I have a program (trimmed way down) that compiles and runs as I think it should, yet in the code window an asterisk (operator*) has a red squiggle under it and the mouse-over caption says, 'Error, no operator * matches these operands.' I guess the squiggly line neglected to tell the compiler. The same thing happens if I change operator* to a function named "dot".
If there are few enough hoops to jump through, I would like to report it to MS. But first, tell me if the compiler and I are wrong, and the squiggle is right.
#include <vector>
#include <iostream>
//#include "fp_vectors.h"
// Header file =================
#include <type_traits>
#include <algorithm>
namespace dj {
// Dot-product of two real-valued vectors
template <typename FirstType, typename SecondType>
auto operator*(const FirstType &a, const SecondType &b) -> decltype(a[0]*b[0]){
std::remove_const<decltype(a[0]*b[0])>::type ret = 0.0;
const int sz = std::min(a.size(),b.size());
for(int i=0;i<sz;++i) {
ret += a[i]*b[i];
}
return ret;
}
} // namespace dj
// End header file ================
using namespace std;
typedef vector<float> fvec;
typedef vector<double> dvec;
using namespace dj;
int main()
{
const size_t sz = 3;
fvec fv(sz);
dvec dv(sz);
for(size_t i=0; i<sz; ++i) {
fv[i] = -.89f*(i-1.0f);
dv[i] = 1.6*(i-2.2);
}
double ret = dv*fv; // Earns a red squiggly
cout << ret << endl;
return 0;
}
Bugs in Visual Studio may be reported on Microsoft Connect.
However, I took a brief look at your code, and there are no squiggles in Visual Studio 2012. So, if there was a bug here, it looks like it's been fixed.
Related
Is it possible to put the iterator of list in to set:
I wrote codes as follows :
It failed on VS2015 but run smoothly on g++
And I also tried to use std::hash to calculate a hash value of std::list::iterator
but failed again, it has no hash func for iterator.
And one can help ? Or it's impossible .....
#include <set>
#include <list>
#include <cstring>
#include <cassert>
// like std::less
struct myless
{
typedef std::list<int>::iterator first_argument_type;
typedef std::list<int>::iterator second_argument_type;
typedef bool result_type;
bool operator()(const std::list<int>::iterator& x,const std::list<int>::iterator& y) const
{
return memcmp(&x, &y, sizeof(std::list<int>::iterator)) < 0; // using memcmp
}
};
int main()
{
std::list<int> lst = {1,2,3,4,5};
std::set<std::list<int>::iterator,myless> test;
auto it = lst.begin();
test.insert(it++);
test.insert(it++);
assert(test.find(lst.begin()) != test.end()); // fail on vs 2015
auto it1 = lst.end();
auto it2 = lst.end();
assert(memcmp(&it1,&it2,sizeof(it1)) == 0); // fail on vs 2015
system("pause");
return 0;
}
Yes, you can put std::list<T>::iterator in a std::set, if you tell std::set what order they should be in. A reasonable order could be std::less<T>, i.e. you sort the iterators by the values they point to (obviously you then can't insert an std::list::end iterator). Any other order is also OK.
However, you tried to use memcmp, and that is wrong. The predicate used by set requires that equal values compare equal, and there is no guarantee that equal iterators (as defined by list::iterator::operator==) also compare equal using memcmp.
I find a way to do this as like but not for the end iterator
bool operator<(const T& x, const T& y)
{
return &*x < &*y;
}
Using VS2013, in the C++ code below I get a debug assertion when accessing the vector with an out of range index, which is OK (but the catch block is not reached). When running the release version the program runs without the exception being caught. The output is 1 while it should be 0.
