Why was it is not an easy question. Maybe it’s time to ask the standard committee why were they as crazy as to standardize (the now removed) gets() function as well? Sometimes, the standard is simply brain-dead, whether we want it or not. The first C was not today’s C. It was not “designed” to … Read more
In C, it’s common to define macros that do some stuff getting the verbatim argument, and at the same time define functions to be able to get the address of it transparently. // could evaluate at compile time if __builtin_sin gets // special treatment by the compiler #define sin(x) __builtin_sin(x) // parentheses avoid substitution by … Read more
If you’re using the gcc preprocessor: -P Inhibit generation of linemarkers in the output from the preprocessor. This might be useful when running the preprocessor on something that is not C code, and will be sent to a program which might be confused by the linemarkers. from gcc cpp man page
C Preprocessor works top to bottom irrespective of function calls. It is effective from that point (line) in whatever the file that macro is defined, until corresponding undef or till end of the translation unit. So, your code would become, # define i 20 // from now on, all token i should become 20 void … Read more
Expanding __func__ at preprocessing time requires the preprocessor to know which function it’s processing. The preprocessor generally doesn’t know that, because parsing happens after the preprocessor is already done. Some implementations combine the preprocessing and the parsing, and in those implementations, it would have been possible for __func__ to work the way you’d like it … Read more
For a long time, CMake had the add_definitions command for this purpose. However, recently the command has been superseded by a more fine grained approach (separate commands for compile definitions, include directories, and compiler options). An example using the new add_compile_definitions: add_compile_definitions(OPENCV_VERSION=${OpenCV_VERSION}) add_compile_definitions(WITH_OPENCV2) Or: add_compile_definitions(OPENCV_VERSION=${OpenCV_VERSION} WITH_OPENCV2) The good part about this is that it circumvents … Read more
The numbers following the filename are flags: 1: This indicates the start of a new file. 2: This indicates returning to a file (after having included another file). 3: This indicates that the following text comes from a system header file, so certain warnings should be suppressed. 4: This indicates that the following text should … Read more
How much effort are you willing to go to? There’s an obnoxiously obscure way to do it but it requires you to set up a dummy directory to hold surrogates for the system headers. OTOH, it doesn’t require any changes in any of your source code. The same technique works equally well for C code. … Read more
First of all, we know we can count on Boost.Preprocessor for our looping needs. However, the generated code must work on its own. Unfortunately, #ifdef cannot work as a result of macro expansion, so there’s no way to generate the code in your question. Are we toasted? Not yet! We can take advantage of the … Read more
As stated earlier, the only “real” way to detect Big Endian is to use runtime tests. However, sometimes, a macro might be preferred. Unfortunately, I’ve not found a single “test” to detect this situation, rather a collection of them. For example, GCC recommends : __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ . However, this only works with latest versions, … Read more