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• SWIG & C/C++ Python API connected - SEGFAULT

  - by user289637

  Hello, my task is to create dual program. At the beginning I start C program that calls throught C/C++ API of Python some Python method. The called method after that call a function that is created with SWIG. I show you my sample also with backtrace from gdb after I am given Segmentation fault. main.c: #include <Python.h> #include <stdio.h> #include "utils.h" int main(int argc, char** argv) { printf("Calling from C !\n"); increment(); int i; for(i = 0; i < 11; ++i) { Py_Initialize(); PyObject *pname = PyString_FromString("py_function"); PyObject *module = PyImport_Import(pname); PyObject *dict = PyModule_GetDict(module); PyObject *func = PyDict_GetItemString(dict, "ink"); PyObject_CallObject(func, NULL); Py_DECREF(module); Py_DECREF(pname); printf("\tbefore finalize\n"); Py_Finalize(); printf("\tafter finalize\n"); } return 0; } utils.c #include <stdio.h> #include "utils.h" void increment(void) { printf("Incremention counter to: %u\n", ++counter); } py_function.py #!/usr/bin/python2.6 '''py_function.py - Python source designed to demonstrate the use of python embedding''' import utils def ink(): print 'I am gonna increment !' utils.increment() and last think is my Makefile & SWIG configure file Makefile: CC=gcc CFLAGS=-c -g -Wall -std=c99 all: main main: main.o utils.o utils_wrap.o $(CC) main.o utils.o -lpython2.6 -o sample swig -Wall -python -o utils_wrap.c utils.i $(CC) utils.o utils_wrap.o -shared -o _utils.so main.o: main.c $(CC) $(CFLAGS) main.c -I/usr/include/python2.6 -o main.o utils.o: utils.c utils.h $(CC) $(CFLAGS) -fPIC utils.c -o $@ utils_wrap.o: utils_wrap.c $(CC) -c -fPIC utils_wrap.c -I/usr/include/python2.6 -o $@ clean: rm -rf *.o The program is called by ./main and there is output: (gdb) run Starting program: /home/marxin/Programming/python2/sample [Thread debugging using libthread_db enabled] Calling from C ! Incremention counter to: 1 I am gonna increment ! Incremention counter to: 2 before finalize after finalize I am gonna increment ! Incremention counter to: 3 before finalize after finalize I am gonna increment ! Incremention counter to: 4 before finalize after finalize Program received signal SIGSEGV, Segmentation fault. 0xb7ed3e4e in PyObject_Malloc () from /usr/lib/libpython2.6.so.1.0 Backtrace: (gdb) backtrace #0 0xb7ed3e4e in PyObject_Malloc () from /usr/lib/libpython2.6.so.1.0 #1 0xb7ca2b2c in ?? () #2 0xb7f8dd40 in ?? () from /usr/lib/libpython2.6.so.1.0 #3 0xb7eb014c in ?? () from /usr/lib/libpython2.6.so.1.0 #4 0xb7f86ff4 in ?? () from /usr/lib/libpython2.6.so.1.0 #5 0xb7f99820 in ?? () from /usr/lib/libpython2.6.so.1.0 #6 0x00000001 in ?? () #7 0xb7f8dd40 in ?? () from /usr/lib/libpython2.6.so.1.0 #8 0xb7f4f014 in _PyObject_GC_Malloc () from /usr/lib/libpython2.6.so.1.0 #9 0xb7f99820 in ?? () from /usr/lib/libpython2.6.so.1.0 #10 0xb7f4f104 in _PyObject_GC_NewVar () from /usr/lib/libpython2.6.so.1.0 #11 0xb7ee8760 in _PyType_Lookup () from /usr/lib/libpython2.6.so.1.0 #12 0xb7f99820 in ?? () from /usr/lib/libpython2.6.so.1.0 #13 0x00000001 in ?? () #14 0xb7f8dd40 in ?? () from /usr/lib/libpython2.6.so.1.0 #15 0xb7ef13ed in ?? () from /usr/lib/libpython2.6.so.1.0 #16 0xb7f86ff4 in ?? () from /usr/lib/libpython2.6.so.1.0 #17 0x00000001 in ?? () #18 0xbfff0c34 in ?? () #19 0xb7e993c3 in ?? () from /usr/lib/libpython2.6.so.1.0 #20 0x00000001 in ?? () #21 0xbfff0c70 in ?? () #22 0xb7f99da0 in ?? () from /usr/lib/libpython2.6.so.1.0 #23 0xb7f86ff4 in ?? () from /usr/lib/libpython2.6.so.1.0 #24 0xb7f86ff4 in ?? () from /usr/lib/libpython2.6.so.1.0 #25 0x080a6b0c in ?? () #26 0x080a6b0c in ?? () #27 0xb7e99420 in PyObject_CallFunctionObjArgs () from /usr/lib/libpython2.6.so.1.0 #28 0xb7f86ff4 in ?? () from /usr/lib/libpython2.6.so.1.0 #29 0xb7f86ff4 in ?? () from /usr/lib/libpython2.6.so.1.0 #30 0x800e55eb in ?? () #31 0x080a6b0c in ?? () #32 0xb7e9958c in PyObject_IsSubclass () from /usr/lib/libpython2.6.so.1.0 #33 0xb7f8dd40 in ?? () from /usr/lib/libpython2.6.so.1.0 #34 0x080a9020 in ?? () #35 0xb7fb78f0 in PyFPE_counter () from /usr/lib/libpython2.6.so.1.0 #36 0xb7f86ff4 in ?? () from /usr/lib/libpython2.6.so.1.0 #37 0x00000000 in ?? () Thanks for your help and advices, marxin

