What is the UINT64_C macro in C?
I saw this code:
bool contains_zero_byte(uint64 v) {
return (((v)-UINT64_C(0x0101010101010101))
& ~(v)&UINT64_C(0x8080808080808080));
}What is UINT64_C(0x0101010101010101) doing? UINT64_C is a macro defined as:
// Appends the correct suffix to a 64-bit unsigned integer literal.
#define UINT64_C(c) c ## ULLThe ## token instructs the preprocessor to “paste together” the tokens on either side of it. So UINT64_C(0x0101010101010101) results in the output 0x0101010101010101ULL.
But what is ULL in 0x0101010101010101ULL? I’ll write more about these suffixes in the next post.
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