; CDasherModel *m_pModel; CDasherInterfaceBase *m_pInterface; }; } Inherits from... class CDasherModule; typedef std::vector<CDasherModule*>::size_type ModuleID_t; /// \ingroup Core /// @{ class CDasherModule : public Dasher::CDasherComponent { public: CDasherModule(Dasher::CEventHandler * pEventHandler, CSettingsStore * pSettingsStore, ModuleID_t iID, int iType, const char *szName); virtual ModuleID_t GetID(); virtual void SetID(ModuleID_t); virtual int GetType(); virtual const char *GetName(); virtual bool GetSettings(SModuleSettings **pSettings, int *iCount) { return false; }; private: ModuleID_t m_iID; int m_iType; const char *m_szName; }; Which inherits from.... namespace Dasher { class CEvent; class CEventHandler; class CDasherComponent; }; /// \ingroup Core /// @{ class Dasher::CDasherComponent { public: CDasherComponent(Dasher::CEventHandler* pEventHandler, CSettingsStore* pSettingsStore); virtual ~CDasherComponent(); void InsertEvent(Dasher::CEvent * pEvent); virtual void HandleEvent(Dasher::CEvent * pEvent) {}; bool GetBoolParameter(int iParameter) const; void SetBoolParameter(int iParameter, bool bValue) const; long GetLongParameter(int iParameter) const; void SetLongParameter(int iParameter, long lValue) const; std::string GetStringParameter(int iParameter) const; void SetStringParameter(int iParameter, const std::string & sValue) const; ParameterType GetParameterType(int iParameter) const; std::string GetParameterName(int iParameter) const; protected: Dasher::CEventHandler *m_pEventHandler; CSettingsStore *m_pSettingsStore; }; /// @} #endif

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• base destructor called twice after derived object?

  - by sil3nt

  hey there, why is the base destructor called twice at the end of this program? #include <iostream> using namespace std; class B{ public: B(){ cout << "BC" << endl; x = 0; } virtual ~B(){ cout << "BD" << endl; } void f(){ cout << "BF" << endl; } virtual void g(){ cout << "BG" << endl; } private: int x; }; class D: public B{ public: D(){ cout << "dc" << endl; y = 0; } virtual ~D(){ cout << "dd" << endl; } void f(){ cout << "df" << endl; } virtual void g(){ cout << "dg" << endl; } private: int y; }; int main(){ B b, * bp = &b; D d, * dp = &d; bp->f(); bp->g(); bp = dp; bp->f(); bp->g(); }

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• C++ preprocessing error in the code

  - by mkal

  #include "iostream" #include "string" using namespace std; #define AA(bb) \ string(::##bb); int main (int argc, char *argv[]) { AA(aa); } This gives me a bunch of errors but I am trying to understand this error pre.cpp:11:1: error: pasting "::" and "aa" does not give a valid preprocessing token Any ideas?

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• Using libgrib2c in c++ application, linker error "Undefined reference to..."

