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  • c - strncpy issue

    - by Joe
    Hi there, I am getting segmentation fault when using strncpy and (pointer-to-struct)-(member) notation: I have simplified my code. I initialise a struct and set all of it's tokens to an empty string. Then a declare a pointer to a struct and assign the address of the struct to it. I pass the pointer to a function. I can print out the contents of the struct at the beginning of the function, but if I try to use the tp - mnemonic in a strncpy function, I get seg fault. Can anyone tell me what I am doing wrong? typedef struct tok { char* label; char* mnem; char* operand; }Tokens; Tokens* tokenise(Tokens* tp, char* line) { // This prints fine printf("Print this - %s\n", tp -> mnem); // This function gives me segmentation fault strncpy(tp -> mnem, line, 4); return tp; } int main() { char* line = "This is a line"; Tokens tokens; tokens.label = ""; tokens.mnem = "load"; tokens.operand = ""; Tokens* tp = &tokens; tp = tokenise(tp, line); return 0; } I have used printf statements to confirm that the code definitely stops executing at the strncpy function. Can anyone tell me where I am going wrong? Many thanks Joe

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  • when to use strncpy or memmove

    - by robUK
    Hello, gcc 4.4.4 c89 I have always used strncpy to copy strings. I have never really used memmove or memcpy very much. However, I am just wondering when would you decide whether to use strncpy, memmove, or memcpy? The code I am writing is for a client/server application. In the documentation they use bcopy. However, could I do the same with the others? bcopy((char*)server->h_addr, (char*)&serv_addr.sin_addr.s_addr, server->h_length); Many thanks,

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  • what's wrong with my one-liner strncpy: while(*s++ = *t++ && n-- > 0);?

    - by pvd
    #include <stdio.h> #define STR_BUF 10000 #define STR_MATCH 7 void mystrncpy(char* s, char* t, int n) { while(*s++ = *t++ && n-- > 0); } int main() { int result; char str_s[STR_BUF] = "not so long test string"; char buf_1[STR_BUF]; mystrncpy(buf_1, str_s, STR_MATCH); printf ("buf_1 (mystrncpy, 7 chars): %s\n", buf_1); return 0; } When I run it, nothing happened ian@ubuntu:~/tmp$ gcc myncpy.c -o myn&&./myn buf_1 (mystrncpy, 7chars):

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  • Which functions in the C standard library commonly encourage bad practice?

    - by Ninefingers
    Hello all, This is inspired by this question and the comments on one particular answer in that I learnt that strncpy is not a very safe string handling function in C and that it pads zeros, until it reaches n, something I was unaware of. Specifically, to quote R.. strncpy does not null-terminate, and does null-pad the whole remainder of the destination buffer, which is a huge waste of time. You can work around the former by adding your own null padding, but not the latter. It was never intended for use as a "safe string handling" function, but for working with fixed-size fields in Unix directory tables and database files. snprintf(dest, n, "%s", src) is the only correct "safe strcpy" in standard C, but it's likely to be a lot slower. By the way, truncation in itself can be a major bug and in some cases might lead to privilege elevation or DoS, so throwing "safe" string functions that truncate their output at a problem is not a way to make it "safe" or "secure". Instead, you should ensure that the destination buffer is the right size and simply use strcpy (or better yet, memcpy if you already know the source string length). And from Jonathan Leffler Note that strncat() is even more confusing in its interface than strncpy() - what exactly is that length argument, again? It isn't what you'd expect based on what you supply strncpy() etc - so it is more error prone even than strncpy(). For copying strings around, I'm increasingly of the opinion that there is a strong argument that you only need memmove() because you always know all the sizes ahead of time and make sure there's enough space ahead of time. Use memmove() in preference to any of strcpy(), strcat(), strncpy(), strncat(), memcpy(). So, I'm clearly a little rusty on the C standard library. Therefore, I'd like to pose the question: What C standard library functions are used inappropriately/in ways that may cause/lead to security problems/code defects/inefficiencies? In the interests of objectivity, I have a number of criteria for an answer: Please, if you can, cite design reasons behind the function in question i.e. its intended purpose. Please highlight the misuse to which the code is currently put. Please state why that misuse may lead towards a problem. I know that should be obvious but it prevents soft answers. Please avoid: Debates over naming conventions of functions (except where this unequivocably causes confusion). "I prefer x over y" - preference is ok, we all have them but I'm interested in actual unexpected side effects and how to guard against them. As this is likely to be considered subjective and has no definite answer I'm flagging for community wiki straight away. I am also working as per C99.

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  • Question about unions and heap allocated memory

    - by Dennis Miller
    I was trying to use a union to so I could update the fields in one thread and then read allfields in another thread. In the actual system, I have mutexes to make sure everything is safe. The problem is with fieldB, before I had to change it fieldB was declared like field A and C. However, due to a third party driver, fieldB must be alligned with page boundary. When I changed field B to be allocated with valloc, I run into problems. Questions: 1) Is there a way to statically declare fieldB alligned on page boundary. Basically do the same thing as valloc, but on the stack? 2) Is it possible to do a union when field B, or any field is being allocated on the heap?. Not sure if that is even legal. Here's a simple Test program I was experimenting with. This doesn't work unless you declare fieldB like field A and C, and make the obvious changes in the public methods. #include <iostream> #include <stdlib.h> #include <string.h> #include <stdio.h> class Test { public: Test(void) { // field B must be alligned to page boundary // Is there a way to do this on the stack??? this->field.fieldB = (unsigned char*) valloc(10); }; //I know this is bad, this class is being treated like //a global structure. Its self contained in another class. unsigned char* PointerToFieldA(void) { return &this->field.fieldA[0]; } unsigned char* PointerToFieldB(void) { return this->field.fieldB; } unsigned char* PointerToFieldC(void) { return &this->field.fieldC[0]; } unsigned char* PointerToAllFields(void) { return &this->allFields[0]; } private: // Is this union possible with field B being // allocated on the heap? union { struct { unsigned char fieldA[10]; //This field has to be alligned to page boundary //Is there way to be declared on the stack unsigned char* fieldB; unsigned char fieldC[10]; } field; unsigned char allFields[30]; }; }; int main() { Test test; strncpy((char*) test.PointerToFieldA(), "0123456789", 10); strncpy((char*) test.PointerToFieldB(), "1234567890", 10); strncpy((char*) test.PointerToFieldC(), "2345678901", 10); char dummy[11]; dummy[10] = '\0'; strncpy(dummy, (char*) test.PointerToFieldA(), 10); printf("%s\n", dummy); strncpy(dummy, (char*) test.PointerToFieldB(), 10); printf("%s\n", dummy); strncpy(dummy, (char*) test.PointerToFieldC(), 10); printf("%s\n", dummy); char allFields[31]; allFields[30] = '\0'; strncpy(allFields, (char*) test.PointerToAllFields(), 30); printf("%s\n", allFields); return 0; }