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• Autocorrelation method for pitch determination.. whats d input data form..?

  - by harsh

  i hav read a code for pitch determination using autocorrelation method. can anybody please tell wht wud b d input data(passed as argument to DetectPitch()) function here: double DetectPitch(short* data) { int sampleRate = 2048; //Create sine wave double *buffer = malloc(1024*sizeof(short)); double amplitude = 0.25 * 32768; //0.25 * max length of short double frequency = 726.0; for (int n = 0; n < 1024; n++) { buffer[n] = (short)(amplitude * sin((2 * 3.14159265 * n * frequency) / sampleRate)); } doHighPassFilter(data); printf("Pitch from sine wave: %f\n",detectPitchCalculation(buffer, 50.0, 1000.0, 1, 1)); printf("Pitch from mic: %f\n",detectPitchCalculation(data, 50.0, 1000.0, 1, 1)); return 0; }

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• How to output floating point numbers with a custom output format in C++?

  - by Victor Liu

  The problem is that I want to output Mathematica compatible floating point numbers. The only difference with the standard IOStream or printf output format is that the exponential e is replaced by *^: Standard C/C++ output format: 1.23e-4 Mathematica format: 1.23*^-4 Is there a way to manipulate streams to achieve this effect? My original idea was just to use istringstream and dump it to a string and then replace all the e's. I would also be okay if someone posted code to parse through the bits of the floating point number and output it directly (i.e. a printf("%e") replacement).

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• What coding standards do you follow?

  - by Mark Szymanski

  I was just curious what coding standards people followed. I for one use the following: Brackets ALWAYS go on the next line. For instance: int main() { //Blah... } I never use code folding. (Yes my IDE's do support it (Xcode and Eclipse). Put related functions/methods single-spaced, otherwise double space. Here is an example: int foo = 0; printf("%d",foo); those are related while these are not: printf("Hello, World!"); return(0); I don't put else statements on the same line as the closing bracket for the preceding if statement. Most of the time in Java if a program needs multiple try catch statements I will just put the whole thing in one try catch.

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• SDCC and malloc() - allocating much less memory than is available

  - by Duncan Bayne

  When I run compile this code with SDCC 3.1.0, and run it on an Amstrad CPC 464 (under emulation, with WinCPC 0.9.26 running on Wine): void _test_malloc() { long idx = 0; while (1) { if (malloc(5)) { printf("%ld\r\n", ++idx); } else { printf("done"); break; } } } ... it consistently taps out at 92 malloc()s. I make that 460 bytes, which leads me to a couple of questions: What is malloc() doing on this system? I was sort of hoping for an order of magnitude more storage even on a 64kB system The behaviour is consistent on 64kB systems and 128kB systems; do I have to perform some sort of magic to access the additional memory, like manual bank switching?

