C++ #ifdef

#if, #elif, #else, and #endif directives (C/C++ …

docs.microsoft.comThe #if, #elif, #else, and #endif directives can nest in the text portions of other #if directives. Each nested #else, #elif, or #endif directive belongs to the closest preceding #if directive. All conditional-compilation directives, such as #if and #ifdef, must match a closing #endif directive before the end of file.

https://docs.microsoft.com/en-us/cpp/preprocessor/hash-if-hash-elif-hash-else-and-hash-endif-directives-c-cpp

#ifndef – C and C++ Syntax Reference – Cprogramming.com

cprogramming.com#ifndef checks whether the given token has been #defined earlier in the file or in an included file; if not, it includes the code between it and the closing #else or, if no #else is present, #endif statement. #ifndef is often used to make header files idempotent by defining a token once the file has been included and checking that the token was not set at the top of that file.

https://www.cprogramming.com/reference/preprocessor/ifndef.html

Ifdef (The C Preprocessor)

gcc.gnu.orgThe comment following the ‘#endif’ is not required, but it is a good practice if there is a lot of controlled text, because it helps people match the ‘#endif’ to the corresponding ‘#ifdef’. Older programs sometimes put MACRO directly after the ‘#endif’ without enclosing …

https://gcc.gnu.org/onlinedocs/cpp/Ifdef.html

C Language: #ifdef Directive – techonthenet.com

techonthenet.comIn the C Programming Language, the #ifdef directive allows for conditional compilation. The preprocessor determines if the provided macro exists before including the subsequent code in the compilation process.

https://www.techonthenet.com/c_language/directives/ifdef.php

c preprocessor – How to add a ‘or’ condition in #ifdef …

stackoverflow.comCombining C++ and C – how does #ifdef __cplusplus work? 2. Finding printf() calls outside #ifdef statements using Regex (POSIX) 3. Code complexity metrics and ifdefs. 8. Advantages of conditional-preprocessor over conditional statements. 1. How to count how many #ifdef clauses have at least an #elif but no #else in a set of C files? 8.

https://stackoverflow.com/questions/2998864/how-to-add-a-or-condition-in-ifdef

#pragma once versus #ifndef – C++ Forum

cplusplus.comFeb 19, 2009 · Borland’s Turbo Vision (a C++ Text GUI Framework) uses the double guarded style, and so does GNU’s autoconfig, although that style uses HAS_xxx, where HAS_xxx is externally defined. Grey Wolf. As I said, on small projects you will see not much of a difference. When the preprocessor is doing it’s business and finds an #include, it goes off loads …

http://www.cplusplus.com/forum/beginner/7877/

Conditional Compilation (#if, #ifdef, #ifndef, #else,…# …

cs.auckland.ac.nzThe end of the block or alternative block is marked by the #endif directive. If the condition checked by #if, #ifdef, or #ifndef is true (nonzero), then all lines between the matching #else (or #elif) and an #endif directive, if present, are ignored.

https://www.cs.auckland.ac.nz/references/unix/digital/AQTLTBTE/DOCU_078.HTM

Preprocessor – cppreference.com

en.cppreference.comNov 01, 2020 · conditionally compile of parts of source file (controlled by directive #if, #ifdef, #ifndef, #else, #elif and #endif). replace text macros while possibly concatenating or quoting identifiers (controlled by directives #define and #undef , and operators # and ## )

https://en.cppreference.com/w/cpp/preprocessor

#ifdef – #ifndef – #elseif – #elif – #else – #endif

people.vcu.eduThe #ifdef, #ifndef, #elseif, #elif, #else, and #endif are the logical directives of the preprocessor. These logical operations determine the fate of information processed the preprocessor.

http://www.people.vcu.edu/~jsiebers/mcnpinfo/dcomment/manual/node9.html

What is difference between #if and #ifdef

interviewsansar.comMar 06, 2017 · This Preprocessor Directives #ifdef only checks if the symbol is defined or not and doesn’t care for its value. For example, symbol LOG_ENABLED has been defined here and has a value 0 or 1. So, Below statement only checks if the symbol is defined and not it’s value, and all the code in this section will be enabled if it is defined.

https://www.interviewsansar.com/difference-between-preprocessor-if-and-ifdef/

C/C++ Preprocessor directives | Set 2 – GeeksforGeeks

geeksforgeeks.orgJul 08, 2017 · #ifdef: This directive is the simplest conditional directive. This block is called a conditional group. This block is called a conditional group. The controlled text will get included in the preprocessor output iff the macroname is defined.

