Macros are simply textual substitution, so in your example writing TIMER_100_MS in a program is a fancy way of writing 32768 / 10. Therefore, the question is when the compiler would evaluate 32768 / 10, which is a constant integral expression. I don’t think the standard requires any particular behavior here (since run-time and compile-time … Read more
You’re assuming __func__ is a macro, but it’s not. It’s a conditionally-supported predefined identifier, so you can’t check it with #if defined or #ifdef. If the compilers have no way of telling you whether this is supported (they could via a _FUNC_SUPPORTED or something, I’m not saying they actually are doing this), you’ll have to … Read more
No, you can’t. Comments are removed from the code before any processing of preprocessing directives begin. For this reason you can’t include comment into a macro. Also, any attempts to “form” a comment later by using any macro trickery are not guaranteed to work. The compiler is not required to recognize “late” comments as comments. … Read more
Replacement only occurrs for a function-like macro if the macro name is followed by a left parenthesis. So, the following all invoke the function-like macro MY_MACRO(): MY_MACRO() MY_MACRO ( ) MY_MACRO ( ) But this would not: MY_MACRO SomethingElse It depends on how you are using the macro and what it is used for as … Read more
Got it! #define anlb /* */ A /* */ B anlb anlb gcc -E -CC nl.c /* */ A /* */ B /* */ A /* */ B
This may not work for the general case (I don’t think there’s a general solution to what you’re asking for), but for your specific example you might consider changing this sequence of code: #if(DEBUG_PRINT == 1) printf(“%s”, “Testing”); #endif to: if (DEBUG_PRINT == 1) { printf(“%s”, “Testing”); } It’s no more verbose and will fail … Read more
Try using #undef: #define FOO “” #if …. #undef FOO #define FOO “Foo, good sir” #endif
It doesn’t use the preprocessor, but sizeof is resolved at compile time. If your string is in an array, you can use that to determine its length at compile time: static const char string[] = “bob”; #define STRLEN(s) (sizeof(s)/sizeof(s[0])) Keep in mind the fact that STRLEN above will include the null terminator, unlike strlen().
What you are asking for is possible but needs a bit of work. Define a preprocessor variable in your csproj <PropertyGroup Condition=” ‘$(OS)’ == ‘Windows_NT’ “> <DefineConstants>_WINDOWS</DefineConstants> </PropertyGroup> Use that in your code #if _WINDOWS // your windows stuff #else // your *nix stuff #endif I find this technique useful when you have constants that … Read more
You can simply write: #elif defined X Which should be compatible with all ANSI-C compatible compilers.