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• How to set background in OpenGL captured image from OpenCV

  - by user325487

  Hey All, i'm relatively new to Artoolkitplus and openGL i'm having a tough time getting the image i capture through openCV to be set as the background image in OpenGL ... I also cannot convert the image i take through the camera using opencv to be scaled to 320x280 from 640x480 .. i also have to save my image and load if for things to work... here's my code //////////// int findMarker() { IplImage* image = cvQueryFrame( capture ); if( !capture ) { fprintf( stderr, "ERROR: capture is NULL \n" ); getchar(); return -1; } if( !image ) { fprintf( stderr, "ERROR: frame is null...\n" ); getchar(); } //cvShowImage( "Capture", frame ); //image = cvCloneImage( frame ); try{ if(!cvSaveImage("immagineTmp.jpg",image)) printf("Could not save\n"); } catch(void*) {} image = cvLoadImage("immagineTmp.jpg", 1); cvShowImage( "Image", image ); glLoadIdentity(); ////////////// glDisable(GL_DEPTH_TEST); glOrtho(0,640,0,480,-1,1); glGenTextures(1, &bgid); glBindTexture(GL_TEXTURE_2D, bgid); // Create Linear Filtered Texture glBindTexture(GL_TEXTURE_2D, bgid); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR); glTexImage2D(GL_TEXTURE_2D, 0, 3, image-width, image-height, 0, GL_RGB, GL_UNSIGNED_BYTE, image-imageData); glBindTexture(GL_TEXTURE_2D, bgid); glBegin(GL_QUADS); glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.2f, -1.0f, -2.0f); glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.2f, -1.0f, -2.0f); glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.2f, 1.0f, -2.0f); glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.2f, 1.0f, -2.0f); glEnd(); glEnable(GL_DEPTH_TEST); glLoadIdentity(); //////////// // do the OpenGL camera setup glMatrixMode(GL_PROJECTION); glLoadMatrixf(tracker-getProjectionMatrix()); int markerId = tracker-calc((unsigned char *)(image-imageData)); float conf = tracker-getConfidence(); // use the result of calc() to setup the OpenGL transformation glMatrixMode(GL_MODELVIEW); glLoadMatrixf(tracker-getModelViewMatrix()); if(markerId!=-1) { printf("\n\nFound marker %d (confidence %d%%)\n\nPose-Matrix:\n ", markerId, (int(conf*100.0f))); for(int i=0; i<16; i++) printf("%.2f %s", tracker-getModelViewMatrix()[i], (i%4==3)?"\n " : ""); } cvReleaseImage(&image); return 0; }

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• inline and member initializers

  - by Alexander

  When should I inline a member function and when should I use member initializers? My code is below.. I would like to modify it so I could make use some inline when appropriate and member initializers: #include "Books.h" Book::Book(){ nm = (char*)""; thck = 0; wght = 0; } Book::Book(const char *name, int thickness, int weight){ nm = strdup(name); thck = thickness; wght = weight; } Book::~Book(){ } const char* Book::name(){ return nm; } int Book::thickness(){ return thck; } int Book::weight(){ return wght; } // // Prints information about the book using this format: // "%s (%d mm, %d dg)\n" // void Book::print(){ printf("%s (%d mm, %d dg)\n", nm, thck, wght); } Bookcase::Bookcase(int id){ my_id = id; no_shelf = 0; } int Bookcase::id(){ return my_id; } Bookcase::~Bookcase(){ for (int i = 0; i < no_shelf; i++) delete my_shelf[i]; } bool Bookcase::addShelf(int width, int capacity){ if(no_shelf == 10) return false; else{ my_shelf[no_shelf] = new Shelf(width, capacity); no_shelf++; return true; } } bool Bookcase::add(Book *bp){ int index = -1; int temp_space = -1; for (int i = 0; i < no_shelf; i++){ if (bp->weight() + my_shelf[i]->curCapacity() <= my_shelf[i]->capacity()){ if (bp->thickness() + my_shelf[i]->curWidth() <= my_shelf[i]->width() && temp_space < (my_shelf[i]->width() - my_shelf[i]->curWidth())){ temp_space = (my_shelf[i]->width()- my_shelf[i]->curWidth()); index = i; } } } if (index != -1){ my_shelf[index]->add(bp); return true; }else return false; } void Bookcase::print(){ printf("Bookcase #%d\n", my_id); for (int i = 0; i < no_shelf; i++){ printf("--- Shelf (%d mm, %d dg) ---\n", my_shelf[i]->width(), my_shelf[i]->capacity()); my_shelf[i]->print(); } }

