C++ :: Macro To Template?
Mar 22, 2013
I have this macro, that expands to some methods of my class:
Code:
#define POPULAR_COMBO_FILTRO_COM_BASE(classeTabela)
void VisualizadorLogsFrame::PopularComboFiltroCom ## classeTabela (bool limparTexto) {
long from, to;
m_cbxDetalhe->GetSelection(&from, &to);
[Code]...
but I get a compile error on this line:
Code:
for (list< CLASSE_TABELA *>::iterator linha = lista->begin(); linha != lista->end(); linha++) {
what am I doing wrong ? the error is:
VisualizadorLogsMain.h:174: error: expected ';' before 'linha'
VisualizadorLogsMain.h:174: error: 'linha' was not declared in this scope
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Feb 26, 2012
Is it possible to define a macro with in a macro? Any trick will do. I am trying to do quick conversion of cuda program to open mp by defining some macros at the top:
Code:
#define __syncthreads() #pragma omp barrier
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Jan 4, 2015
I am trying to create a small set of filepath functions that I intend to compile across linux and windows (I prefer not to use a big library). I want to have a global constant PATH_SEPARATOR that depends on the OS environment. This is what I set at the top of header file.
Code:
#include <stdio.h>
const char PATH_SEPARATOR =
#ifdef _WIN32
'';
#else
'/';
#endif I was hoping to test this while compiling this in a linux environment using gcc, thusly:
Code:
int main (int argc, char const* argv[])
}
[code]....
where apparently, I seem not to be able to "set" a part of the code to have "_WIN32" defined. I don't know if I explained this clearly.
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Sep 12, 2013
I'm doing right now is creating a function that callocs (I prefer this to malloc) and returns a string, and it will work similar to printf, I'm calling the function alloCpy(),I have several values that I need in a malloced string, so I call Code: myAllocedString = alloCpy("Value 1 is %s, value 2 is %s, and value 3 is %d", str1, str2, num); To do this I'm using the Variadic Macro, the reason I'm not just using a Variadic Function such as this: Code: char* alloCpy(char *format, ...) {} is because I need to append NULL to the end for the sake of looping through arguments, and I'm understanding it thusfar, but I have a few issues, first of all, I tried defining the Macro in a header file, but when I try to call it I get the error "Undefined reference to alloCpy". Also, to loop through arguments to get string lengths I'm using va_arg(args, char*) which requires all the arguments to be of type char*. Here is my code:
myheader.h:
Code:
#define alloCpy(format, ...) _alloCpy(format, ##__VA_ARGS__, NULL);
char* _alloCpy(char *format, ...); mycfile.c: Code: char* _alloCpy(char *format, ...) {
va_list args;
va_start(args, format);
int args_len = 0;
}
[code]....
So, how can I do this to, first of all, make my macro function accessible from other files importing myheader.h, and second, how can I make it accept any type of argument like printf, so that my example above would work?
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Jan 16, 2015
Say I have something lke
Code:
#define FOO BAR
#if FOO == BAR
doX();
#else
doY();
#endif
This causes doX(); to be executed. But the intent is to have doY(); be run. I'm guessing this is because BAR is undefined and therefore blank, so blank equals blank. Is there some way to compare the symbol FOO was set to instead of its value, BAR?
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Apr 4, 2013
I heard that const shall be preferred over #define . So I start to change my program accordingly.
But then below error message occurs during compilation:
#include "common.h"
#include "definition.h"
#include "particle.h"
int main() {
Particle *p = new Particle();
[Code] .....
I guess the error occurs because, when the line 9 of particle.h (File 4) is compiled, value of const int dimension is not seen by the compiler.
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Jun 12, 2014
I have to migrate C++ source which is compiled with MinGW-gcc to be compiled with VS2013, and have one issue with one macro used for serialization.
Here is macro:
#define IMPLEMENT_SERIALIZE(statements)
unsigned int GetSerializeSize(int nType, int nVersion) const
{
CSerActionGetSerializeSize ser_action;
const bool fGetSize = true;
[Code] ....
Here is place in code were it is call (in class declaration):
IMPLEMENT_SERIALIZE(({
if (!fRead) {
uint64 nVal = CompressAmount(txout.nValue);
READWRITE(VARINT(nVal));
[Code] .....
When compile received errors:
main.h(555): error C2059: syntax error : '{'
main.h(555): error C2143: syntax error : missing ';' before '{'
line 555 is end of macro call ( "})").
How should look using of this macro in order to avoid that errors?
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Dec 29, 2013
"If you examine the expansion of max, you will notice some pitfalls. The expressions are evaluated twice; this is bad if they involve side effects like increment operators or input and output. For instance, the below example will increment the larger twice."
#define max(A, B) ((A) > (B) ? (A) : (B))
max(i++, j++)/* WRONG */
I don't see what the problem is with the code above. i is incremented and j is incremented and then it performs a ternary operation to see which is greater. Am I missing something?