https://www.geeksforgeeks.org/cpp-preprocessor-directives-set-2/

C++ Preprocessor – Tutorialspoint

tutorialspoint.com

https://www.tutorialspoint.com/cplusplus/cpp_preprocessor.htm

Simplifying templates and #ifdefs with if constexpr

blog.tartanllama.xyz

https://blog.tartanllama.xyz/if-constexpr/

c++ – unterminated #ifndef [SOLVED] | DaniWeb

daniweb.comHi,I spent all night trying to figure this out. Could someone take a look and show me what I’m missing? I getting this compiler error: unterminated #ifndef . But I have ifndef at the beginning and endif at the end of the class. //Header file. //Class definition for teh stack ADT #ifndef _mystack_H #

https://www.daniweb.com/programming/software-development/threads/389491/unterminated-ifndef

[Solved] What’s the theory behind this: #ifdef __cplusplus …

codeproject.comJan 10, 2010 · The C++ compiler, according with the extern "C" (__cplusplus is defined) directive: Produces a standard C DLL (i.e. the function use the C language mangling scheme) when building th DLL . consider the library as a C DLL when the header is included in a application (you know C++ compiler is able to link with C libraries).

https://www.codeproject.com/questions/51411/what-s-the-theory-behind-this-ifdef-cplusplus-ext

#ifdef vs #if vs #if defined – C / C++

bytes.comNov 14, 2005 · the "defined" pseudo-keyword (it is really just a magic identifier, rather than a keyword, since keywords do not exist in these phases. of translation): #ifdef …

https://bytes.com/topic/c/answers/220600-ifdef-vs-if-vs-if-defined

#ifdef – Can It Be Used With Logic Such as OR / AND?

cboard.cprogramming.comApr 21, 2006 · #ifdef – Can It Be Used With Logic Such as OR / AND? Hello, As is often the case when using #ifdef, I’m using #ifdef to distiguish compiler directives for the various platforms that I’m using or the various compilers of which I’m using to compile.

https://cboard.cprogramming.com/c-programming/78316-sharpifdef-can-used-logic-such.html

The code under #ifdef _WIN64 checking is not working in …

social.msdn.microsoft.comSep 27, 2012 · R-VR wrote: I’m developing an application that runs both 32bit and 64bit machines using VC++ code. And, I’m writing some functions like the following format: #ifdef _WIN64 Calling "Wow64DisableWow64FsRedirection()" and do some code here and then calling "Wow64RevertWow64FsRedirection()" API’s. #else Do some 32bit code #endif. You seem to be under impression that "#ifdef

https://social.msdn.microsoft.com/Forums/en-US/bc30931e-57a9-48eb-b90e-52cc426b1b51/the-code-under-ifdef-win64-checking-is-not-working-in-64bit-machines-why

183444 – #ifdef __cplusplus ignored in C++ project type

bz.apache.orgCreated attachment 96644 Sample Screenshot of .h file of a C++ project. When in a C++ project, and viewing code wrapped by: #ifdef __cplusplus /* this is ignored */ #else /* this is not ignored, and should be */ #endif The __cplusplus #define should be recognized when in a C++ project.

https://bz.apache.org/netbeans/show_bug.cgi?id=183444

C++ preprocessor #if #else #endif #include macro vs function

tutorialdost.comC++ provides the following preprocessor directives: … The #ifdef preprocessor directive is used to check whether the macro-name is previously defined or not, if defined then the statements given between #ifdef and #else will get execute. Syntax of #ifdef preprocessor directive …

http://www.tutorialdost.com/Cpp-Programming-Tutorial/32-Cpp-Perprocessors.aspx

C preprocessor – Wikipedia

en.wikipedia.orgThe C preprocessor or cpp is the macro preprocessor for the C, Objective-C and C++ computer programming languages.The preprocessor provides the ability for the inclusion of header files, macro expansions, conditional compilation, and line control.. In many C implementations, it is a separate program invoked by the compiler as the first part of translation. …

https://en.wikipedia.org/wiki/C_preprocessor

Arduino Preprocessor Directives Tutorial – ifdef & endif

deviceplus.comJun 06, 2017 · #ifdef macro_name //compile this code if macro_name exists #endif The above is a just shorthand for #if defined , which can be used to test multiple macros in a single condition. Note that every condition has to end with #endif directive, to specify which parts of the code are affected by the condition, and which ones are not.

https://www.deviceplus.com/arduino/arduino-preprocessor-directives-tutorial/

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