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Fix undefined behavior in libdecnumber #81

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merged 1 commit into from
Feb 29, 2024
Merged

Fix undefined behavior in libdecnumber #81

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20 changes: 10 additions & 10 deletions decnumber-sys/decnumber/decBasic.c
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Original file line number Diff line number Diff line change
Expand Up @@ -331,7 +331,7 @@ static decFloat * decDivide(decFloat *result, const decFloat *dfl,
for (;;) { // inner loop -- calculate quotient unit
// strip leading zero units from acc (either there initially or
// from subtraction below); this may strip all if exactly 0
for (; *msua==0 && msua>=lsua;) msua--;
for (; msua>=lsua && *msua==0;) msua--;
accunits=(Int)(msua-lsua+1); // [maybe 0]
// subtraction is only necessary and possible if there are as
// least as many units remaining in acc for this iteration as
Expand Down Expand Up @@ -505,7 +505,7 @@ static decFloat * decDivide(decFloat *result, const decFloat *dfl,
// (must also continue to original lsu for correct quotient length)
if (lsua>acc+DIVACCLEN-DIVOPLEN) continue;
for (; msua>lsua && *msua==0;) msua--;
if (*msua==0 && msua==lsua) break;
if (msua==lsua && *msua==0) break;
} // outer loop

// all of the original operand in acc has been covered at this point
Expand Down Expand Up @@ -1533,8 +1533,8 @@ decFloat * decFloatAdd(decFloat *result,
umsd=acc+COFF+DECPMAX-1; // so far, so zero
if (ulsd>umsd) { // more to check
umsd++; // to align after checked area
for (; UBTOUI(umsd)==0 && umsd+3<ulsd;) umsd+=4;
for (; *umsd==0 && umsd<ulsd;) umsd++;
for (; umsd+3<ulsd && UBTOUI(umsd)==0;) umsd+=4;
for (; umsd<ulsd && *umsd==0;) umsd++;
}
if (*umsd==0) { // must be true zero (and diffsign)
num.sign=0; // assume +
Expand Down Expand Up @@ -2077,10 +2077,10 @@ decFloat * decFloatFMA(decFloat *result, const decFloat *dfl,
// remove leading zeros on both operands; this will save time later
// and make testing for zero trivial (tests are safe because acc
// and coe are rounded up to uInts)
for (; UBTOUI(hi->msd)==0 && hi->msd+3<hi->lsd;) hi->msd+=4;
for (; *hi->msd==0 && hi->msd<hi->lsd;) hi->msd++;
for (; UBTOUI(lo->msd)==0 && lo->msd+3<lo->lsd;) lo->msd+=4;
for (; *lo->msd==0 && lo->msd<lo->lsd;) lo->msd++;
for (; hi->msd+3<hi->lsd && UBTOUI(hi->msd)==0;) hi->msd+=4;
for (; hi->msd<hi->lsd && *hi->msd==0;) hi->msd++;
for (; lo->msd+3<lo->lsd && UBTOUI(lo->msd)==0;) lo->msd+=4;
for (; lo->msd<lo->lsd && *lo->msd==0;) lo->msd++;

// if hi is zero then result will be lo (which has the smaller
// exponent), which also may need to be tested for zero for the
Expand Down Expand Up @@ -2242,8 +2242,8 @@ decFloat * decFloatFMA(decFloat *result, const decFloat *dfl,
// all done except for the special IEEE 754 exact-zero-result
// rule (see above); while testing for zero, strip leading
// zeros (which will save decFinalize doing it)
for (; UBTOUI(lo->msd)==0 && lo->msd+3<lo->lsd;) lo->msd+=4;
for (; *lo->msd==0 && lo->msd<lo->lsd;) lo->msd++;
for (; lo->msd+3<lo->lsd && UBTOUI(lo->msd)==0;) lo->msd+=4;
for (; lo->msd<lo->lsd && *lo->msd==0;) lo->msd++;
if (*lo->msd==0) { // must be true zero (and diffsign)
lo->sign=0; // assume +
if (set->round==DEC_ROUND_FLOOR) lo->sign=DECFLOAT_Sign;
Expand Down
4 changes: 2 additions & 2 deletions decnumber-sys/decnumber/decCommon.c
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Expand Up @@ -264,7 +264,7 @@ static decFloat * decFinalize(decFloat *df, bcdnum *num,
// [this is quite expensive]
if (*umsd==0) {
for (; umsd+3<ulsd && UBTOUI(umsd)==0;) umsd+=4;
for (; *umsd==0 && umsd<ulsd;) umsd++;
for (; umsd<ulsd && *umsd==0;) umsd++;
length=ulsd-umsd+1; // recalculate
}
drop=MAXI(length-DECPMAX, DECQTINY-num->exponent);
Expand Down Expand Up @@ -416,7 +416,7 @@ static decFloat * decFinalize(decFloat *df, bcdnum *num,
// if exponent is >=emax may have to clamp, overflow, or fold-down
if (num->exponent>DECEMAX-(DECPMAX-1)) { // is edge case
// printf("overflow checks...\n");
if (*ulsd==0 && ulsd==umsd) { // have zero
if (ulsd==umsd && *ulsd==0) { // have zero
num->exponent=DECEMAX-(DECPMAX-1); // clamp to max
}
else if ((num->exponent+length-1)>DECEMAX) { // > Nmax
Expand Down
5 changes: 3 additions & 2 deletions decnumber-sys/decnumber/decNumber.c
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Expand Up @@ -3467,7 +3467,8 @@ uByte * decNumberGetBCD(const decNumber *dn, uByte *bcd) {
cut--;
if (cut>0) continue; // more in this unit
up++;
u=*up;
if (ub > bcd)
u=*up;
cut=DECDPUN;
}
#endif
Expand Down Expand Up @@ -4508,7 +4509,7 @@ static decNumber * decDivideOp(decNumber *res,
for (;;) { // inner forever loop
// strip leading zero units [from either pre-adjust or from
// subtract last time around]. Leave at least one unit.
for (; *msu1==0 && msu1>var1; msu1--) var1units--;
for (; msu1>var1 && *msu1==0; msu1--) var1units--;

if (var1units<var2ulen) break; // var1 too low for subtract
if (var1units==var2ulen) { // unit-by-unit compare needed
Expand Down