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Jun 27, 2012
Say I have two projects A and B. A depends on B. If project A defines a macro to be 100 and project B defines the same macro to be 200. In project A, if I use this macro, what value would this macro be? Let's just forget macro is evil for the time being. Let's also forget that it is not good to define the same macro twice for the time being.
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Dec 5, 2013
I'm trying to implement a simple template array class, but when i came into the operator< i actually have to use a template :
my code is something like :
template<typename _Type, std::size_t _Size>
class array {
public :
[Code] ......
but i am having an error of shadows template param 'class _Type' is it w/ the name conflict between the array template parameter and the function template parameter ?
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Nov 6, 2013
Error1error C2955: 'DoubleLinkedListInterface' : use of class template requires template argument listdoublelinkedlist.h10
Error2error C2244: 'DoubleLinkedList<T>::DoubleLinkedList' : unable to match function definition to an existing declaration doublelinkedlist.cpp7
Error3 .cpperror C2244: 'DoubleLinkedList<T>::~DoubleLinkedList' : unable to match function definition to an existing declaration 12
.h
#pragma once
#include "DoubleLinkedListInterface.h"
#include "Node.h"
#include <iostream>
[Code]....
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Nov 15, 2014
when i was finding a way to concatenate three integers in C, I came across a snippet like this
Code:
#include<stdio.h>
#define cat(a,b,c) a##b##c
int main()
{
int d;
d=cat(1,2,3);
return 0;
}
How the macro works here? I am unable to understand the function '#' plays in the macro.
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Apr 24, 2014
I need writing a macro that would return true/false (1/0) )value. I want to check if a certain element exists in the array. The macro will accept array, its size, and the value to be compared, and must return yes or no. Here is the code that I have written:
Code:
#define EXISTS(T, a, n, val) do {
char ret=0;
T *a_ = (a);
size_t n_ = (n);
for (; n_ > 0; --n_, ++a_){
ret = (*a_ == val);
}
}
while(0)
How can I get the result from this macro.
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Nov 22, 2013
I'm trying building a new macro for change the array size:
#define redim(varname,x) ((sizeof(varname)*) realloc (varname, x * sizeof(varname)));
int b;
redim(b,3);
error message:
"error: expected primary-expression before ')' token"
what isn't right with these macro?
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Jul 16, 2014
I have built a static library that contains a macro. From a separate exe, I am calling this macro, but it doesn't work.
The compilation of the static library and that of the exe went okay.
Static lib contains just the macro definition.
Exe contains call to this macro.
Is there anything else that I need to do for this to work?
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Jan 20, 2014
i would like to know if its possible to use a c# command to attach a macro ( JitBix MacroRecorder ) so it would send keystrokes while the process/program was minimized. i've tried with [lapeiro, on 20 January 2014 - 06:43 AM, said: i would like to know if its possible to use a c# command to attach a macro ( JitBix MacroRecorder ) so it would send keystrokes while the process/program was minimized.
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Dec 30, 2013
The book uses this example:
#define ALLOCSIZE 10000 /* size of available space */
static char allocbuf[ALLOCSIZE]; /* storage for alloc */
static char *allocp = allocbuf; /* next free position */
char *alloc(int n)
/* return pointer to n characters */
[Code] ....
The logic here I don't understand:
if (allocbuf + ALLOCSIZE - allocp >= n)
allocbuf is a char array allocated with 10000 positions. We add that to ALLOCSIZE macro which is 10000. Does that return a value of 20000? If so, it doesn't make sense to do this because all we had to do was this:
if (allocbuf - allocp >= n)
That takes length of allocbuf which is 10000 and subtracts allocp from it. So if allocp is 1000 we are left with 9000 available slots. And we can use that to check if we have enough to allocate n elements.
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Nov 30, 2012
I'm trying to build libglib using MSVC. libglib doesn't use dllexport - so to create usable DLLs it needs to generate a .DEF file. It does this by using a .symbols file. Here's a cut-down example:-
Code:
/* This file lists all exported symbols. It is used to generate the glib.def file used to control exports on Windows.*/
/* glib.symbols */
g_mkdir_with_parents
#ifdef G_OS_WIN32
g_file_get_contents_utf8
#endif
The following commands would produce the following files called glib.def
Code:
cl /EP glib.symbols > glib.def
produces this in glib.def:-
g_mkdir_with_parents
Code:
whereas this:-
cl /EP -DG_OS_WIN32 glib.symbols > glib.def
produces this in glib.def:-
g_mkdir_with_parents
g_file_get_contents_utf8
So this is a handy way of producing conditional .DEF files. Fortunately, this can all be built into a Visual Studio macro in my vsprops file - e.g.