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  • LSP packet modify

    - by kellogs
    Hello, anybody care to share some insights on how to use LSP for packet modifying ? I am using the non IFS subtype and I can see how (pseudo?) packets first enter WSPRecv. But how do I modify them ? My inquiry is about one single HTTP response that causes WSPRecv to be called 3 times :((. I need to modify several parts of this response, but since it comes in 3 slices, it is pretty hard to modify it accordingly. And, maybe on other machines or under different conditions (such as high traffic) there would only be one sole WSPRecv call, or maybe 10 calls. What is the best way to work arround this (please no NDIS :D), and how to properly change the buffer (lpBuffers-buf) by increasing it ? int WSPAPI WSPRecv( SOCKET s, LPWSABUF lpBuffers, DWORD dwBufferCount, LPDWORD lpNumberOfBytesRecvd, LPDWORD lpFlags, LPWSAOVERLAPPED lpOverlapped, LPWSAOVERLAPPED_COMPLETION_ROUTINE lpCompletionRoutine, LPWSATHREADID lpThreadId, LPINT lpErrno ) { LPWSAOVERLAPPEDPLUS ProviderOverlapped = NULL; SOCK_INFO *SocketContext = NULL; int ret = SOCKET_ERROR; *lpErrno = NO_ERROR; // // Find our provider socket corresponding to this one // SocketContext = FindAndRefSocketContext(s, lpErrno); if ( NULL == SocketContext ) { dbgprint( "WSPRecv: FindAndRefSocketContext failed!" ); goto cleanup; } // // Check for overlapped I/O // if ( NULL != lpOverlapped ) { /*bla bla .. not interesting in my case*/ } else { ASSERT( SocketContext->Provider->NextProcTable.lpWSPRecv ); SetBlockingProvider(SocketContext->Provider); ret = SocketContext->Provider->NextProcTable.lpWSPRecv( SocketContext->ProviderSocket, lpBuffers, dwBufferCount, lpNumberOfBytesRecvd, lpFlags, lpOverlapped, lpCompletionRoutine, lpThreadId, lpErrno); SetBlockingProvider(NULL); //is this the place to modify packet length and contents ? if (strstr(lpBuffers->buf, "var mapObj = null;")) { int nLen = strlen(lpBuffers->buf) + 200; /*CHAR *szNewBuf = new CHAR[]; CHAR *pIndex; pIndex = strstr(lpBuffers->buf, "var mapObj = null;"); nLen = strlen(strncpy(szNewBuf, lpBuffers->buf, (pIndex - lpBuffers->buf) * sizeof (CHAR))); nLen = strlen(strncpy(szNewBuf + nLen * sizeof(CHAR), "var com = null;\r\n", 17 * sizeof(CHAR))); pIndex += 18 * sizeof(CHAR); nLen = strlen(strncpy(szNewBuf + nLen * sizeof(CHAR), pIndex, 1330 * sizeof (CHAR))); nLen = strlen(strncpy(szNewBuf + nLen * sizeof(CHAR), "if (com == null)\r\n" \ "com = new ActiveXObject(\"InterCommJS.Gateway\");\r\n" \ "com.lat = latitude;\r\n" \ "com.lon = longitude;\r\n}", 111 * sizeof (CHAR))); pIndex = strstr(szNewBuf, "Content-Length:"); pIndex += 16 * sizeof(CHAR); strncpy(pIndex, "1465", 4 * sizeof(CHAR)); lpBuffers->buf = szNewBuf; lpBuffers->len += 128;*/ } if ( SOCKET_ERROR != ret ) { SocketContext->BytesRecv += *lpNumberOfBytesRecvd; } } cleanup: if ( NULL != SocketContext ) DerefSocketContext( SocketContext, lpErrno ); return ret; } Thank you

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  • Unable to build my c++ code with g++ 4.6.3

