8.1.2 ‘PRId64 is not a valid printf conversion specifier’

The following configuration warning was encountered on various BSD Unix systems (OpenBSD 3.4 and FreeBSD 4.10-BETA , both IA-32) and inhibited the building of the coNCePTuaL run-time library:

PRId64 is not a valid printf conversion specifier for values of type int64_t

The config.log file indicated the source of the problem was a ‘syntax error before `PRId64'’ that was reported when compiling a sample program. A brief search revealed that the PRId64 macro is not defined in any of the standard C header files on the systems in question. The solution turned out to be to configure with ./configure --with-printf-format='"lld"' to instruct the C compiler to use printf() format strings such as ‘%lld’ when outputting 64-bit signed integers. The extra pair of double quotes is required because the conversion specifier is used in constructs like the following:

printf ("The number is %10" conversion-specifier "!\n", num);

Most—but apparently not all—C compilers define the PRId64 macro (“PRInt signed decimal number of length 64 bits”) in one the standard header files. Typical values of PRId64 include the strings "lld" and "ld".