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• Double indirection and structures passed into a function

  - by ZPS

  I am curious why this code works: typedef struct test_struct { int id; } test_struct; void test_func(test_struct ** my_struct) { test_struct my_test_struct; my_test_struct.id=267; *my_struct = &my_test_struct; } int main () { test_struct * main_struct; test_func(&main_struct); printf("%d\n",main_struct->id); } This works, but pointing to the memory address of a functions local variable is a big no-no, right? But if i used a structure pointer and malloc, that would be the correct way, right? void test_func(test_struct ** my_struct) { test_struct *my_test_struct; my_test_struct = malloc(sizeof(test_struct)); my_test_struct->id=267; *my_struct = my_test_struct; } int main () { test_struct * main_struct; test_func(&main_struct); printf("%d\n",main_struct->id); }

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• Parenthesis operator in C. What is the effect in the following code

  - by Andre

  Hi everyone, I was playing with a macro to enable/disable traces when I came out with the following code when the macro is disabled: int main { ("Hello world"); } This code is valid and I got the desired effect (nothing happens when the macro is disabled) but I couldn't figure out what exactly is happening. Is the compiler seeing the parenthesis as a "nameless" method declaration? To make it clearer the code is : #ifdef TRACE #define trace printf("%s %d -> ",__FILE__, __LINE__);printf else #define trace #endif int main { trace("Hello world"); } Thanks in advance.

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• Why freed struct in C still has data?

  - by kliketa

  When I run this code: #include <stdio.h> typedef struct _Food { char name [128]; } Food; int main (int argc, char **argv) { Food *food; food = (Food*) malloc (sizeof (Food)); snprintf (food->name, 128, "%s", "Corn"); free (food); printf ("%d\n", sizeof *food); printf ("%s\n", food->name); } I still get 128 Corn although I have freed food. Why is this? Is memory really freed?

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• Change default Console I/O functions handle.

  - by b-gen-jack-o-neill

  Hello. Is it possible to somehow change standart I/O functions handle on Windows? Language preffered is C++. If I understand it right, by selecting console project, compiler just pre-allocate console for you, and operates all standart I/O functions to work with its handle. So, what I want to do is to let one Console app actually write into another app Console buffer. I though that I could get first´s Console handle, than pass it to second app by a file (I don´t know much about interprocess comunication, and this seems easy) and than somehow use for example prinf with the first app handle. Can this be done? I know how to get console handle, but I have no idea how to redirect printf to that handle. Its just study-purpose project to more understand of OS work behind this. I am interested in how printf knows what Console it is assiciated with.

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• Why is my implementation of strcmp not returning the proper value?

  - by Avanish Giri

  Why is this printing out 0 back in main but 6 when it is inside of the strcmp function? 7 int main() 8 { 9 char* str = "test string"; 10 char* str2 = "test strong"; 11 //printf("string length = %d\n",strlen(str)); 12 13 int num = strcmp(str,str2); 14 15 printf("num = %d\n",num); 16 } 29 int strcmp(char* str, char* str2) 30 { 31 if(*str == '\0' && *str2 == '\0') 32 return 0; 33 if(*str2 - *str == 0) 34 { 35 strcmp(str+1,str2+1); 36 } 37 else 38 { 39 int num = *str2 - *str; 40 cout << "num = " <<num<<endl; 41 return num; 42 } 43 } The output is: num = 6 num = 0 Why is it printing 0 when obviously the value that it should be returning is 6?