    - by Mriganka
    I am facing multiple issues with building my c++ code on Ubuntu 12.04. This code was building and running fine on RH Enterprise. I am using g++ 4.6.3. Here's the output of g++ -v. g++ -v Using built-in specs. COLLECT_GCC=g++ COLLECT_LTO_WRAPPER=/usr/lib/gcc/i686-linux-gnu/4.6/lto-wrapper Target: i686-linux-gnu Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro 4.6.3-1ubuntu5' --with-bugurl=file:///usr/share/doc/gcc-4.6/README.Bugs --enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.6 --enable-shared --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.6 --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-gnu-unique-object --enable-plugin --enable-objc-gc --enable-targets=all --disable-werror --with-arch-32=i686 --with-tune=generic --enable-checking=release --build=i686-linux-gnu --host=i686-linux-gnu --target=i686-linux-gnu Thread model: posix gcc version 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5) Here's a sample of my code: #include "Word.h" #include < string> using namespace std; pthread_mutex_t Word::_lock = PTHREAD_MUTEX_INITIALIZER; Word::Word(): _occurrences(1) { memset(_buf, 0, 25); } Word::Word(char *str): _occurrences(1) { memset(_buf, 0, 25); if (str != NULL) { strncpy(_buf, str, strlen(str)); } } g++ -c -ansi or g++ -c -std=c++98 or g++ -c -std=c++03, none of these options are able to build the code correctly. I get the following compilation errors: mriganka@ubuntu:~/WordCount$ make g++ -c -g -ansi Word.cpp -o Word.o Word.cpp: In constructor ‘Word::Word()’: Word.cpp:10:21: error: ‘memset’ was not declared in this scope Word.cpp: In constructor ‘Word::Word(char*)’: Word.cpp:16:21: error: ‘memset’ was not declared in this scope Word.cpp:19:34: error: ‘strlen’ was not declared in this scope Word.cpp:19:35: error: ‘strncpy’ was not declared in this scope Word.cpp: In member function ‘void Word::operator=(const Word&)’: Word.cpp:37:42: error: ‘strlen’ was not declared in this scope Word.cpp:37:43: error: ‘strncpy’ was not declared in this scope Word.cpp: In copy constructor ‘Word::Word(const Word&)’: Word.cpp:44:21: error: ‘memset’ was not declared in this scope Word.cpp:45:52: error: ‘strlen’ was not declared in this scope Word.cpp:45:53: error: ‘strncpy’ was not declared in this scope So basically g++ 4.6.3 on Ubuntu 12.04 is not able to recognize the standard c++ headers. And I am not finding a way out of this situation. Second problem: In order to make progress, I included < string.h instead of < string. But now I am facing linking errors with my message queue and pthread library functions. Here's the error that I am getting: mriganka@ubuntu:~/WordCount$ make g++ -c -g -ansi Word.cpp -o Word.o g++ -lrt -I/usr/lib/i386-linux-gnu Word.o HashMap.o main.o -o word_count main.o: In function `main': /home/mriganka/WordCount/main.cpp:75: undefined reference to `pthread_create' /home/mriganka/WordCount/main.cpp:90: undefined reference to `mq_open' /home/mriganka/WordCount/main.cpp:93: undefined reference to `mq_getattr' /home/mriganka/WordCount/main.cpp:113: undefined reference to `mq_send' /home/mriganka/WordCount/main.cpp:123: undefined reference to `pthread_join' /home/mriganka/WordCount/main.cpp:129: undefined reference to `mq_close' /home/mriganka/WordCount/main.cpp:130: undefined reference to `mq_unlink' main.o: In function `count_words(void*)': /home/mriganka/WordCount/main.cpp:151: undefined reference to `mq_open' /home/mriganka/WordCount/main.cpp:154: undefined reference to `mq_getattr' /home/mriganka/WordCount/main.cpp:162: undefined reference to `mq_timedreceive' collect2: ld returned 1 exit status Here's my makefile: CC=g++ CFLAGS=-c -g -ansi LDFLAGS=-lrt INC=-I/usr/lib/i386-linux-gnu SOURCES=Word.cpp HashMap.cpp main.cpp OBJECTS=$(SOURCES:.cpp=.o) EXECUTABLE=word_count all: $(SOURCES) $(EXECUTABLE) $(EXECUTABLE): $(OBJECTS) $(CC) $(LDFLAGS) $(INC) -pthread $(OBJECTS) -o $@ .cpp.o: $(CC) $(CFLAGS) $< -o $@ clean: rm -f *.o word_count Please help me to resolve both the issues. I searched online relentlessly for any solution of these problems, but no one seems to have encountered these issues.

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  • reading a line, tokenizing and assigning to struct in C

    - by Dervin Thunk
    line is fgets'd, and running in a while loop with counter n, d is a struct with 2 char arrays, p and q. Basically, in a few words, I want to read a line, separate it into 2 strings, one up until the first space, and the rest of the line. I clean up afterwards (\n from the file becomes \'0'). The code works, but is there a more idiomatic way to do this? What errors am I running into "unknowingly"? int spc = strcspn(line," "); strncpy(d[n].p, line, spc); d[n].p[spc+1]='\0'; int l = strlen(line)-spc; strncpy(d[n].q, line+spc+1, l); char* nl = strchr(d[n].q, '\n'); if(nl){ *nl='\0'; } n++; Thanks.

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  • Incompatible format types

    - by nebffa
    I'm playing around with strncpy in C and am having some trouble. The code is as follows: #include <stdio.h> #include <string.h> int main(int argc, char *argv[]) { char src[] = "Benjamin Franklin"; char dest[5]; strncpy(src, dest, sizeof(dest) / sizeof(char)); dest[5] = '\0'; printf("%s\n", dest); return 0; } which compiles with no errors using: gcc -Wall -g -Werror test.c -o test and prints out gibberish like p4?? I cannot really understand what I'm doing wrong especially since I have played around with it a lot and been looking online for answers. Perhaps since I am using arrays I am passing the address to printf without realising it?

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  • Optimizing sorting container of objects with heap-allocated buffers - how to avoid hard-copying buff

