Menu
In my /usr/include directory, there are at least two variants of #define NULL 0 tailored for C++ code1:
#define NULL 0 // from rpc/types.h #define NULL (0) // from libio.h I feel like there must be a counter-example where the first one would not be safe, but I was not able to produce it.
Otherwise, is there some compelling argument about why it would be safe to not include the parentheses in this case (e.g., an informal "proof of correctness")?
1 That is, without including the variant #define NULL ((void*)0), which is useful for C but invalid in C++.
557
Working of C Preprocessor. The C preprocessor is a macro preprocessor (allows you to define macros) that transforms your program before it is compiled. These transformations can be the inclusion of header files, macro expansions, etc. All preprocessing directives begin with a # symbol.
The macro and its parameters should be enclosed in parentheses. When macro parameters or expression are not parenthesized, the intended logic may get disrupted after expanding the macro.
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.
There is no difference. The only operators with higher priority are ::, ++ and -- and they are not applicable on 0 nor (0).
The only funny difference I see is obfuscation :
#define NULL (0) void f(int x) { // Do something with x } int main() { f NULL; // This code compiles return 0; } If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
