Rationale (February, 2014):

EWG determined that no action should be taken on this issue.

Rationale (October, 2012):

CWG felt that whether this form of these macros needed to be supported in C++ should be examined by EWG.

The format macros that are part of <inttypes.h> (incorporated into C++11 as <cinttypes>) are conventionally written with no whitespace separating them from the rest of the format string, e.g.,

  printf("foo = "PRIu32", bar = "PRIi8"\n", foo, bar);
  printf("baz = "PRIu32"\n", baz);

This usage conflicts with user-defined literals.