    - by Kache4
    I was making sure I knew how to do the op= and copy constructor correctly in order to sort() properly, so I wrote up a test case. After getting it to work, I realized that the op= was hard-copying all the data_. I figure if I wanted to sort a container with this structure (its elements have heap allocated char buffer arrays), it'd be faster to just swap the pointers around. Is there a way to do that? Would I have to write my own sort/swap function? #include <deque> //#include <string> //#include <utility> //#include <cstdlib> #include <cstring> #include <iostream> //#include <algorithm> // I use sort(), so why does this still compile when commented out? #include <boost/filesystem.hpp> #include <boost/foreach.hpp> using namespace std; namespace fs = boost::filesystem; class Page { public: // constructor Page(const char* path, const char* data, int size) : path_(fs::path(path)), size_(size), data_(new char[size]) { // cout << "Creating Page..." << endl; strncpy(data_, data, size); // cout << "done creating Page..." << endl; } // copy constructor Page(const Page& other) : path_(fs::path(other.path())), size_(other.size()), data_(new char[other.size()]) { // cout << "Copying Page..." << endl; strncpy(data_, other.data(), size_); // cout << "done copying Page..." << endl; } // destructor ~Page() { delete[] data_; } // accessors const fs::path& path() const { return path_; } const char* data() const { return data_; } int size() const { return size_; } // operators Page& operator = (const Page& other) { if (this == &other) return *this; char* newImage = new char[other.size()]; strncpy(newImage, other.data(), other.size()); delete[] data_; data_ = newImage; path_ = fs::path(other.path()); size_ = other.size(); return *this; } bool operator < (const Page& other) const { return path_ < other.path(); } private: fs::path path_; int size_; char* data_; }; class Book { public: Book(const char* path) : path_(fs::path(path)) { cout << "Creating Book..." << endl; cout << "pushing back #1" << endl; pages_.push_back(Page("image1.jpg", "firstImageData", 14)); cout << "pushing back #3" << endl; pages_.push_back(Page("image3.jpg", "thirdImageData", 14)); cout << "pushing back #2" << endl; pages_.push_back(Page("image2.jpg", "secondImageData", 15)); cout << "testing operator <" << endl; cout << pages_[0].path().string() << (pages_[0] < pages_[1]? " < " : " > ") << pages_[1].path().string() << endl; cout << pages_[1].path().string() << (pages_[1] < pages_[2]? " < " : " > ") << pages_[2].path().string() << endl; cout << pages_[0].path().string() << (pages_[0] < pages_[2]? " < " : " > ") << pages_[2].path().string() << endl; cout << "sorting" << endl; BOOST_FOREACH (Page p, pages_) cout << p.path().string() << endl; sort(pages_.begin(), pages_.end()); cout << "done sorting\n"; BOOST_FOREACH (Page p, pages_) cout << p.path().string() << endl; cout << "checking datas" << endl; BOOST_FOREACH (Page p, pages_) { char data[p.size() + 1]; strncpy((char*)&data, p.data(), p.size()); data[p.size()] = '\0'; cout << p.path().string() << " " << data << endl; } cout << "done Creating Book" << endl; } private: deque<Page> pages_; fs::path path_; }; int main() { Book* book = new Book("/some/path/"); }

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  • C: Proper syntax for allocating memory using pointers to pointers.

    - by ~kero-05h
    This is my first time posting here, hopefully I will not make a fool of myself. I am trying to use a function to allocate memory to a pointer, copy text to the buffer, and then change a character. I keep getting a segfault and have tried looking up the answer, my syntax is probably wrong, I could use some enlightenment. /* My objective is to pass a buffer to my Copy function, allocate room, and copy text to it. Then I want to modify the text and print it.*/ #include <stdio.h> #include <stdlib.h> #include <string.h> int Copy(char **Buffer, char *Text); int main() { char *Text = malloc(sizeof(char) * 100); char *Buffer; strncpy(Text, "1234567890\n", 100); Copy(&Buffer, Text); } int Copy(char **Buffer, char *Text) { int count; count = strlen(Text)+1; *Buffer = malloc(sizeof(char) * count); strncpy(*Buffer, Text, 5); *Buffer[2] = 'A'; /* This results in a segfault. "*Buffer[1] = 'A';" results in no differece in the output. */ printf("%s\n", *Buffer); }

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  • Problem with passing array of pointers to struct among functions in C

    - by karatemonkey
    The Code that follows segfaults on the call to strncpy and I can't see what I am doing wrong. I need another set of eyes to look it this. Essentially I am trying to alloc memory for a struct that is pointed to by an element in a array of pointers to struct. #include <stdio.h> #include <stdlib.h> #include <string.h> #define MAX_POLICY_NAME_SIZE 64 #define POLICY_FILES_TO_BE_PROCESSED "SPFPolicyFilesReceivedOffline\0" typedef struct TarPolicyPair { int AppearanceTime; char *IndividualFile; char *FullPolicyFile; } PolicyPair; enum { bwlist = 0, fzacts, atksig, rules, MaxNumberFileTypes }; void SPFCreateIndividualPolicyListing(PolicyPair *IndividualPolicyPairtoCreate ) { IndividualPolicyPairtoCreate = (PolicyPair *) malloc(sizeof(PolicyPair)); IndividualPolicyPairtoCreate->IndividualFile = (char *)malloc((MAX_POLICY_NAME_SIZE * sizeof(char))); IndividualPolicyPairtoCreate->FullPolicyFile = (char *)malloc((MAX_POLICY_NAME_SIZE * sizeof(char))); IndividualPolicyPairtoCreate->AppearanceTime = 0; memset(IndividualPolicyPairtoCreate->IndividualFile, '\0', (MAX_POLICY_NAME_SIZE * sizeof(char))); memset(IndividualPolicyPairtoCreate->FullPolicyFile, '\0', (MAX_POLICY_NAME_SIZE * sizeof(char))); } void SPFCreateFullPolicyListing(SPFPolicyPair **CurrentPolicyPair, char *PolicyName, char *PolicyRename) { int i; for(i = 0; i < MaxNumberFileTypes; i++) { CreateIndividualPolicyListing((CurrentPolicyPair[i])); // segfaults on this call strncpy((*CurrentPolicyPair)[i].IndividualFile, POLICY_FILES_TO_BE_PROCESSED, (SPF_POLICY_NAME_SIZE * sizeof(char))); } } int main() { SPFPolicyPair *CurrentPolicyPair[MaxNumberFileTypes] = {NULL, NULL, NULL, NULL}; int i; CreateFullPolicyListing(&CurrentPolicyPair, POLICY_FILES_TO_BE_PROCESSED, POLICY_FILES_TO_BE_PROCESSED); return 0; }

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  • Strange things appear on running the program