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• Behavior with primitive data types' value out of range & C99's PRI* macros

  - by Yktula

  Say we have an 8-bit unsigned integer n (UINT8_MAX=255); what is the behavior of the compiler for n=256? Where can I find a table of default behavior when the value of a data type is out of range for different data types? Is there a pattern to how they behave when set out of range? #include <stdio.h> #include <inttypes.h> uint8_t n = UINT8_MAX; int main() { printf("%hhu ",n++); printf("%hhu",n); return 0; } Compiling with gcc -std=c99 -Wall *.c, this prints: 255 0 Also, is it acceptable to use C99's PRI* macros? How are they named?

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• About This Code

  - by the-ifl

  Hi Guys , well I have a simple and a stupid question !! in this code what is the role of the symbol "%3d"...I Now That % mean refer To Variable ...... This is The Code : #include <stdio.h> int main(void) { int t, i, num[3][4]; for(t=0; t<3; ++t) for(i=0; i<4; ++i) num[t][i] = (t*4)+i+1; /* now print them out */ for(t=0; t<3; ++t) { for(i=0; i<4; ++i) printf("%3d ", num[t][i]); printf("\n"); } return 0; }

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• C segmentation fault before/during return statement

  - by wolfPack88

  I print the value that I'm returning right before my return statement, and tell my code to print the value that was returned right after the function call. However, I get a segmentation fault after my first print statement and before my second (also interesting to note, this always happens on the third time the function is called; never the first or the second, never fourth or later). I tried printing out all of the data that I'm working on to see if the rest of my code was doing something it maybe shouldn't, but my data up to that point looks fine. Here's the function: int findHydrogen(struct Amino* amino, int nPos, float* diff, int totRead) { struct Atom* atoms; int* bonds; int numBonds; int i; int retVal; int numAtoms; numAtoms = (*amino).numAtoms; atoms = (struct Atom *) malloc(sizeof(struct Atom) * numAtoms); atoms = (*amino).atoms; numBonds = atoms[nPos].numBonds; bonds = (int *) malloc(sizeof(int) * numBonds); bonds = atoms[nPos].bonds; for(i = 0; i < (*amino).numAtoms; i++) printf("ATOM\t\t%d %s\t0001\t%f\t%f\t%f\n", i + 1, atoms[i].type, atoms[i].x, atoms[i].y, atoms[i].z); for(i = 0; i < numBonds; i++) if(atoms[bonds[i] - totRead].type[0] == 'H') { diff[0] = atoms[bonds[i] - totRead].x - atoms[nPos].x; diff[1] = atoms[bonds[i] - totRead].y - atoms[nPos].y; diff[2] = atoms[bonds[i] - totRead].z - atoms[nPos].z; retVal = bonds[i] - totRead; bonds = (int *) malloc(sizeof(int)); free(bonds); atoms = (struct Atom *) malloc(sizeof(struct Atom)); free(atoms); printf("2 %d\n", retVal); return retVal; } } As I mentioned before, it works fine the first two times I run it, the third time it prints the correct value of retVal, then seg faults somewhere before it gets to where I called the function, which I do as: hPos = findHydrogen((&aminoAcid[i]), nPos, diff, totRead); printf("%d\n", hPos);

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• Problem overridding virtual function

  - by William

  Okay, I'm writing a game that has a vector of a pairent class (enemy) that s going to be filled with children classes (goomba, koopa, boss1) and I need to make it so when I call update it calls the childclasses respective update. I have managed to create a example of my problem. #include <stdio.h> class A{ public: virtual void print(){printf("Hello from A");} }; class B : public A{ public: void print(){printf("Hello from B");} }; int main(){ A ab = B(); ab.print(); while(true){} } Output wanted: "Hello from B" Output got: "Hello from A" How do I get it to call B's print function?

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• How do you determine using stat() whether a file is a symbolic link?