#include <iostream>
#include <vector>
#include <stdexcept>
using namespace std;
vector<int> Vector;
void GetException()
try{
int Sum{ 0 };
// Access an element beyond the end of the vector
for( int i = 0; i <= Vector.size(); i++ )
Sum += Vector[i];
}
catch( ... ){
Vector.clear();
}
int _tmain(int argc, _TCHAR* argv[])
{
Vector.push_back( 1 );
GetException();
cout << Vector.size() << endl;
return 0;
}
When I change it to access a nullptr I get in the debug version an error message for an "unhandled exception" and in the release version it crashes on the access. Are there parameters in VS that modify the behaviour of exceptions?
int Sum{ 0 };
void GetException()
try{
int *pSum{ nullptr };
Sum = *pSum;
}
catch( ... ){
Sum = 1;
}
int _tmain(int argc, _TCHAR* argv[])
{
GetException();
cout << Sum << endl;
return 0;
}
This expression Vector[i] (in your first code example) does not throw exceptions (in normal, release builds anyways), it's simply undefined behavior if i is out of bounds.
This expression Vector.at(i) does throw exceptions (in normal, release builds) if i is out of bounds.
If you want to have a std::vector do bounds checking for you, and throw exceptions if an access is out of bounds, then you should use that form. You can't catch the problem if a Vector[i] access is out of bounds.
I got different results using auto and using Vector when summing two vectors.
My code:
#include "stdafx.h"
#include <iostream>
#include "D:\externals\eigen_3_1_2\include\Eigen\Geometry"
typedef Eigen::Matrix<double, 3, 1> Vector3;
void foo(const Vector3& Ha, volatile int j)
{
const auto resAuto = Ha + Vector3(0.,0.,j * 2.567);
const Vector3 resVector3 = Ha + Vector3(0.,0.,j * 2.567);
std::cout << "resAuto = " << resAuto <<std::endl;
std::cout << "resVector3 = " << resVector3 <<std::endl;
}
int main(int argc, _TCHAR* argv[])
{
Vector3 Ha(-24.9536,-29.3876,65.801);
Vector3 z(0.,0.,2.567);
int j = 7;
foo(Ha,j);
return 0;
}
The results:
resAuto = -24.9536, -29.3876,65.801
resVector3 = -24.9536,-29.3876,83.77
Press any key to continue . . .
I understand that Eigen does internal optimization that generate different results. But it looks like a bug in Eigen and C++11.
The auto keyword tells the compiler to "guess" the best object based on the right hand side of the =. You can check the results by adding
std::cout << typeid(resAuto).name() <<std::endl;
std::cout << typeid(resVector3).name() <<std::endl;
to foo (don't forget to include <typeinfo>).
In this case, after constructing the temporary Vector3, the operator+ method is called, which creates a CwiseBinaryOp object. This object is part of Eigens lazy evaluation (can increase performance). If you want to force eager evaluation (and therefore type determination), you could use
const auto resAuto = (Ha + Vector3(0.,0.,j * 2.567)).eval();
instead of your line in foo.
A few side notes:
Vector3 is identical to the Vector3d class defined in Eigen
You can use #include <Eigen/Core> instead of #include <Eigen/Geometry> to include most of the Eigen headers, plus certain things get defined there that should be.
good afternoon.
I got the code below on a book. I'm trying to execute it, but I don't know what is the "first" and "last" parameters on the MakeCodeWritable function, or where I can find them. Someone can help? This code is about C obfuscation method. I'm using Xcode program and LLVM GCC 4.2 compiler.
