Questions tagged [macros]
***DO NOT USE for VBA / MS-Office languages. Use [vba] instead.*** A macro is a rule or pattern that specifies how a certain input sequence (often a sequence of characters) should be mapped to an output sequence (also often a sequence of characters) according to a defined procedure.
macros
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How can you compare two character strings statically at compile time
I would like to create a macro which can compare 2 strings, and emit a compile time error if the condition isn't met. This could be though of as a compile time assertion.
I'm not sure how I could do ...
- 15k
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votes
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C Macro Question -(x) vs (-x)
I'm going through quiz answers from my professor and a question was:
the correct implementation of a function like macro for absolute value is:
#define abs(x) ((x)<0 ? (-x) : (x))
#define abs(x) ...
- 28.9k
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votes
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multiple arity in defmacro of clojure
I encountered a strange problem relating to defmacro in Clojure, I have code like
(defmacro ttt
([] (ttt 1))
([a] (ttt a 2))
([a b] (ttt a b 3))
([a b c] `(println ~a ~b ~c)))
and I run with ...
- 800
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Too many arguments provided to function-like macro invocation [duplicate]
Say we have an implementation of std::aligned_storage. I've defined two macros for the alignof and alignas operators.
#include <iostream>
#include <cstddef>
#define ALIGNOF(x) alignof(x)
...
- 10.3k
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votes
2
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Clojure defmacro loses metadata
I am trying to create a little Clojure macro that defs a String with a type hint:
(defmacro def-string [name value]
`(def ^String ~name ~value))
(def-string db-host-option "db-host")
When I ...
- 32k
25
votes
1
answer
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C strange macro syntax
I found this C code example, and I am absolutely puzzled:
#include <stdio.h>
#define M(a,b) a%:%:b
main()
{
int a=1, b=2, ab[]={10,20}, c;
printf( "%d", M(a,b)<:a:> );
printf( "%d",...
- 4,541
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How do I create a Rust macro with optional parameters using repetitions?
I'm currently looking into Rust macros and I can not find any detailed documentation on repetitions. I would like to create macros with optional parameters. This would be my idea:
macro_rules! ...
- 3,209
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7
answers
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Is it OK to use a code block as an argument for a C macro?
I have a pattern that is basically some boilerplate code with a part that varies in the middle
if(condition){
struct Foo m = start_stuff();
{ m.foo = bar(1,2); m.baz = 17; } //this part ...
- 69.1k
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What is the reason for having unreserved identifiers as built-in macros in gcc?
Today I stumbled upon a rather interesting compiler error:
int main() {
int const unix = 0; // error-line
return unix;
}
Gives the following message with gcc 4.3.2 (yes, ancient...):
error: ...
- 293k
24
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3
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C++ macro '##' doesn't work after '->' operator
I have a shared_ptr object x, which has get and set methods as follows:
x->a_value();
x->set_a_value();
x->b_value();
x->set_b_value();
When i try to define a macro:
#define MAC(...
- 659
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votes
9
answers
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Best AutoHotKey macros? [closed]
I use AutoHotKey for Windows macros. Most commonly I use it to define hotkeys that start/focus particular apps, and one to send an instant email message into my ToDo list. I also have an emergency ...
- 241
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6
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Vim - Find pattern on currently line ONLY
I'm wondering if there is a way to find a pattern, but restrict it to the current line. Basically, the equivalent of /PATTERN but restricted to the current line, rather than the entire document.
I've ...
- 437
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2
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how to implement macros in Go?
I've project done in C++ where I used #define macros to give a name of the project, which I used in several places, I don't change this name often but sometimes I may need to change this, then I ...
- 465
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Generating an error if checked boolean macro is not defined
I have several configuration files each one containing the definition of some boolean macro, to be set to 0 or 1. Then, in my code, I check the value of such a macro to decide which part of the code ...
- 19.8k
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Linux Kernel's __is_constexpr Macro
How does the __is_constexpr(x) macro of the Linux Kernel work? What is its purpose? When was it introduced? Why was it introduced?
/*
* This returns a constant expression while determining if an ...
