Vincent Lefevre <vinc...@vinc17.net> writes: > ./configure --with-mini-gmp=/home/vlefevre/software/gmp/mini-gmp CC=gcc-13 > CFLAGS="-O2 -fsanitize=undefined -fno-sanitize-recover > -DMINI_GMP_LIMB_TYPE=short" > > I get lots of failures in mini-gmp.c (I suspect that the errors were > hidden by some optimization in GCC 12 and before).
Interesting. It seems rather undocumented what settings of MINI_GMP_LIMB_TYPE are supported/tested. I can try to guess your motivation for using such a small size, but can you give a bit more context? > For instance: > > cventin:...ftware/mpfr/tests> ./texceptions > mini-gmp.c:993:7: runtime error: signed integer overflow: 46604 * 61440 > cannot be represented in type 'int' That looks like a problem, since we aim to stick to standard C. > I suppose that the simplest solution would be to add a cast to > unsigned long, so that the multiplication is done in this type (and > the subtraction too as a consequence), as this should be the largest > MINI_GMP_LIMB_TYPE size... hoping that the compiler will optimize. I think it's desirable to support setting MINI_GMP_LIMB_TYPE to long long (which would make sense, e.g., on 64-bit windows, where for some historical reasons long is still only 32 bits). Unconditionally casting to unsigned long would break that. > Otherwise the sizes of the types could be checked like in > gmp_umul_ppmm. I think that's needed, to be able to support any size of MINI_GMP_LIMB_TYPE. Something like #define umullo_limb(u, v) \ (sizeof(mp_limb_t) >= sizeof(int)) ? (u)*(v) : (unsigned int)(u) * (v)) If I understand you correctly, the two multiplies in gmp_udiv_qrnnd_preinv and gmp_udiv_qr_3by2 are the only places where we need a mullo operation, i.e., producing the low limb of a limb product? Regards, /Niels -- Niels Möller. PGP key CB4962D070D77D7FCB8BA36271D8F1FF368C6677. Internet email is subject to wholesale government surveillance. _______________________________________________ gmp-bugs mailing list gmp-bugs@gmplib.org https://gmplib.org/mailman/listinfo/gmp-bugs