  - by hora

  I basically have to write a clone of the UNIX ls command for a class, and I've got almost everything working. One thing I can't seem to figure out how to do is check whether a file is a symbolic link or not. From the man page for stat(), I see that there is a mode_t value defined, S_IFLNK. This is how I'm trying to check whether a file is a sym-link, with no luck (note, stbuf is the buffer that stat() returned the inode data into): switch(stbuf.st_mode & S_IFMT){ case S_IFLNK: printf("this is a link\n"); break; case S_IFREG: printf("this is not a link\n"); break; } My code ALWAYS prints this is not a link even if it is, and I know for a fact that the said file is a symbolic link since the actual ls command says so, plus I created the sym-link... Can anyone spot what I may be doing wrong? Thanks for the help!

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• converting char array into one int

  - by user1762517

  I can't use atoi, need to do it digit by digit.. How do I save it in a int.. given a char* temp put it all in one int.. #include <stdio.h> #include <string.h> #include <stdlib.h> #include <math.h> int main () { char* temp = "798654564654564654"; int i = 0; for (i = 0; i < strlen(temp); i++) { printf("%d", temp[i] - 48); } printf("\n"); }

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• Implications of trying to double free memory space in C

  - by SidNoob

  Here' my piece of code: #include <stdio.h> #include<stdlib.h> struct student{ char *name; }; int main() { struct student s; s.name = malloc(sizeof(char *)); // I hope this is the right way... printf("Name: "); scanf("%[^\n]", s.name); printf("You Entered: \n\n"); printf("%s\n", s.name); free(s.name); // This will cause my code to break } All I know is that dynamic allocation on the 'heap' needs to be freed. My question is, when I run the program, sometimes the code runs successfully. i.e. ./struct Name: Thisis Myname You Entered: Thisis Myname I tried reading this I've concluded that I'm trying to double-free a piece of memory i.e. I'm trying to free a piece of memory that is already free? (hope I'm correct here. If Yes, what could be the Security Implications of a double-free?) While it fails sometimes as its supposed to: ./struct Name: CrazyFishMotorhead Rider You Entered: CrazyFishMotorhead Rider *** glibc detected *** ./struct: free(): invalid next size (fast): 0x08adb008 *** ======= Backtrace: ========= /lib/tls/i686/cmov/libc.so.6(+0x6b161)[0xb7612161] /lib/tls/i686/cmov/libc.so.6(+0x6c9b8)[0xb76139b8] /lib/tls/i686/cmov/libc.so.6(cfree+0x6d)[0xb7616a9d] ./struct[0x8048533] /lib/tls/i686/cmov/libc.so.6(__libc_start_main+0xe6)[0xb75bdbd6] ./struct[0x8048441] ======= Memory map: ======== 08048000-08049000 r-xp 00000000 08:01 288098 /root/struct 08049000-0804a000 r--p 00000000 08:01 288098 /root/struct 0804a000-0804b000 rw-p 00001000 08:01 288098 /root/struct 08adb000-08afc000 rw-p 00000000 00:00 0 [heap] b7400000-b7421000 rw-p 00000000 00:00 0 b7421000-b7500000 ---p 00000000 00:00 0 b7575000-b7592000 r-xp 00000000 08:01 788956 /lib/libgcc_s.so.1 b7592000-b7593000 r--p 0001c000 08:01 788956 /lib/libgcc_s.so.1 b7593000-b7594000 rw-p 0001d000 08:01 788956 /lib/libgcc_s.so.1 b75a6000-b75a7000 rw-p 00000000 00:00 0 b75a7000-b76fa000 r-xp 00000000 08:01 920678 /lib/tls/i686/cmov/libc-2.11.1.so b76fa000-b76fc000 r--p 00153000 08:01 920678 /lib/tls/i686/cmov/libc-2.11.1.so b76fc000-b76fd000 rw-p 00155000 08:01 920678 /lib/tls/i686/cmov/libc-2.11.1.so b76fd000-b7700000 rw-p 00000000 00:00 0 b7710000-b7714000 rw-p 00000000 00:00 0 b7714000-b7715000 r-xp 00000000 00:00 0 [vdso] b7715000-b7730000 r-xp 00000000 08:01 788898 /lib/ld-2.11.1.so b7730000-b7731000 r--p 0001a000 08:01 788898 /lib/ld-2.11.1.so b7731000-b7732000 rw-p 0001b000 08:01 788898 /lib/ld-2.11.1.so bffd5000-bfff6000 rw-p 00000000 00:00 0 [stack] Aborted So why is it that my code does work sometimes? i.e. the compiler is not able to detect at times that I'm trying to free an already freed memory. Has it got to do something with my stack/heap size?