- 25.6k
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Racket vs Scheme macros
Do racket macros have more advanced functionality than those found in Scheme or Common Lisp? I suspect so, especially regarding modules, namespaces and scoping, etc, but I'd appreciate a simple ...
- 37.9k
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votes
2
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Difference between #pragma and _Pragma() in C
What is the difference between #pragma and _Pragma() in C?
syntax:
#pragma arg
and
_Pragma(arg)
When should I use _Pragma(arg)?
- 4,863
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How do I show the value of a #define at compile time in gcc
So far I've got as far as:
#define ADEFINE "23"
#pragma message ("ADEFINE" ADEFINE)
Which works, but what if ADEFINE isn't a string?
#define ADEFINE 23
#pragma message ("ADEFINE" ADEFINE)
causes:
...
- 17.3k
24
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2
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C macros and use of arguments in parentheses
Example
#define Echo(a) a
#define Echo(a) (a)
I realize there probably isn’t a significant difference here, but why would you ever want to include the a within parenthesis inside the macro body? ...
- 7,209
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MSBuild.exe not accepting either /p:DefineConstants nor /p:PreprocessorDefinitions
I've been through quite a number of articles on Stack Overflow that answered the question "How do I pass preprocessor definitions to the compiler from the MSBuild command line," and they all responded ...
- 11.7k
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What is EXPORT_SYMBOL_GPL in Linux kernel code?
What is EXPORT_SYMBOL_GPL in Linux kernel code?
Below is a piece of code, which contains EXPORT_SYMBOL_GPL
62 struct resource *platform_get_resource(struct platform_device *dev,
63 ...
- 7,653
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Recording a 'macro'? or a series of actions in Visual Studio Code?
I would need something like this. Once I create a folder within a project. A React Project for example. I could select that folder and run some kind of macro or series of actions that would do this.
...
- 1,666
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7
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Why are C macros not type-safe?
If have encountered this claim multiple times and can't figure out what it is supposed to mean. Since the resulting code is compiled using a regular C compiler it will end up being type checked just ...
- 6,802
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2
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Is there a #define for C99?
I want to do something in C99 one way, otherwise to perform it another way. What is the #define to check for?
#ifdef C99
...
#else
...
#endif
- 1,076
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How can I generate unique values in the C preprocessor?
I'm writing a bunch of related preprocessor macros, one of which generates labels which the other one jumps to. I use them in this fashion:
MAKE_FUNNY_JUMPING_LOOP(
MAKE_LABEL();
MAKE_LABEL();
)
...
- 22.7k
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votes
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What predefined macro can I use to detect the target architecture in Clang?
I would like to write code depending on whether the target architecture is e.g. armv7, armv7s, or arm64.
The reason that I can't use sysctlbyname is that this would give me the underlying ...
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Is it possible to implement Common Lisp's macro system in scheme?
Hopefully this is not a redundant question.
As a newcomer to scheme I am aware that syntax-case macros are more powerful than the syntax-rules alternative, at the cost of unwanted complexity.
Is ...
- 2,125
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Is there a way to get the field names of a struct in a macro?
Consider the following example:
struct S {
a: String,
b: String,
}
I have a macro which is called like this:
my_macro!(S);
I want to access the field names of the struct in the macro like ...
- 395
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How do I define preprocessor macros in Xcode 4?
I have two targets set up for my app (a lite version and a pro version) and I want to integrate some subtle differences in the code for each of them (e.g. the pro version will not show any iAd banners)...
user843337
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How can I access template variable in TWIG macro?
I'm not able to access template variable in TWIG macro.
Here is a simplified example:
{% set myname = "Ligio" %}
{{ _self.pagedurl(1) }}
{% macro pagedurl(page) %}
Hi {{ _self.myname }}! This ...
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How to tame the Windows headers (useful defines)?
In one of the answers to this question jalf spoke about useful define NOMINMAX, that could prevent from unwanted defining min/max macros. Are there other useful defines that can help to control ...