    - by FILIaS
    Hey! I'm fixing a program but I'm facing a problem and I cant really realize what's the wrong on the code. I would appreciate any help. I didnt post all the code...but i think with this part you can get an idea of it. With the following function enter() I wanna add user commands' datas to a list. eg. user give the command: "enter james bond 007 gun" 'james' is supposed to be the name, 'bond' the surname, 007 the amount and the rest is the description. I use strtok in order to 'cut' the command,then i put each name on a temp array. Then i call InsertSort in order to put the datas on a linked list but in alphabetical order depending on the surname that users give. I wanna keep the list on order and put each time the elements on the right position. /* struct for all the datas that user enters on file*/ typedef struct catalog { char short_name[50]; char surname[50]; signed int amount; char description[1000]; struct catalog *next; }catalog,*catalogPointer; catalogPointer current; catalogPointer head = NULL; void enter(void)//user command: enter <name> <surname> <amount> <description> { int n,j=2,k=0; char temp[1500]; char command[1500]; while (command[j]!=' ' && command[j]!='\0') { temp[k]=command[j]; j++; k++; } temp[k]='\0'; char *curToken = strtok(temp," "); printf("temp is:%s \n",temp); char short_name[50],surname[50],description[1000]; signed int amount; //short_name=(char *)malloc(sizeof (char *)); //surname=(char *)malloc(sizeof (char *)); //description=(char *)malloc(sizeof (char *)); //amount=(int *)malloc(sizeof (int *)); printf("\nWhat you entered for saving:\n"); for (n = 0; curToken !='\0'; ++n) { if (curToken) { strncpy(short_name, curToken, sizeof (char *)); / } printf("Short Name: %s \n",short_name); curToken = strtok(NULL," "); if (curToken) strncpy(surname, curToken, sizeof (char *)); / printf("SurName: %s \n",surname); curToken = strtok(NULL," "); if (curToken) { char *chk; amount = (int) strtol(curToken, &chk, 10); if (!isspace(*chk) && *chk != 0) fprintf(stderr,"Warning: expected integer value for amount, received %s instead\n",curToken); } printf("Amount: %d \n",amount); curToken = strtok(NULL,"\0"); if (curToken) { strncpy(description, curToken, sizeof (char *)); } printf("Description: %s \n",description); break; } if (findEntryExists(head, surname) != NULL) printf("\nAn entry for <%s %s> is already in the catalog!\nNew entry not entered.\n",short_name,surname); else { printf("\nTry to entry <%s %s %d %s> in the catalog list!\n",short_name,surname,amount,description); InsertSort(&head,short_name, surname, amount, description); printf("\n**Entry done!**\n"); } // Maintain the list in alphabetical order by surname. } /********Uses special case code for the head end********/ void SortedInsert(catalog** headRef, catalogPointer newNode,char short_name[],char surname[],signed int amount,char description[]) { strcpy(newNode->short_name, short_name); strcpy(newNode->surname, surname); newNode->amount=amount; strcpy(newNode->description, description); // Special case for the head end if (*headRef == NULL||(*headRef)->surname >= newNode->surname) { newNode->next = *headRef; *headRef = newNode; } else { // Locate the node before the point of insertion catalogPointer current = *headRef; catalogPointer temp=current->next; while ( temp!=NULL ) { if(strcmp(temp->surname,newNode->surname)<0 ) current = temp; } newNode->next = temp; temp = newNode; } } // Given a list, change it to be in sorted order (using SortedInsert()). void InsertSort(catalog** headRef,char short_name[],char surname[],signed int amount,char description[]) { catalogPointer result = NULL; // build the answer here catalogPointer current = *headRef; // iterate over the original list catalogPointer next; while (current!=NULL) { next = current->next; // tricky - note the next pointer before we change it SortedInsert(&result,current,short_name,surname,amount,description); current = next; } *headRef = result; } Running the program I get these strange things (garbage?)... Choose your selection: enter james bond 007 gun Your command is: enter james bond 007 gun temp is:james What you entered for saving: Short Name: james SurName: Amount: 0 Description: 0T?? Try to entry james 0 0T?? in the catalog list! Entry done! Also I'm facing a problem on how to use the 'malloc' on this program. Thanks in advance. . .

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  • C -Segmentation fault !

