With: #define __STDC_WANT_DEC_FP__ #include <stdio.h>
int main (void) { double d = 0.1; _Decimal64 e = 0.1dd; printf ("%.20f\n", d); printf ("%Da\n", e); printf ("%De\n", e); printf ("%Df\n", e); printf ("%Dg\n", e); return 0; } $ gcc-snapshot -Wall tst.c tst.c: In function 'main': tst.c:9:3: warning: use of 'D' length modifier with 'a' type character while WG14/N1312 says: D Specifies that a following a, A, e, E, f, F, g, or G conversion specifier applies to a _Decimal64 argument. -- Summary: Incorrect warning: use of 'D' length modifier with 'a' type character Product: gcc Version: unknown Status: UNCONFIRMED Severity: minor Priority: P3 Component: c AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: vincent at vinc17 dot org http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43673