Code:
<UserMacro
Name="GlibGenerateGlibDef"
Value="echo >"$(SolutionDir)glib.def" && cl /EP -DG_OS_WIN32 glib.symbols >>"$(SolutionDir)glib.def""
/>
Problem:- Although I can run the macro as a pre-build step (and it does produce conditional entries in the generated .DEF file) it DOESN'T produce the word EXPORTS at the top of the file. So the linker then fails to recognise it as a valid .DEF file.
How can I add that word EXPORTS to the top of the generated file? I tried just adding EXPORTS to the top of the symbols file but that didn't work. I also tried this variation on the macro:-
Code:
Name="GlibGenerateGlibDef"
Value="echo EXPORTS >"$(SolutionDir)glib.def" && cl /EP -DG_OS_WIN32 glib.symbols
But that didn't work either I feel sure there must be a way to do this.
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Aug 14, 2013
It's common to see the following macros:
Code:
#define DEBUG_NEW new(__FILE__, __LINE__)
#define new DEBUG_NEW
and overloading operator new for debugging purposes. It usually works but there is a problem when use operator new syntax in code instead of directly use new. I can change my code but i can't change third party's code. Something like this:
Code:
int* j = static_cast<int*>(::operator new(sizeof(int)));
It's not common, but it appears occassionally.With that syntax, new macro generates compilation errors.
Is there any way to fix this problem?
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Oct 22, 2014
In the following example, SET_DARKENING_PARAMETERS_0 is a fairly simple macro which accepts 9 parameters. The first one is called driver and the other 8 are all ints. Basically, the 8 x ints get assigned to the first 8 elements of an array which is owned by driver. I can call the macro successfully if I do this:-
Code: SET_DARKENING_PARAMETERS_0 ( some_driver, 500, 400, 1000, 275, 1667, 275, 2333, 0 );
But in the actual code I'm trying to compile, the 8 x ints are themselves encoded into a secondary macro like this:-
Code: #define CONFIG_OPTION_DARKENING_PARAMETERS 500, 400, 1000, 275, 1667, 275, 2333, 0
So the actual code (to call SET_DARKENING_PARAMETERS_0) looks like this:-
Code: SET_DARKENING_PARAMETERS_0 ( some_driver, CONFIG_OPTION_DARKENING_PARAMETERS );
But the two combined macros won't compile with VC8. Basically, I get warning #C4003 (not enough parameters for macro 'SET_DARKENING_PARAMETERS_0') followed by a load of syntax errors. However, the code (allegedly) compiles with gcc.
I'm wondering if macro CONFIG_OPTION_DARKENING_PARAMETERS might be getting truncated to just 500, (with the following parameters getting ignored)?
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May 11, 2013
Just wandering, will something like this work? header
Code:
#define func(arg) func_(arg) ...
static void func_(arg); code Code: #include "header"
int main()
{
func(arg);
}
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Jul 23, 2014
I thought I'd display my fun use of the new C++11 auto keyword to create a compile time foreach. It only works for STL collections, or anything that implements the STL collection iterator methods begin(), end() that return a STL iterator.
// Standard Template Library foreach
// element = iterator name
// collection = STL data collection variable
#define stl_foreach(element, collection)
for(auto element = collection.begin(), __end__ = collection.end();
element != __end__; element++)
}
[code]....
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May 27, 2013
I have a generic template class with another template in one of its types. Now I want to specialize one of its methods for a particular (template) class, which leads to a compile error, however.
Here is the example:
#include <stdio.h>
template<typename Type>
class Obj1 {
public:
void ID() { printf("Object 1, size = %zu
[Code] .....
GCC ends with:
:35:27: error: type/value mismatch at argument 2 in template parameter list for ‘template<class Type, template<class> class O> class Foo’
:35:27: error: expected a class template, got ‘Obj2<Type>’
What is wrong with the specialization? Can it even be achieved and how (if so)?
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Nov 2, 2014
how I want the code to look. Only problem is it doesn't work (Line 11). I have some experience with templates but I'm not a pro.
Basically I want the "Channels<3>" to be a type that I can use to specify a Cable with similar to vector<float/int> it would be Cable<Channels<2 or 3>>.
What have I messed up with the syntax?
#include <iostream>
#include <vector>
using namespace std;
[Code].....
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Mar 14, 2014
I have a function:
template<class Iterator, class T>
void a(Iterator, Iterator, const T&);
and I want to be able to simplify calls to 'a' with calls like
a(someIteratableContainer);
instead of having to call:
a(someIteratableContainer.begin(), someIteratableContainer.end(), valueOfTheContainersElementType);
I also want to be able to generalize the function to handle any of the standard iteratable contains: array, vector, deque, whatever.
I was under the impression I could write:
template<template<class T> class U> a(U<T>& container) {
a(container.begin(), container.end(), g(T()));
}
where 'g()' returns an object of the element type. However, the compiler is claiming, no matter how I write a call to the overload, the original template is selected and/or the overload is invalid, depending on the various ways I attempt to write said overload.
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Jul 13, 2014
How to write a function macro in C for finding the sqrt of a number?
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