Catch division edge case of (/ fx-least -1).

Thanks for Jim Rees for reporting.
ashinn · Feb 22, 2024 · 56ef426 · 56ef426
1 parent 29dd1a3
commit 56ef426
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diff --git a/bignum.c b/bignum.c
@@ -1762,6 +1762,9 @@ sexp sexp_quotient (sexp ctx, sexp a, sexp b) {
     break;
   case SEXP_NUM_FIX_FIX:
     r = sexp_fx_div(a, b);
+    if ((sexp_sint_t)a < 0 && (sexp_sint_t)b < 0 && (sexp_sint_t)r < 0) {
+      r = sexp_quotient(ctx, tmp=sexp_fixnum_to_bignum(ctx, a), b);
+    }
     break;
   case SEXP_NUM_FIX_BIG:
     r = SEXP_ZERO;

diff --git a/tests/r7rs-tests.scm b/tests/r7rs-tests.scm
@@ -904,6 +904,13 @@
 (test 3/20 (/ 3 4 5))
 (test 1/3 (/ 3))
 
+(test 1073741824 (/ -1073741824 -1))
+(test 1073741824 (quotient -1073741824 -1))
+(test 0 (remainder -1073741824 -1))
+(test 4611686018427387904 (/ -4611686018427387904 -1))
+(test 4611686018427387904 (quotient -4611686018427387904 -1))
+(test 0 (remainder -4611686018427387904 -1))
+
 (test 7 (abs -7))
 (test 7 (abs 7))
 

diff --git a/vm.c b/vm.c
@@ -1891,6 +1891,9 @@ sexp sexp_apply (sexp ctx, sexp proc, sexp args) {
       if (tmp2 == SEXP_ZERO)
         sexp_raise("divide by zero", SEXP_NULL);
       _ARG1 = sexp_fx_div(tmp1, tmp2);
+      if ((sexp_sint_t)tmp1 < 0 && (sexp_sint_t)tmp2 < 0 && (sexp_sint_t)_ARG1 < 0) {
+        _ARG1 = sexp_quotient(ctx, tmp1=sexp_fixnum_to_bignum(ctx, tmp1), tmp2);
+      }
     }
 #if SEXP_USE_BIGNUMS
     else {