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- Is it possible to use a if statement inside #define?
As far as I know, what you're trying to do (use if statement and then return a value from a macro) isn't possible in ISO C but it is somewhat possible with statement expressions (GNU extension) Since #define s are essentially just fancy text find-and-replace, you have to be really careful about how they're expanded I've found that this works on gcc and clang by default:
- c++ - What does ## in a #define mean? - Stack Overflow
In other words, when the compiler starts building your code, no #define statements or anything like that is left A good way to understand what the preprocessor does to your code is to get hold of the preprocessed output and look at it
- c++ - Why use #define instead of a variable - Stack Overflow
What is the point of #define in C++? I've only seen examples where it's used in place of a "magic number" but I don't see the point in just giving that value to a variable instead
- Why are #ifndef and #define used in C++ header files?
I have been seeing code like this usually in the start of header files: #ifndef HEADERFILE_H #define HEADERFILE_H And at the end of the file is #endif What is the purpose of this?
- Difference between `constexpr` and `#define` - Stack Overflow
So I read the interesting answers about what are the differences between constexpr and const but I was curious about are the differences between #define and constexpr ? I feel like constexpr is jus
- c preprocessor - Is there a good reason for always enclosing a define . . .
#define _add_penguin(a) penguin ## a #define add_penguin(a) _add_penguin(a) #define WIDTH (100) #define HEIGHT 200 add_penguin(HEIGHT) expands to penguin200 add_penguin(WIDTH) error, cannot concatenate penguin and (100) Same for stringization (#) Clearly this is a corner case and probably doesn't matter considering how WIDTH will presumably be used Still, it is something to keep in
- What is the difference between #define and const? [duplicate]
The #define directive is a preprocessor directive; the preprocessor replaces those macros by their body before the compiler even sees it Think of it as an automatic search and replace of your source code A const variable declaration declares an actual variable in the language, which you can use well, like a real variable: take its address, pass it around, use it, cast convert it, etc Oh
- debugging - Can you #define a comment in C? - Stack Overflow
I'm trying to do a debug system but it seems not to work What I wanted to accomplish is something like this: #ifndef DEBUG #define printd #else #define printd printf #endif Is there a
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