https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114746
--- Comment #7 from Vincent Lefèvre <vincent-gcc at vinc17 dot net> --- BTW, in /usr/include/math.h from the GNU libc 2.37: # define M_PI 3.14159265358979323846 /* pi */ i.e. M_PI is defined with 21 digits in base 10, which corresponds to about 70 digits in base 2, thus with the apparent intent to be accurate in extended precision (64 digits).