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Is there some "nice" way to check if a variable passed to a macro is a pointer? e.g.
#define IS_PTR(x) something
int a;
#if IS_PTR(a)
printf("a pointer we have\n");
#else
printf("not a pointer we have\n");
#endif
The idea is that this is not done run-time but compile-time, as in: we get different code depending on if the variable is a pointer or not. So I would like IS_PTR() to evaluate to some kind of constant expression in some way. Am I going about this idea all the wrong way?
372
In macros, no type checking(incompatible operand, etc.) is done and thus use of macros can lead to errors/side-effects in some cases. However, this is not the case with functions. Also, macros do not check for compilation error (if any).
To define a macro that uses arguments, you insert parameters between the pair of parentheses in the macro definition that make the macro function-like. The parameters must be valid C identifiers, separated by commas and optionally whitespace.
A macro is a piece of code in a program that is replaced by the value of the macro. Macro is defined by #define directive. Whenever a macro name is encountered by the compiler, it replaces the name with the definition of the macro. Macro definitions need not be terminated by a semi-colon(;).
Predefined Macros in C99 standard: __cplusplus: __cplusplus Macro is defined when the C++ compiler is used. It is used to test whether a header is compiled by a C compiler or a C++ compiler. This macro gives value similar to __STDC_VERSION__, in that it expands to a version number.
On Clang and GCC, __builtin_classify_type(P) evaluates to 5 if P is an object with a pointer type.
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