gcc/testsuite/gcc.dg/fltconst-pedantic-dfp.c

/* { dg-do compile } */
/* { dg-options "-pedantic" } */

double a = 1.dl;	/* { dg-warning "decimal float" } */
double b = 1.df;	/* { dg-warning "decimal float" } */
double c = 1.dd;	/* { dg-warning "decimal float" } */