AuroraMiddleware/qt5base-lts
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Remove type punning from ucstrncmp

Browse Source 
Type punning is UB.

Change-Id: I0022d2a38136d80f5ddda21cea7dc0968c736242
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
This commit is contained in:
Erik Verbruggen 2016-10-06 16:32:49 +02:00
parent e70e168abb
commit 30b7278c5c
1 changed files with 23 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

48
src/corelib/tools/qstring.cpp
View File

@ -480,48 +480,46 @@ static int ucstrncmp(const QChar *a, const QChar *b, int l)
if (!l)
return 0;
union {
const QChar *w;
const quint32 *d;
quintptr value;
} sa, sb;
sa.w = a;
sb.w = b;
// check alignment
if ((sa.value & 2) == (sb.value & 2)) {
if ((reinterpret_cast<quintptr>(a) & 2) == (reinterpret_cast<quintptr>(b) & 2)) {
// both addresses have the same alignment
if (sa.value & 2) {
if (reinterpret_cast<quintptr>(a) & 2) {
// both addresses are not aligned to 4-bytes boundaries
// compare the first character
if (*sa.w != *sb.w)
return sa.w->unicode() - sb.w->unicode();
if (*a != *b)
return a->unicode() - b->unicode();
--l;
++sa.w;
++sb.w;
++a;
++b;
// now both addresses are 4-bytes aligned
}
// both addresses are 4-bytes aligned
// do a fast 32-bit comparison
const quint32 *e = sa.d + (l >> 1);
for ( ; sa.d != e; ++sa.d, ++sb.d) {
if (*sa.d != *sb.d) {
if (*sa.w != *sb.w)
return sa.w->unicode() - sb.w->unicode();
return sa.w[1].unicode() - sb.w[1].unicode();
const quint32 *da = reinterpret_cast<const quint32 *>(a);
const quint32 *db = reinterpret_cast<const quint32 *>(b);
const quint32 *e = da + (l >> 1);
for ( ; da != e; ++da, ++db) {
if (*da != *db) {
a = reinterpret_cast<const QChar *>(da);
b = reinterpret_cast<const QChar *>(db);
if (*a != *b)
return a->unicode() - b->unicode();
return a[1].unicode() - b[1].unicode();
}
}
// do we have a tail?
return (l & 1) ? sa.w->unicode() - sb.w->unicode() : 0;
a = reinterpret_cast<const QChar *>(da);
b = reinterpret_cast<const QChar *>(db);
return (l & 1) ? a->unicode() - b->unicode() : 0;
} else {
// one of the addresses isn't 4-byte aligned but the other is
const QChar *e = sa.w + l;
for ( ; sa.w != e; ++sa.w, ++sb.w) {
if (*sa.w != *sb.w)
return sa.w->unicode() - sb.w->unicode();
const QChar *e = a + l;
for ( ; a != e; ++a, ++b) {
if (*a != *b)
return a->unicode() - b->unicode();
}
}
return 0;