How do I concatenate wide string literals with PRId32, PRIu64, etc.?

Question

Suppose I need to print a formatted string with an int32_t using the printf format specifier from .

int32_t i = 0;
pr         


        

Answer 1

The problem is twofold. First, as noted in rici's answer, C99 and C++11 both added support for concatenating narrow string literals and wide string literals together, so you should not need to widen the narrow literal by prepending the L. Visual C++ does not yet support this feature for either C or C++.

Because the compiler does not yet support this feature, we should in the libraries make it possible for you to explicitly widen these string literals using a technique like the one in your answer. Unfortunately, we've defined these macros in a way such that they may expand to multiple string literals. E.g., PRId32 expands to "l" "d".

This is valid, but it does prevent you from widening, because there is no way to prepend an L to the second string literal (to make "d" into L"d"). I'm afraid I don't see a way to make this work without (re)defining the macros yourself.

I've opened a bug internally so that if the compiler does not add support for concatenation of mixed-width literals during preprocessing in the next release, we can revisit these definitions to possibly make it possible to widen them explicitly.