    - by FILIaS
    It seems at least weird to me... The program runs normally.But after I call the enter() function for the 4th time,there is a segmentation fault!I would appreciate any help. With the following function enter() I wanna add user commands' datas to a list. [Some part of the code is already posted on another question of me, but I think I should post it again...as it's a different problem I'm facing now.] /* struct for all the datas that user enters on file*/ typedef struct catalog { char short_name[50]; char surname[50]; signed int amount; char description[1000]; struct catalog *next; }catalog,*catalogPointer; catalogPointer current; catalogPointer head = NULL; void enter(void) //user command: i <name> <surname> <amount> <description> { int n,j=2,k=0; char temp[1500]; char *short_name,*surname,*description; signed int amount; char* params = strchr(command,' ') + 1; //strchr returns a pointer to the 1st space on the command.U want a pointer to the char right after that space. strcpy(temp, params); //params is saved as temp. char *curToken = strtok(temp," "); //strtok cuts 'temp' into strings between the spaces and saves them to 'curToken' printf("temp is:%s \n",temp); printf("\nWhat you entered for saving:\n"); for (n = 0; curToken; ++n) //until curToken ends: { if (curToken) { short_name = malloc(strlen(curToken) + 1); strncpy(short_name, curToken, sizeof (short_name)); } printf("Short Name: %s \n",short_name); curToken = strtok(NULL," "); if (curToken) { surname = malloc(strlen(curToken) + 1); strncpy(surname, curToken,sizeof (surname)); } printf("SurName: %s \n",surname); curToken = strtok(NULL," "); if (curToken) { //int * amount= malloc(sizeof (signed int *)); char *chk; amount = (int) strtol(curToken, &chk, 10); if (!isspace(*chk) && *chk != 0) fprintf(stderr,"Warning: expected integer value for amount, received %s instead\n",curToken); } printf("Amount: %d \n",amount); curToken = strtok(NULL,"\0"); if (curToken) { description = malloc(strlen(curToken) + 1); strncpy(description, curToken, sizeof (description)); } printf("Description: %s \n",description); break; } if (findEntryExists(head, surname,short_name) != NULL) //call function in order to see if entry exists already on the catalog printf("\nAn entry for <%s %s> is already in the catalog!\nNew entry not entered.\n",short_name,surname); else { printf("\nTry to entry <%s %s %d %s> in the catalog list!\n",short_name,surname,amount,description); newEntry(&head,short_name,surname,amount,description); printf("\n**Entry done!**\n"); } // Maintain the list in alphabetical order by surname. } catalogPointer findEntryExists (catalogPointer head, char num[],char first[]) { catalogPointer p = head; while (p != NULL && strcmp(p->surname, num) != 0 && strcmp(p->short_name,first) != 0) { p = p->next; } return p; } catalogPointer newEntry (catalog** headRef,char short_name[], char surname[], signed int amount, char description[]) { catalogPointer newNode = (catalogPointer)malloc(sizeof(catalog)); catalogPointer first; catalogPointer second; catalogPointer tmp; first=head; second=NULL; strcpy(newNode->short_name, short_name); strcpy(newNode->surname, surname); newNode->amount=amount; strcpy(newNode->description, description); while (first!=NULL) { if (strcmp(surname,first->surname)>0) second=first; else if (strcmp(surname,first->surname)==0) { if (strcmp(short_name,first->short_name)>0) second=first; } first=first->next; } if (second==NULL) { newNode->next=head; head=newNode; } else //SEGMENTATION APPEARS WHEN IT GETS HERE! { tmp=second->next; newNode->next=tmp; first->next=newNode; } } UPDATE: SegFault appears only when it gets on the 'else' loop of InsertSort() function. I observed that segmentation fault appears when i try to put on the list names that are after it. For example, if in the list exists: [Name:b Surname:b Amount:6 Description:b] [Name:c Surname:c Amount:5 Description:c] [Name:d Surname:d Amount:4 Description:d] [Name:e Surname:e Amount:3 Description:e] [Name:g Surname:g Amount:2 Description:g] [Name:x Surname:x Amount:1 Description:x] and i put: " x z 77 gege" there is a segmentation but if i put "x a 77 gege" it continues normally....

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  • C -Segmentation fault after the 4th call of the function!

    - by FILIaS
    It seems at least weird to me... The program runs normally.But after I call the enter() function for the 4th time,there is a segmentation fault!I would appreciate any help. With the following function enter() I wanna add user commands' datas to a list. [Some part of the code is already posted on another question of me, but I think I should post it again...as it's a different problem I'm facing now.] /* struct for all the datas that user enters on file*/ typedef struct catalog { char short_name[50]; char surname[50]; signed int amount; char description[1000]; struct catalog *next; }catalog,*catalogPointer; catalogPointer current; catalogPointer head = NULL; void enter(void) //user command: i <name> <surname> <amount> <description> { int n,j=2,k=0; char temp[1500]; char *short_name,*surname,*description; signed int amount; char* params = strchr(command,' ') + 1; //strchr returns a pointer to the 1st space on the command.U want a pointer to the char right after that space. strcpy(temp, params); //params is saved as temp. char *curToken = strtok(temp," "); //strtok cuts 'temp' into strings between the spaces and saves them to 'curToken' printf("temp is:%s \n",temp); printf("\nWhat you entered for saving:\n"); for (n = 0; curToken; ++n) //until curToken ends: { if (curToken) { short_name = malloc(strlen(curToken) + 1); strncpy(short_name, curToken, sizeof (short_name)); } printf("Short Name: %s \n",short_name); curToken = strtok(NULL," "); if (curToken) { surname = malloc(strlen(curToken) + 1); strncpy(surname, curToken,sizeof (surname)); } printf("SurName: %s \n",surname); curToken = strtok(NULL," "); if (curToken) { //int * amount= malloc(sizeof (signed int *)); char *chk; amount = (int) strtol(curToken, &chk, 10); if (!isspace(*chk) && *chk != 0) fprintf(stderr,"Warning: expected integer value for amount, received %s instead\n",curToken); } printf("Amount: %d \n",amount); curToken = strtok(NULL,"\0"); if (curToken) { description = malloc(strlen(curToken) + 1); strncpy(description, curToken, sizeof (description)); } printf("Description: %s \n",description); break; } if (findEntryExists(head, surname,short_name) != NULL) //call function in order to see if entry exists already on the catalog printf("\nAn entry for <%s %s> is already in the catalog!\nNew entry not entered.\n",short_name,surname); else { printf("\nTry to entry <%s %s %d %s> in the catalog list!\n",short_name,surname,amount,description); newEntry(&head,short_name,surname,amount,description); printf("\n**Entry done!**\n"); } // Maintain the list in alphabetical order by surname. } catalogPointer findEntryExists (catalogPointer head, char num[],char first[]) { catalogPointer p = head; while (p != NULL && strcmp(p->surname, num) != 0 && strcmp(p->short_name,first) != 0) { p = p->next; } return p; } catalogPointer newEntry (catalog** headRef,char short_name[], char surname[], signed int amount, char description[]) { catalogPointer newNode = (catalogPointer)malloc(sizeof(catalog)); catalogPointer first; catalogPointer second; catalogPointer tmp; first=head; second=NULL; strcpy(newNode->short_name, short_name); strcpy(newNode->surname, surname); newNode->amount=amount; strcpy(newNode->description, description); //SEGMENTATION ON THE 4TH RUN OF PROGRAM STOPS HERE depending on the names each time it gets! while (first!=NULL) { if (strcmp(surname,first->surname)>0) second=first; else if (strcmp(surname,first->surname)==0) { if (strcmp(short_name,first->short_name)>0) second=first; } first=first->next; } if (second==NULL) { newNode->next=head; head=newNode; } else { tmp=second->next; newNode->next=tmp; first->next=newNode; } }

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  • how to insert multiple characters into a string in C [closed]

