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Make APFloat's string-parsing routines a bit safer against very large exponents.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97278 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
John McCall 2010-02-26 22:20:41 +00:00
parent 1869ac8b71
commit 8b3f3307a2
2 changed files with 23 additions and 2 deletions
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18
lib/Support/APFloat.cpp
View File

@ -17,6 +17,7 @@
#include "llvm/ADT/FoldingSet.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MathExtras.h"
#include <limits.h>
#include <cstring>
using namespace llvm;
@ -2345,11 +2346,24 @@ APFloat::convertFromDecimalString(const StringRef &str, roundingMode rounding_mo
if (decDigitValue(*D.firstSigDigit) >= 10U) {
category = fcZero;
fs = opOK;
} else if ((D.normalizedExponent + 1) * 28738
<= 8651 * (semantics->minExponent - (int) semantics->precision)) {
/* Check whether the normalized exponent is high enough to overflow
max during the log-rebasing in the max-exponent check below. */
} else if (D.normalizedExponent - 1 > INT_MAX / 42039) {
fs = handleOverflow(rounding_mode);
/* If it wasn't, then it also wasn't high enough to overflow max
during the log-rebasing in the min-exponent check. Check that it
won't overflow min in either check, then perform the min-exponent
check. */
} else if (D.normalizedExponent - 1 < INT_MIN / 42039 ||
(D.normalizedExponent + 1) * 28738 <=
8651 * (semantics->minExponent - (int) semantics->precision)) {
/* Underflow to zero and round. */
zeroSignificand();
fs = normalize(rounding_mode, lfLessThanHalf);
/* We can finally safely perform the max-exponent check. */
} else if ((D.normalizedExponent - 1) * 42039
>= 12655 * semantics->maxExponent) {
/* Overflow and round. */

7
unittests/ADT/APFloatTest.cpp
View File

@ -236,6 +236,13 @@ TEST(APFloatTest, fromDecimalString) {
EXPECT_EQ(2.05e12, APFloat(APFloat::IEEEdouble, "002.05000e12").convertToDouble());
EXPECT_EQ(2.05e+12, APFloat(APFloat::IEEEdouble, "002.05000e+12").convertToDouble());
EXPECT_EQ(2.05e-12, APFloat(APFloat::IEEEdouble, "002.05000e-12").convertToDouble());
// These are "carefully selected" to overflow the fast log-base
// calculations in APFloat.cpp
EXPECT_TRUE(APFloat(APFloat::IEEEdouble, "99e99999").isInfinity());
EXPECT_TRUE(APFloat(APFloat::IEEEdouble, "-99e99999").isInfinity());
EXPECT_TRUE(APFloat(APFloat::IEEEdouble, "1e-99999").isPosZero());
EXPECT_TRUE(APFloat(APFloat::IEEEdouble, "-1e-99999").isNegZero());
}
TEST(APFloatTest, fromHexadecimalString) {