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Rework XPath rounding functions

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Use the C library's floor and ceil functions. The old code was overly
complicated for no apparent reason and could result in undefined
behavior when handling NaNs (found with afl-fuzz and UBSan).

Fix wrong comment in xmlXPathRoundFunction. The implementation was
already following the spec and rounding half up.
This commit is contained in:
Nick Wellnhofer
2016-04-21 13:41:09 +02:00
parent 43f50f4dfc
commit 4bebb030db
3 changed files with 100 additions and 56 deletions
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71
xpath.c
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@@ -9675,18 +9675,6 @@ xmlXPathSumFunction(xmlXPathParserContextPtr ctxt, int nargs) {
xmlXPathReleaseObject(ctxt->context, cur);
}
/*
* To assure working code on multiple platforms, we want to only depend
* upon the characteristic truncation of converting a floating point value
* to an integer. Unfortunately, because of the different storage sizes
* of our internal floating point value (double) and integer (int), we
* can't directly convert (see bug 301162). This macro is a messy
* 'workaround'
*/
#define XTRUNC(f, v) \
f = fmod((v), INT_MAX); \
f = (v) - (f) + (double)((int)(f));
/**
* xmlXPathFloorFunction:
* @ctxt: the XPath Parser context
@@ -9699,19 +9687,11 @@ xmlXPathSumFunction(xmlXPathParserContextPtr ctxt, int nargs) {
*/
void
xmlXPathFloorFunction(xmlXPathParserContextPtr ctxt, int nargs) {
double f;
CHECK_ARITY(1);
CAST_TO_NUMBER;
CHECK_TYPE(XPATH_NUMBER);
XTRUNC(f, ctxt->value->floatval);
if (f != ctxt->value->floatval) {
if (ctxt->value->floatval > 0)
ctxt->value->floatval = f;
else
ctxt->value->floatval = f - 1;
}
ctxt->value->floatval = floor(ctxt->value->floatval);
}
/**
@@ -9726,28 +9706,11 @@ xmlXPathFloorFunction(xmlXPathParserContextPtr ctxt, int nargs) {
*/
void
xmlXPathCeilingFunction(xmlXPathParserContextPtr ctxt, int nargs) {
double f;
CHECK_ARITY(1);
CAST_TO_NUMBER;
CHECK_TYPE(XPATH_NUMBER);
#if 0
ctxt->value->floatval = ceil(ctxt->value->floatval);
#else
XTRUNC(f, ctxt->value->floatval);
if (f != ctxt->value->floatval) {
if (ctxt->value->floatval > 0)
ctxt->value->floatval = f + 1;
else {
if (ctxt->value->floatval < 0 && f == 0)
ctxt->value->floatval = xmlXPathNZERO;
else
ctxt->value->floatval = f;
}
}
#endif
}
/**
@@ -9759,7 +9722,7 @@ xmlXPathCeilingFunction(xmlXPathParserContextPtr ctxt, int nargs) {
* number round(number)
* The round function returns the number that is closest to the
* argument and that is an integer. If there are two such numbers,
* then the one that is even is returned.
* then the one that is closest to positive infinity is returned.
*/
void
xmlXPathRoundFunction(xmlXPathParserContextPtr ctxt, int nargs) {
@@ -9769,25 +9732,21 @@ xmlXPathRoundFunction(xmlXPathParserContextPtr ctxt, int nargs) {
CAST_TO_NUMBER;
CHECK_TYPE(XPATH_NUMBER);
if ((xmlXPathIsNaN(ctxt->value->floatval)) ||
(xmlXPathIsInf(ctxt->value->floatval) == 1) ||
(xmlXPathIsInf(ctxt->value->floatval) == -1) ||
(ctxt->value->floatval == 0.0))
f = ctxt->value->floatval;
/* Test for zero to keep negative zero unchanged. */
if ((xmlXPathIsNaN(f)) || (f == 0.0))
return;
XTRUNC(f, ctxt->value->floatval);
if (ctxt->value->floatval < 0) {
if (ctxt->value->floatval < f - 0.5)
ctxt->value->floatval = f - 1;
else
ctxt->value->floatval = f;
if (ctxt->value->floatval == 0)
ctxt->value->floatval = xmlXPathNZERO;
} else {
if (ctxt->value->floatval < f + 0.5)
ctxt->value->floatval = f;
else
ctxt->value->floatval = f + 1;
if ((f >= -0.5) && (f < 0.0)) {
/* Negative zero. */
ctxt->value->floatval = xmlXPathNZERO;
}
else {
double rounded = floor(f);
if (f - rounded >= 0.5)
rounded += 1.0;
ctxt->value->floatval = rounded;
}
}