    - by John Li
    I wish to insert some characters into a string in C: Example: char string[20] = "20120910T090000"; I want to make it something like "2012-09-10-T-0900-00" My code so far: void append(char subject[],char insert[], int pos) { char buf[100]; strncpy(buf, subject, pos); int len = strlen(buf); strcpy(buf+len, insert); len += strlen(insert); strcpy(buf+len, subject+pos); strcpy(subject, buf); } When I call this the first time I get: 2012-0910T090000 However when I call it a second time I get: 2012-0910T090000-10T090000 Any help is appreciated

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  • snprintf vs strcpy(etc) in c

    - by monkeyking
    For doing string concatenation I've been doing basic strcpy,strncpy of char* buffers. Then I learned about the snprintf and friends. Should I stick with my strcpy,strcpy + \0 terminiation. Or should I just use snprintf in the future? thanks

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  • What's wrong with cplusplus.com?

    - by Kerrek SB
    This is perhaps not a perfectly suitable forum for this question, but let me give it a shot, at the risk of being moved away. There are several references for the C++ standard library, including the invaluable ISO standard, MSDN, IBM, cppreference, and cplusplus. Personally, when writing C++ I need a reference that has quick random access, short load times and usage examples, and I've been finding cplusplus.com pretty useful. However, I've been hearing negative opinions about that website frequently here on SO, so I would like to get specific: What are the errors, misconceptions or bad pieces of advice given by cplusplus.com? What are the risks of using it to make coding decisions? Let me add this point: I want to be able to answer questions here on SO with accurate quotes of the standard, and thus I would like to post immediately-usable links, and cplusplus.com would have been my choice site were it not for this issue. Update: There have been many great responses, and I have seriously changed my view on cplusplus.com. I'd like to list a few choice results here; feel free to suggest more (and keep posting answers). As of June 29, 2011: Incorrect description of some algorithms (e.g. remove). Information about the behaviour of functions is sometimes incorrect (atoi), fails to mention special cases (strncpy), or omits vital information (iterator invalidation). Examples contain deprecated code (#include style). Inexact terminology is doing a disservice to learners and the general community ("STL", "compiler" vs "toolchain"). Incorrect and misleading description of the typeid keyword.

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  • What's wrong with cplusplus.com?

    - by Kerrek SB
    This is perhaps not a perfectly suitable forum for this question, but let me give it a shot, at the risk of being moved away. There are several references for the C++ standard library, including the invaluable ISO standard, MSDN, IBM, cppreference, and cplusplus. Personally, when writing C++ I need a reference that has quick random access, short load times and usage examples, and I've been finding cplusplus.com pretty useful. However, I've been hearing negative opinions about that website frequently here on SO, so I would like to get specific: What are the errors, misconceptions or bad pieces of advice given by cplusplus.com? What are the risks of using it to make coding decisions? Let me add this point: I want to be able to answer questions here on SO with accurate quotes of the standard, and thus I would like to post immediately-usable links, and cplusplus.com would have been my choice site were it not for this issue. Update: There have been many great responses, and I have seriously changed my view on cplusplus.com. I'd like to list a few choice results here; feel free to suggest more (and keep posting answers). As of June 29, 2011: Incorrect description of some algorithms (e.g. remove). Information about the behaviour of functions is sometimes incorrect (atoi), fails to mention special cases (strncpy), or omits vital information (iterator invalidation). Examples contain deprecated code (#include style). Inexact terminology is doing a disservice to learners and the general community ("STL", "compiler" vs "toolchain"). Incorrect and misleading description of the typeid keyword.

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  • Faulting DLL (ISAPI Filter)...

