I believe that author's point was the size of the resulting generated code, which is fair. The original intent of making it a macro was to get a faster version

I believe that author's point was the size of the resulting generated code, which is fair. The original intent of making it a macro was to get a faster version of printf. However, as it turns out the major time sink in printf is not the formatting, but converting binary into decimal, so specializing on the format string doesn't actually help.