- 98.4k
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Compile-time string encryption
I don't want reverse-engineers to read the plain-text of hardcoded strings in my application. The trivial solution for this is using a simple XOR-Encryption. The problem is I need a converter and in ...
- 1,181
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How do you compile macros in a Lisp compiler?
In a Lisp interpreter, there can easily be a branch in eval that can expand a macro, and in the process of expanding it, call functions to build up the expanded expression. I've done this before using ...
- 2,641
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Understanding DEFER and OBSTRUCT macros
I created a small macro metaprogramming library that implements basic useful constructs such as REPEAT(times, x), IF(value, true, false), tuples, and more.
Most of my implementations work by ...
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What's the Swift equivalent of Objective-C's "#ifdef __IPHONE_11_0"?
I want to use Xcode 9 to add iOS 11 code to my project while keeping the option to compile the project with Xcode 8 which only supports iOS 10.
In Objective-C I can do this by using a preprocessor ...
- 90.1k
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How to debug macros efficiently in VS?
I've got a pretty complicated macro inside my (unmanaged) C++ code. Is there any way to expand macros in VS debugger? Or maybe there is another way to debug macros there?
F.e. I'd like to place a ...
- 41.5k
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Generate include file name in a macro
I'm trying to generate include file name in macro. This is supposed to be legal in C++:
#define INCLUDE_FILE "module_impl_win.hpp"
#include INCLUDE_FILE
this works fine, but as soon as I try to ...
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What does ##__VA_ARGS__ mean?
I would like to know what ## does in this macro definition:
#define debug(M, ...) fprintf(stderr,M "\n",##__VA_ARGS __)
I googled for an answer and I came up with the following.
The ## will remove ...
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How to delete all comments in a selected code section?
Every once in a while, my code gets littered with many useless comments, most of them are obsolete lines of code, and some are obsolete "memos to self".
So I was wondering if there's a way to just ...
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How can I use the format! macro in a no_std environment?
How could I implement the following example without using std?
let text = format!("example {:.1} test {:x} words {}", num1, num2, num3);
text has type &str and num1, num2 and num3 have any ...
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How to remove the enclosing parentheses with macro?
No comma is allowed in a macro argument because it will be treated as more than one arguments and the preprocessing will be wrong. However, we can parenthesize the argument to let preprocessor treat ...
- 13.4k
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How to prevent macro redefinition
After working some time on my project, this warning begins to appear:
2>Game.cpp
2>c:\program files\microsoft sdks\windows\v6.0a\include\windef.h(126) : warning C4005: 'APIENTRY' : redefinición ...
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How to import macros in Rust?
I'm struggling with how to import macros from an external crate. In my main.rs I'm importing the Glium crate:
#![macro_use]
extern crate glium;
pub use glium::*;
// where my actual main function ...
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How do I stop running Vim macro
I recorded a macro to a register and started it with too many repetitions. It takes way to much time to complete each macro.
How do I cancel/stop Vim executing macro? Is there a way by doing it ...
- 401
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How do I avoid name collision with macros defined in Windows header files?
I have some C++ code that includes a method called CreateDirectory(). Previously the code only used STL and Boost, but I recently had to include <windows.h> so I could look-up ...
- 6,060
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Generating Clojure code with macro containing type hints
I'm trying to generate some Clojure code with type hints, however the type hints seem to disappear whenever I build some code (they also don't function when the code is compiled)
e.g.
`(let [^...
- 106k
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How do I define a macro with multiple pragmas for Clang?
I'd like to add some macros to ease (un)setting a specific warning around routines that we are deprecating internally.
I'd like to turn this:
#pragma clang diagnostic push
#pragma clang diagnostic ...
- 35.8k
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votes
4
answers
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List of the $(xxx) macro in visual studio
I would like to establish a list of all the visual studio macro that can be used in the post-build event script.
$(Configuration) : Name of the current build configuration (ie: Debug or Release).
- 11.6k
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Incompatible pointer types passing in _Generic macro
The following code generates 2 warnings which are described in the question's title.
#include <stdio.h>
static void _print_f(float *f){printf("float : %f\n", *f);}
static void _print_i(int *i) ...
- 11.9k