The cost of opening a file, discarding all its contents, and closing it over and over might not sound like much, but for a large header included transitively by hundreds of other headers (e.g. windows.h, the low-level stuff providing simple type definitions like stdint.h, types.h, etc.), the difference between opening it exactly once per source file and opening it a hundred times …

Aug 25, 2008 · Aside from the form of stack overflow that you get from a direct recursion (eg Fibonacci(1000000)), a more subtle form of it that I have experienced many times is an indirect recursion, where a function calls another function, which calls another, and then one of those functions calls the first one again.

Nov 27, 2015 · In the normal C or C++ build process the first thing that happens is that the PreProcessor runs, the preprocessor looks though the source files for preprocessor directives like #define or #include and then performs simple operations with them. in the case of a #define directive the preprocessor does simple text based substitution.

Jul 9, 2018 · #define is part of something called the "preprocessor." Essentially, this is the code that is processed before the C document is compiled. Most of the preprocessor code is in a file with a ".h" extension (which is why you may have seen that when importing libraries). The preprocessor language is primitive.

Dec 29, 2023 · @ThomasWeller: n3690 says "Unsigned integers shall obey the laws of arithmetic modulo 2^n where n is the number of bits in the value representation of that particular size of integer" and as a note "This implies that unsigned arithmetic does not overflow because a result that cannot be represented by the resulting unsigned integer type is reduced modulo the …

Oct 28, 2009 · #define is a compiler pre processor directive and should be used as such, for conditional compilation etc.. E.g. where low level code needs to define some possible alternative data structures for portability to specif hardware. It can produce inconsistent results depending on the order your modules are compiled and linked.

Mar 28, 2018 · Note that #define fori(x) for (int i=0; i<=x; i++) should be written #define fori(x) for (int i=0; i<=(x); i++) instead. (Note the additional brackets.) (Note the additional brackets.) The use of brackets may not be obvious in this example, but something wrong will happen if someone put a bitwise operation in argument x.

Dec 21, 2011 · #define VALUE 4 int main() { const int x = VALUE; return 0; } I use gcc and cpp ( the C preprocessor ) for the examples, but you can probably do this with whatever compiler suite you have, with different flags, of course.

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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.