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• WinMain not called before main (C/C++ Program Entry Point Issue)

  - by BT

  I was under the impression that this code #include <windows.h> #include <stdio.h> int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow) { printf("WinMain\n"); return 0; } int main() { printf("main\n"); return 0; } would output WinMain, but of course nothing ever works how you expects. Anyways, could somebody please tell me how to get this program to run WinMain first (I do have a reason for using both). I'm running windows 7 with mingw if that helps anything.

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• Sprintf equivalent in Mathematica?

  - by jxy

  I don't know why Wikipedia lists Mathematica as a programming language with printf. I just couldn't find the equivalent in Mathematica. My specific task is to process a list of data files with padded numbers, which I used to do it in bash with fn=$(printf "filename_%05d" $n) The closest function I found in Mathematica is PaddedForm. And after some trial and error, I got it with "filename_" <> PaddedForm[ Round@#, 4, NumberPadding -> {"0", ""} ]& It is very odd that I have to use the number 4 to get the result similar to what I get from "%05d". I don't understand this behavior at all. Can someone explain it to me? And is it the best way to achieve what I used to in bash?

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• Codesample with bufferoverflow (gets method). Why does it not behave as expected?

  - by citronas

  This an extract from an c program that should demonstrate a bufferoverflow. void foo() { char arr[8]; printf(" enter bla bla bla"); gets(arr); printf(" you entered %s\n", arr); } The question was "How many input chars can a user maximal enter without a creating a buffer overflow" My initial answer was 8, because the char-array is 8 bytes long. Although I was pretty certain my answer was correct, I tried a higher amount of chars, and found that the limit of chars that I can enter, before I get a segmentation fault is 11. (Im running this on A VirtualBox Ubuntu) So my question is: Why is it possible to enter 11 chars into that 8 byte array?

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• Handling user input in C

  - by Stuart

  In C, I am writing a program which is taking in user input than comparing it to see which output it should use. I am finding it problomatic and was wondering if someone could give me a hand. So far I have: while(cmd[0] != EOF){ fgets(cmd, sizeof(cmd), stdin); /** Takes in user input and stores it in cmd **/ if(cmd[0] == '\n') printf("%s> ", cwd); else if(strcmp(cmd, "ls") == 0) printf("I will list everything"); } Any ideas? Basically it is just ignoring any user input when there is some. P.S. The variable cwd is just a string.

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• Loop with pointer arithmetic refuse to stay within boundary in C. Gives me segfault.

  - by Fred

  Hi have made this function which is made to replicate an error that I can't get past. It looks like this: void enumerate(double *c, int size){ while(c < &c[size]){ printf("%lf\n", *c); c++; } } I have added some printf's in there and it gives me: Adressof c: 0x100100080, Adressof c + size: 0x1001000a8 I then also print the address of c for each iteration of the loop, it reaches 0x1001000a8 but continues past this point even though the condition should be false as far as I can tell until I get a segfault. If anyone can spot the problem, please tell me, I have been staring at this for a while now. Thanks.

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• Passing a pointer to a function that doesn't match the requirements of the formal parameter

  - by Andreas Grech

  int valid (int x, int y) { return x + y; } int invalid (int x) { return x; } int func (int *f (int, int), int x, int y) { //f is a pointer to a function taking 2 ints and returning an int return f(x, y); } int main () { int val = func(valid, 1, 2), inval = func(invalid, 1, 2); // <- 'invalid' does not match the contract printf("Valid: %d\n", val); printf("Invalid: %d\n", inval); /* Output: * Valid: 3 * Invalid: 1 */ } At the line inval = func(invalid, 1, 2);, why am I not getting a compiler error? If func expects a pointer to a function taking 2 ints and I pass a pointer to a function that takes a single int, why isn't the compiler complaining? Also, since this is happening, what happens to the second parameter y in the invalid function?

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