The only ‘standard’ thing about NDEBUG is that it’s used to control whether the assert macro will expand into something that performs a check or not. MSVC helpfully defines this macro in release build configurations by defining it in the project for you. You can change that manually by editing the project configuration. Other toolchains … Read more
C99 says (§6.4.7/3): If the characters ‘, \, “, //, or /* occur in the sequence between the < and > delimiters, the behavior is undefined. Similarly, if the characters ‘, \, //, or /* occur in the sequence between the ” delimiters, the behavior is undefined. (footnote: Thus, sequences of characters that resemble escape … Read more
This article answers your question: C/C++ tip: How to detect the operating system type using compiler predefined macros (plus archive.org link in case it vanishes). The article is quite long, and includes tables that are hard to reproduce, but here’s the essence: You can detect Unix-style OS with: #if !defined(_WIN32) && (defined(__unix__) || defined(__unix) || … Read more
He who is Shy* gave you the germ of an answer, but only the germ. The basic technique for converting a value into a string in the C pre-processor is indeed via the ‘#’ operator, but a simple transliteration of the proposed solution gets a compilation error: #define TEST_FUNC test_func #define TEST_FUNC_NAME #TEST_FUNC #include <stdio.h> … Read more
There are no macros called A or B, so on your #if line, A and B get replaced by 0, so you actually have: enum T { A = 1, B = 2 }; int main() { #if (0 == 0) std::cout << A << B; #endif } The preprocessor runs before the compiler knows … Read more
Go to https://godbolt.org/. Enter your code in the left pane and select compiler as gcc put the argument as -E in the right pane. Your pre-processed code will appear on the right.
gcc -E file.c or g++ -E file.cpp will do this for you. The -E switch forces the compiler to stop after the preprocessing phase, spitting all it’s got at the moment to standard output. Note: Surely you must have some #include directives. The included files get preprocessed, too, so you might get lots of output. … Read more
Consider this: std::string str = “Hello ” + “world”; // bad! Both the rhs and the lhs for operator + are char*s. There is no definition of operator + that takes two char*s (in fact, the language doesn’t permit you to write one). As a result, on my compiler this produces a “cannot add two … Read more
You use \ as a line continuation escape character. #define swap(a, b) { \ (a) ^= (b); \ (b) ^= (a); \ (a) ^= (b); \ } EDIT: As @abelenky pointed out in the comments, the \ character must be the last character on the line. If it is not (even if it is just … Read more
/#if works as usual if: #if __IPHONE_OS_VERSION_MAX_ALLOWED >= 30200 if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) { return YES; } #endif return NO; } /#ifdef means “if defined – some value or macros”: #ifdef RKL_APPEND_TO_ICU_FUNCTIONS #define RKL_ICU_FUNCTION_APPEND(x) _RKL_CONCAT(x, RKL_APPEND_TO_ICU_FUNCTIONS) #else // RKL_APPEND_TO_ICU_FUNCTIONS #define RKL_ICU_FUNCTION_APPEND(x) x #endif // RKL_APPEND_TO_ICU_FUNCTIONS or: #ifdef __OBJC__ #import <Foundation/Foundation.h> #endif Use this link for … Read more