MPFR_PREC_MAX redefined.

MPFR_INTPREC_MAX defined (internal maximum precision).
Some integer overflow detection.


git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@1666 280ebfd0-de03-0410-8827-d642c229c3f4

4 files changed, 40 insertions, 25 deletions

diff --git a/mpfr-impl.h b/mpfr-impl.h
index bc917d5ca..8300e9e3b 100644
--- a/mpfr-impl.h
+++ b/mpfr-impl.h
@@ -30,6 +30,12 @@ typedef unsigned long int       mp_size_unsigned_t;
 
 #define MP_LIMB_T_ONE ((mp_limb_t) 1)
 
+#if (BITS_PER_MP_LIMB & (BITS_PER_MP_LIMB - 1))
+#error "BITS_PER_MP_LIMB must be a power of 2"
+#endif
+
+#define MPFR_INTPREC_MAX (ULONG_MAX & ~(unsigned long) (BITS_PER_MP_LIMB - 1))
+
 /* Assertions */
 
 /* Compile with -DWANT_ASSERT to check all assert statements */
diff --git a/mpfr.h b/mpfr.h
index 52ac36a88..d64d7c072 100644
--- a/mpfr.h
+++ b/mpfr.h
@@ -58,8 +58,10 @@ MA 02111-1307, USA. */
 
 typedef unsigned long int mp_prec_t; /* easy to change if necessary */
 #define MPFR_PREC_MIN 2
-#define MPFR_PREC_MAX ULONG_MAX
-typedef int mp_rnd_t;                /* preferred to char */
+#define MPFR_PREC_MAX (ULONG_MAX >> 1)
+/* Limit mainly due to the multiplication code. */
+
+typedef int mp_rnd_t;
 
 typedef struct {  
   mp_prec_t _mpfr_prec; /* WARNING : for the mpfr type, the precision */
diff --git a/mul.c b/mul.c
index 232efb95a..343eebc90 100644
--- a/mul.c
+++ b/mul.c
@@ -136,12 +136,13 @@ mpfr_mul (mpfr_ptr a, mpfr_srcptr b, mpfr_srcptr c, mp_rnd_t rnd_mode)
   bn = (bq-1)/BITS_PER_MP_LIMB + 1; /* number of significant limbs of b */
   cn = (cq-1)/BITS_PER_MP_LIMB + 1; /* number of significant limbs of c */
 
-  MPFR_ASSERTN(bq + cq >= bq); /* no integer overflow */
-  tn = (bq + cq - 1) / BITS_PER_MP_LIMB + 1;
-
   MPFR_ASSERTN((mp_size_unsigned_t) bn + cn <= MP_SIZE_T_MAX);
-  k = bn + cn; /* effective nb of limbs used by b*c (=tn or tn+1) */
+  k = bn + cn; /* effective nb of limbs used by b*c (= tn or tn+1) below */
+
+  MPFR_ASSERTN(bq + cq >= bq); /* no integer overflow */
+  tn = (bq + cq - 1) / BITS_PER_MP_LIMB + 1; /* <= k, thus no int overflow */
 
+  MPFR_ASSERTN(k <= ((size_t) -1) / BYTES_PER_MP_LIMB);
   TMP_MARK(marker); 
   tmp = (mp_limb_t *) TMP_ALLOC((size_t) k * BYTES_PER_MP_LIMB);
 
diff --git a/sqrt.c b/sqrt.c
index c673642ac..3da68d280 100644
--- a/sqrt.c
+++ b/sqrt.c
@@ -34,6 +34,7 @@ mpfr_sqrt (mpfr_ptr r, mpfr_srcptr u, mp_rnd_t rnd_mode)
   mp_size_t rsize;
   mp_size_t err;
   mp_limb_t q_limb;
+  int odd_exp_u;
   long rw, nw, k; 
   int inexact = 0, t;
   unsigned long cc = 0; 
@@ -81,29 +82,32 @@ mpfr_sqrt (mpfr_ptr r, mpfr_srcptr u, mp_rnd_t rnd_mode)
         MPFR_RET(0); /* zero is exact */
       }
 
-  up = MPFR_MANT(u);
-  usize = (MPFR_PREC(u) - 1)/BITS_PER_MP_LIMB + 1; 
+    up = MPFR_MANT(u);
+    usize = (MPFR_PREC(u) - 1)/BITS_PER_MP_LIMB + 1;
 
 #ifdef DEBUG
-      printf("Entering square root : "); 
-      for(k = usize - 1; k >= 0; k--) { printf("%lu ", up[k]); }
-      printf(".\n"); 
+    printf("Entering square root : ");
+    for(k = usize - 1; k >= 0; k--) { printf("%lu ", up[k]); }
+    printf(".\n");
 #endif
 
-  /* Compare the mantissas */
-  
-  rsize = ((MPFR_PREC(r) + 2 + (MPFR_EXP(u) & 1))/BITS_PER_MP_LIMB + 1) << 1; 
-  rrsize = (MPFR_PREC(r) + 2 + (MPFR_EXP(u) & 1))/BITS_PER_MP_LIMB + 1;
-  /* One extra bit is needed in order to get the square root with enough
-     precision ; take one extra bit for rrsize in order to solve more 
-     easily the problem of rounding to nearest.
-     Need to have 2*rrsize = rsize...
-     Take one extra bit if the exponent of u is odd since we shall have
-     to shift then.
-  */
+    /* Compare the mantissas */
+
+    odd_exp_u = (unsigned int) MPFR_EXP(u) & 1;
+    MPFR_ASSERTN(MPFR_PREC(r) <= MPFR_INTPREC_MAX - 3);
+    rrsize = (MPFR_PREC(r) + 2 + odd_exp_u) / BITS_PER_MP_LIMB + 1;
+    MPFR_ASSERTN(rrsize <= MP_SIZE_T_MAX/2);
+    rsize = rrsize << 1;
+    /* One extra bit is needed in order to get the square root with enough
+       precision ; take one extra bit for rrsize in order to solve more
+       easily the problem of rounding to nearest.
+       Need to have 2*rrsize = rsize...
+       Take one extra bit if the exponent of u is odd since we shall have
+       to shift then.
+    */
 
   TMP_MARK(marker0); 
-  if (MPFR_EXP(u) & 1) /* Shift u one bit to the right */
+  if (odd_exp_u) /* Shift u one bit to the right */
     {
       if (MPFR_PREC(u) & (BITS_PER_MP_LIMB - 1))
 	{
@@ -120,8 +124,10 @@ mpfr_sqrt (mpfr_ptr r, mpfr_srcptr u, mp_rnd_t rnd_mode)
 	}
     }
 
-  MPFR_EXP(r) = ((MPFR_EXP(u) + (MPFR_EXP(u) & 1)) / 2) ;  
-  
+  MPFR_EXP(r) = MPFR_EXP(u) != MPFR_EMAX_MAX
+    ? (MPFR_EXP(u) + odd_exp_u) / 2
+    : (MPFR_EMAX_MAX - 1) / 2 + 1;
+
   do
     {
       TMP_MARK (marker);