Define Status Quo Ante

The subject of define status quo ante encompasses a wide range of important elements. c++ - What does ## in a #define mean? 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.

From another angle, what is the scope of a #define? I have a question regarding the scope of a #define for C/C++ and am trying to bet understand the preprocessor. Let's say I have a project containing multiple sour... 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 ... 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...

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... Moreover, 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: How do I show the value of a #define at compile-time?. I know that this is a long time after the original query, but this may still be useful. It's important to note that, this can be done in GCC using the stringify operator "#", but it requires two additional stages to be defined first. #define XSTR(x) STR(x) #define STR(x) #x The value of a macro can then be displayed with: #pragma message "The value of ABC: " XSTR(ABC) See: 3.4 Stringification in the gcc online ... c# - How do you use #define?

8 #define is used to define compile-time constants that you can use with #if to include or exclude bits of code. Additionally, c - How do I concatenate #define value? You'll need to complete a few actions and gain 15 reputation points before being able to upvote.

Upvoting indicates when questions and answers are useful. What's reputation and how do I get it? Instead, you can save this post to reference later. c++ - Declaring a function using #define - Stack Overflow.