#include <stdio.h>
#include <sys/mman.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
typedef unsigned int uint32;
typedef char* caddr_t;
typedef uint32* waddr_t;
#define Tam_celula 64
#define ALIGN __attribute__((aligned(Tam_celula)))
void makeCodeWritable(char* first, char* last) {
char* firstpage = first - ((int)first % getpagesize());
char* lastpage = last - ((int)last % getpagesize());
int pages = (lastpage-firstpage)/getpagesize()+1;
if (mprotect(firstpage,pages*getpagesize(), PROT_READ|PROT_EXEC|PROT_WRITE)==-1) perror("mprotect");
}
void xor(caddr_t from, caddr_t to, int len){
int i;
for(i=0;i<len;i++){
*to ^= *from; from++; to++;
} }
void swap(caddr_t from, caddr_t to, int len){
int i;
for(i=0;i<len;i++){
char t = *from; *from = *to; *to = t; from++; to++;
} }
#define CELLSIZE 64
#define ALIGN asm volatile (".align 64\n");
void P() {
static int firsttime=1; if (firsttime) {
xor(&&cell5,&&cell2,CELLSIZE);
xor(&&cell0,&&cell3,CELLSIZE);
swap(&&cell1,&&cell4,CELLSIZE);
firsttime = 0; }
char* a[] = {&&align0,&&align1,&&align2,&&align3,&&align4,&&align5};
char*next[] ={&&cell0,&&cell1,&&cell2,&&cell3, &&cell4,&&cell5};
goto *next[0];
align0: ALIGN
cell0: printf("SPGM0\n");
xor(&&cell0,&&cell3,3*CELLSIZE);
goto *next[3];
align1: ALIGN
cell1: printf("SPGM2\n"); xor(&&cell0,&&cell3,3*CELLSIZE);
goto *next[4];
align2: ALIGN
cell2: printf("SPGM4\n"); xor(&&cell0,&&cell3,3*CELLSIZE);
goto *next[5];
align3: ALIGN
cell3: printf("SPGM1\n"); xor(&&cell3,&&cell0,3*CELLSIZE);
goto *next[1];
align4: ALIGN
cell4: printf("SPGM3\n"); xor(&&cell3,&&cell0,3*CELLSIZE);
goto *next[2];
align5: ALIGN
cell5: printf("SPGM5\n");
xor(&&cell3,&&cell0,3*CELLSIZE);
}
int main (int argc, char *argv[]) {
makeCodeWritable(...);
P(); P();
}
The first argument should be (char *)P, because it looks like you want to modify code inside function P. The second argument is the ending address of function P. You can first compile the code, and using objdump -d to see the address of beginning and end of P, then calculate the size of the function, SIZE, then manually specify in the makeCodeWritable( (char *)P, ((char *)P) + SIZE.
The second way is utilizing the as to get the size of function P, but it depends on the assembler language on your platform. This is code snipe I modified from your code, it should be able to compile and run in x86, x86_64 in GCC 4.x on Linux platform.
align5: ALIGN
cell5: printf("SPGM5\n");
xor(&&cell3,&&cell0,3*CELLSIZE);
// adding an label to the end of function P to assembly code
asm ("END_P: \n");
;
}
extern char __sizeof__myfunc[];
int main (int argc, char *argv[]) {
// calculate the code size, ending - starting address of P
asm (" __sizeof__myfunc = END_P-P \n");
// you can see the code size of P
printf("code size is %d\n", (unsigned)__sizeof__myfunc);
makeCodeWritable( (char*)P, ((char *)P) + (unsigned)__sizeof__myfunc);
P(); P();
}
With some modification to support LLVM GCC and as in Mac OS X
int main (int argc, char *argv[]) {
size_t sizeof__myfunc = 0;
asm volatile ("movq $(_END_P - _P),%0;"
: "=r" (sizeof__myfunc)
: );
printf("%d\n", sizeof__myfunc);
Need Help.I'm stuck at a problem when running a C++ code on Windows- Visual Studio.
When I run that code in Linux environment, there is no restriction on the memory I am able to allocate dynamically(till the size available in RAM).
But on VS Compiler, it does not let me create an array beyond a limited size.
I've tried /F option and 20-25 of google links to increase memory size but they dont seem to help much.
I am currently able to assign only around 100mb out of 3gb available.
If there is a solution for this in Windows and not in Visual Studio's compiler, I will be glad to hear that as I have a CUDA TeslaC2070 card which is proving to be pretty useless on Windows as I wanted to run my CUDA/C++ code on Windows environment.