  - by Rich

  EDIT: If you're going to be doing things with GRIB files I would recommend the GDAL library which is backed by the Open Source Geospatial Foundation. You will save yourself a lot of headache :) I'm using Qt creator in Ubuntu creating a c++ app. I am attempting to use an external lib, libgrib2c.a, that has a header grib2.h. Everything compiles, but when it tries to link I get the error: undefined reference to 'seekgb(_IO_FILE*, long, long, long*, long*) I have tried wrapping the header file with: extern "C"{ #include "grib2.h" } But it didn't fix anything so I figured that was not my problem. In the .pro file I have the line: include($${ROOT}/Shared/common/commonLibs.pri) and in commonLibs.pri I have: INCLUDEPATH+=$${ROOT}/external_libs/g2clib/include LIBS+=-L$${ROOT}/external_libs/g2clib/lib LIBS+=-lgrib2c I am not encountering an error finding the library. If I do a nm command on the libgrib2c.a I get: nm libgrib2c.a | grep seekgb seekgb.o: 00000000 T seekgb And when I run qmake with the additional argument of LIBS+=-Wl,--verbose I can find the lib file in the output: attempt to open /usr/lib/libgrib2c.so failed attempt to open /usr/lib/libgrib2c.a failed attempt to open /mnt/sdb1/ESMF/App/ESMF_App/../external_libs/linux/qwt_6.0.2/lib/libgrib2c.so failed attempt to open /mnt/sdb1/ESMF/App/ESMF_App/../external_libs/linux/qwt_6.0.2/lib/libgrib2c.a failed attempt to open ..//Shared/Config/lib/libgrib2c.so failed attempt to open ..//Shared/Config/lib/libgrib2c.a failed attempt to open ..//external_libs/libssh2/lib/libgrib2c.so failed attempt to open ..//external_libs/libssh2/lib/libgrib2c.a failed attempt to open ..//external_libs/openssl/lib/libgrib2c.so failed attempt to open ..//external_libs/openssl/lib/libgrib2c.a failed attempt to open ..//external_libs/g2clib/lib/libgrib2c.so failed attempt to open ..//external_libs/g2clib/lib/libgrib2c.a succeeded Although it doesn't show any of the .o files in the library is this because it is a c library in my c++ app? in the .cpp file that I am trying to use the library I have: #include "gribreader.h" #include <stdio.h> #include <stdlib.h> #include <external_libs/g2clib/include/grib2.h> #include <Shared/logging/Logger.hpp> //------------------------------------------------------------------------------ /// Opens a GRIB file from disk. /// /// This function opens the grib file and searches through it for how many GRIB /// messages are contained as well as their starting locations. /// /// \param a_filePath. The path to the file to be opened. /// \return True if successful, false if not. //------------------------------------------------------------------------------ bool GRIBReader::OpenGRIB(std::string a_filePath) { LOG(notification)<<"Attempting to open grib file: "<< a_filePath; if(isOpen()) { CloseGRIB(); } m_filePath = a_filePath; m_filePtr = fopen(a_filePath.c_str(), "r"); if(m_filePtr == NULL) { LOG(error)<<"Unable to open file: " << a_filePath; return false; } LOG(notification)<<"Successfully opened GRIB file"; g2int currentMessageSize(1); g2int seekPosition(0); g2int lengthToBeginningOfGrib(0); g2int seekLength(32000); int i(0); int iterationLimit(300); m_GRIBMessageLocations.clear(); m_GRIBMessageSizes.clear(); while(i < iterationLimit) { seekgb(m_filePtr, seekPosition, seekLength, &lengthToBeginningOfGrib, &currentMessageSize); if(currentMessageSize != 0) { LOG(verbose) << "Adding GRIB message location " << lengthToBeginningOfGrib << " with length " << currentMessageSize; m_GRIBMessageLocations.push_back(lengthToBeginningOfGrib); m_GRIBMessageSizes.push_back(currentMessageSize); seekPosition = lengthToBeginningOfGrib + currentMessageSize; LOG(verbose) << "GRIB seek position moved to " << seekPosition; } else { LOG(notification)<<"End of GRIB file found, after "<< i << " GRIB messages."; break; } } if(i >= iterationLimit) { LOG(warning) << "The iteration limit of " << iterationLimit << "was reached while searching for GRIB messages"; } return true; } And the header grib2.h is as follows: #ifndef _grib2_H #define _grib2_H #include<stdio.h> #define G2_VERSION "g2clib-1.4.0" #ifdef __64BIT__ typedef int g2int; typedef unsigned int g2intu; #else typedef long g2int; typedef unsigned long g2intu; #endif typedef float g2float; struct gtemplate { g2int type; /* 3=Grid Defintion Template. */ /* 4=Product Defintion Template. */ /* 5=Data Representation Template. */ g2int num; /* template number. */ g2int maplen; /* number of entries in the static part */ /* of the template. */ g2int *map; /* num of octets of each entry in the */ /* static part of the template. */ g2int needext; /* indicates whether or not the template needs */ /* to be extended. */ g2int extlen; /* number of entries in the template extension. */ g2int *ext; /* num of octets of each entry in the extension */ /* part of the template. */ }; typedef struct gtemplate gtemplate; struct gribfield { g2int version,discipline; g2int *idsect; g2int idsectlen; unsigned char *local; g2int locallen; g2int ifldnum; g2int griddef,ngrdpts; g2int numoct_opt,interp_opt,num_opt; g2int *list_opt; g2int igdtnum,igdtlen; g2int *igdtmpl; g2int ipdtnum,ipdtlen; g2int *ipdtmpl; g2int num_coord; g2float *coord_list; g2int ndpts,idrtnum,idrtlen; g2int *idrtmpl; g2int unpacked; g2int expanded; g2int ibmap; g2int *bmap; g2float *fld; }; typedef struct gribfield gribfield; /* Prototypes for unpacking API */ void seekgb(FILE *,g2int ,g2int ,g2int *,g2int *); g2int g2_info(unsigned char *,g2int *,g2int *,g2int *,g2int *); g2int g2_getfld(unsigned char *,g2int ,g2int ,g2int ,gribfield **); void g2_free(gribfield *); /* Prototypes for packing API */ g2int g2_create(unsigned char *,g2int *,g2int *); g2int g2_addlocal(unsigned char *,unsigned char *,g2int ); g2int g2_addgrid(unsigned char *,g2int *,g2int *,g2int *,g2int ); g2int g2_addfield(unsigned char *,g2int ,g2int *, g2float *,g2int ,g2int ,g2int *, g2float *,g2int ,g2int ,g2int *); g2int g2_gribend(unsigned char *); /* Prototypes for supporting routines */ extern double int_power(double, g2int ); extern void mkieee(g2float *,g2int *,g2int); void rdieee(g2int *,g2float *,g2int ); extern gtemplate *getpdstemplate(g2int); extern gtemplate *extpdstemplate(g2int,g2int *); extern gtemplate *getdrstemplate(g2int); extern gtemplate *extdrstemplate(g2int,g2int *); extern gtemplate *getgridtemplate(g2int); extern gtemplate *extgridtemplate(g2int,g2int *); extern void simpack(g2float *,g2int,g2int *,unsigned char *,g2int *); extern void compack(g2float *,g2int,g2int,g2int *,unsigned char *,g2int *); void misspack(g2float *,g2int ,g2int ,g2int *, unsigned char *, g2int *); void gbit(unsigned char *,g2int *,g2int ,g2int ); void sbit(unsigned char *,g2int *,g2int ,g2int ); void gbits(unsigned char *,g2int *,g2int ,g2int ,g2int ,g2int ); void sbits(unsigned char *,g2int *,g2int ,g2int ,g2int ,g2int ); int pack_gp(g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *, g2int *); #endif /* _grib2_H */ I have been scratching my head for two days on this. If anyone has an idea on what to do or can point me in some sort of direction, I'm stumped. Also, if you have any comments on how I can improve this post I'd love to hear them, kinda new at this posting thing. Usually I'm able to find an answer in the vast stores of knowledge already contained on the web.

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