    - by Brad
    I wrote this ISAPI filter to rewrite the URL because we had some sites that moved locations... Basically the filter looks at the referrer, and if it's the local server, it looks at the requested URL and compared it to the full referrer. If the first path is identical, nothing is done, however if not, it takes the first path from the full referrer and prepends it to the URL. For example: /Content/imgs/img.jpg from a referrer of http://myserver/wr/apps/default.htm would be rewritten as /wr/Content/imgs/img.jpg. When I view the log file, everything looks good. However the DLL keeps faulting with the following information: Faulting application w3wp.exe, version 6.0.3790.3959, faulting module URLRedirector.dll, version 0.0.0.0, fault address 0x0002df25. Here's the code: #include <windows.h> #include <stdio.h> #include <stdlib.h> #include <httpfilt.h> #include <time.h> #include <string.h> #ifdef _DEBUG #define TO_FILE // uncomment out to use a log file #ifdef TO_FILE #define DEST ghFile #define DebugMsg(x) WriteToFile x; HANDLE ghFile; #define LOGFILE "W:\\Temp\\URLRedirector.log" void WriteToFile (HANDLE hFile, char *szFormat, ...) { char szBuf[1024]; DWORD dwWritten; va_list list; va_start (list, szFormat); vsprintf (szBuf, szFormat, list); hFile = CreateFile (LOGFILE, GENERIC_WRITE, 0, NULL, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL); if (hFile != INVALID_HANDLE_VALUE) { SetFilePointer (hFile, 0, NULL, FILE_END); WriteFile (hFile, szBuf, lstrlen (szBuf), &dwWritten, NULL); CloseHandle (hFile); } va_end (list); } #endif #endif BOOL WINAPI __stdcall GetFilterVersion(HTTP_FILTER_VERSION *pVer) { /* Specify the types and order of notification */ pVer->dwFlags = (SF_NOTIFY_ORDER_HIGH | SF_NOTIFY_SECURE_PORT | SF_NOTIFY_NONSECURE_PORT | SF_NOTIFY_PREPROC_HEADERS | SF_NOTIFY_END_OF_NET_SESSION); pVer->dwFilterVersion = HTTP_FILTER_REVISION; strcpy(pVer->lpszFilterDesc, "URL Redirector, Version 1.0"); return TRUE; } DWORD WINAPI __stdcall HttpFilterProc(HTTP_FILTER_CONTEXT *pfc, DWORD NotificationType, VOID *pvData) { CHAR *pPhysPath; PHTTP_FILTER_URL_MAP pURLMap; PHTTP_FILTER_PREPROC_HEADERS pHeaderInfo; CHAR szReferrer[255], szServer[255], szURL[255], szNewURL[255]; DWORD dwRSize = sizeof(szReferrer); DWORD dwSSize = sizeof(szServer); DWORD dwUSize = sizeof(szURL); int iTmp, iTmp2; CHAR *pos, tmp[255], *tmp2; switch (NotificationType) { case SF_NOTIFY_PREPROC_HEADERS : pHeaderInfo = (PHTTP_FILTER_PREPROC_HEADERS)pvData; if (pfc->GetServerVariable(pfc, "HTTP_REFERER", szReferrer, &dwRSize)) { DebugMsg(( DEST, "Referrer: %s\r\n", szReferrer )); if (pfc->GetServerVariable(pfc, "SERVER_NAME", szServer, &dwSSize)) DebugMsg(( DEST, "Server Name: %s\r\n", szServer )); if (pHeaderInfo->GetHeader(pfc, "URL", szURL, &dwUSize)) DebugMsg(( DEST, "URL: %s\r\n", szURL )); iTmp = strnstr(szReferrer, szServer, strlen(szReferrer)); if(iTmp > 0) { //Referred is our own server... strcpy(tmp, szReferrer + iTmp); DebugMsg(( DEST, "tmp: %s - %d\r\n", tmp, strlen(tmp) )); pos = strchr(tmp+1, '/'); DebugMsg(( DEST, "pos: %s - %d\r\n", pos, strlen(pos) )); iTmp2 = strlen(tmp) - strlen(pos) + 1; strncpy(tmp2, tmp, iTmp2); tmp2[iTmp2] = '\0'; DebugMsg(( DEST, "tmp2: %s\r\n", tmp2)); if(strncmp(szURL, tmp2, iTmp2) != 0) { //First paths don't match, create new URL... strncpy(szNewURL, tmp2, iTmp2-1); strcat(szNewURL, szURL); DebugMsg(( DEST, "newURL: %s\r\n", szNewURL)); pHeaderInfo->SetHeader(pfc, "URL", szNewURL); return SF_STATUS_REQ_HANDLED_NOTIFICATION; } } } break; default : break; } return SF_STATUS_REQ_NEXT_NOTIFICATION; } /* simple function to compare two strings and return the position at which the compare ended */ static int strnstr ( const char *string, const char *strCharSet, int n) { int len = (strCharSet != NULL ) ? ((int)strlen(strCharSet )) : 0 ; int ret, I, J, found; if ( 0 == n || 0 == len ) { return -1; } ret = -1; found = 0; for (I = 0 ; I <= n - len && found != 1 ; I++) { J = 0 ; for ( ; J < len ; J++ ) { if (toupper(string[I + J]) != toupper(strCharSet [J])) { break; // Exit For(J) } } if ( J == len) { ret = I + (J); found = 1; } } return ret; }

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  • my version of strlcpy

    - by robUK
    Hello, gcc 4.4.4 c89 My program does a lot of string coping. I don't want to use the strncpy as it doesn't nul terminate. And I can't use strlcpy as its not portable. Just a few questions. How can I put my function those its paces to ensure that it is completely safe and stable. Unit testing? Is this good enough for production? size_t s_strlcpy(char *dest, const char *src, const size_t len) { size_t i = 0; /* Always copy 1 less then the destination to make room for the nul */ for(i = 0; i < len - 1; i++) { /* only copy up to the first nul is reached */ if(*src != '\0') { *dest++ = *src++; } else { break; } } /* nul terminate the string */ *dest = '\0'; /* Return the number of bytes copied */ return i; } Many thanks for any suggestions,

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  • difference fixed width strings and zero-terminated strings

    - by robUK
    Hello, gcc 4.4.4 c89 I got into a recent discussion about "fixed width strings" and "zero terminated strings". When I think about this. They seem to be the same thing. A string with a terminating null. i.e. char *name = "Joe bloggs"; Is a fixed width string that cannot be changed. And also has a terminating null. Also in the discussion I was told that strncpy should never been used on 'zero terminated strings'. Many thanks for any susgestions,

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  • Why this function overloading is not working?

    - by Jack
    class CConfFile { public: CConfFile(const std::string &FileName); ~CConfFile(); ... std::string GetString(const std::string &Section, const std::string &Key); void GetString(const std::string &Section, const std::string &Key, char *Buffer, unsigned int BufferSize); ... } string CConfFile::GetString(const string &Section, const string &Key) { return GetKeyValue(Section, Key); } void GetString(const string &Section, const string &Key, char *Buffer, unsigned int BufferSize) { string Str = GetString(Section, Key); // *** ERROR *** strncpy(Buffer, Str.c_str(), Str.size()); } Why do I get an error too few arguments to function ‘void GetString(const std::string&, const std::string&, char*, unsigned int)' at the second function ? Thanks

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  • Has anyone properly interpreted HTTP request based on this demo of winpcap?

    - by httpinterpret
    The example is here, and I tried it by changing the filter to tcp and dst port 80 and the following: void packet_handler(u_char *param, const struct pcap_pkthdr *header, const u_char *pkt_data) { .... ip_len = (ih->ver_ihl & 0xf) * 4; tcp_len = (((u_char*)ih)[ip_len + 12] >> 4) * 4; tcpPayload = (u_char*)ih + ip_len + tcp_len; /* start of url - skip "GET " */ url = tcpPayload + 4; end_url = strchr((char*)url, ' '); url_length = end_url - url; final_url = (u_char*)malloc(url_length + 1); strncpy((char*)final_url, (char*)url, url_length); final_url[url_length] = '\0'; printf("%s\n", final_url); .... } But through debug, I see tcpPayload is full of messy code,not supposed "GET ..." stuff. What's wrong with my implement?

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