Here's my code. it fails when LENGTH>128(no of images 640x480pngs. less than 0.5mb each. I've also calculated the approximate memory size it takes by counting data structures and types used in OpenCV and by me but still it is very less than 2gb). stackoverflow exception. Same with dynamic allocation. I've already maximized the heap and stack sizes.
#include "stdafx.h"
#include <cv.h>
#include <cxcore.h>
#include <highgui.h>
#include <cuda.h>
#include "cuda_runtime.h"
#include "device_launch_parameters.h"
#define LENGTH 100
#define SIZE1 640
#define SIZE2 480
#include <iostream>
using namespace std;
__global__ void square_array(double *img1_d, long N)
{
int idx = blockIdx.x * blockDim.x + threadIdx.x;
img1_d[idx]= 255.0-img1_d[idx];
}
int _tmain(int argc, _TCHAR* argv[])
{
IplImage *img1[LENGTH];
// Open the file.
for(int i=0;i<LENGTH;i++)
{ img1[i] = cvLoadImage("abstract3.jpg");}
CvMat *mat1[LENGTH];
for(int i=0;i<LENGTH;i++)
{
mat1[i] = cvCreateMat(img1[i]->height,img1[i]->width,CV_32FC3 );
cvConvert( img1[i], mat1[i] );
}
double a[LENGTH][2*SIZE1][SIZE2][3];
for(int m=0;m<LENGTH;m++)
{
for(int i=0;i<SIZE1;i++)
{
for(int j=0;j<SIZE2;j++)
{
CvScalar scal = cvGet2D( mat1[m],j,i);
a[m][i][j][0] = scal.val[0];
a[m][i][j][1] = scal.val[1];
a[m][i][j][2] = scal.val[2];
a[m][i+SIZE1][j][0] = scal.val[0];
a[m][i+SIZE1][j][1] = scal.val[1];
a[m][i+SIZE1][j][2] = scal.val[2];
}
} }
//cuda
double *a_d;
int N=LENGTH*2*SIZE1*SIZE2*3;
cudaMalloc((void **) &a_d, N*sizeof(double));
cudaMemcpy(a_d, a, N*sizeof(double), cudaMemcpyHostToDevice);
int block_size = 370;
int n_blocks = N/block_size + (N%block_size == 0 ? 0:1);
cout<<n_blocks<<block_size;
square_array <<< n_blocks, block_size >>> (a_d, N);
cudaMemcpy(a, a_d, N*sizeof(double), cudaMemcpyDeviceToHost);
//cuda end
char name[]= "Image: 00000";
name[12]='\0';
int x=0,y=0;
for(int m=0;m<LENGTH;m++)
{
for (int i = 0; i < img1[m]->width*img1[m]->height*3; i+=3)
{
img1[m]->imageData[i]= a[m][x][y][0];
img1[m]->imageData[i+1]= a[m][x][y][1];
img1[m]->imageData[i+2]= a[m][x][y][2];
if(x==SIZE1)
{
x=0;
y++;
}
x++;
}
switch(name[11])
{
case '9': switch(name[10])
{
case '9':
switch(name[9])
{
case '9': name[11]='0';name[10]='0';name[9]='0';name[8]++;
break;
default : name[11]='0';
name[10]='0';
name[9]++;
}break;
default : name[11]='0'; name[10]++;break;
}
break;
default : name[11]++;break;
}
// Display the image.
cvNamedWindow(name, CV_WINDOW_AUTOSIZE);
cvShowImage(name,img1);
//cvSaveImage(name ,img1);
}
// Wait for the user to press a key in the GUI window.
cvWaitKey(0);
// Free the resources.
//cvDestroyWindow(x);
//cvReleaseImage(&img1);
//cvDestroyWindow("Image:");
//cvReleaseImage(&img2);
return 0;
}
The problem is that you are allocating a huge multidimensional array on the stack in your main function (double a[..][..][..]). Do not allocate this much memory on the stack. Use malloc/new to allocate on the heap.