False positive for interation of counter with addition and multiplication of self #11653
Description
| Bugzilla Link | 11281 |
| Version | unspecified |
| OS | All |
| Reporter | LLVM Bugzilla Contributor |
| CC | @efriedma-quic |
Extended Description
The following code is from the leveldb project.
bool ConsumeDecimalNumber(Slice* in, uint64_t* val) {
uint64_t v = 0;
int digits = 0;
while (!in->empty()) {
char c = (*in)[0];
if (c >= '0' && c <= '9') {
++digits;
const int delta = (c - '0');
static const uint64_t kMaxUint64 = ~static_cast<uint64_t>(0);
if (v > kMaxUint64/10 ||
(v == kMaxUint64/10 && delta > kMaxUint64%10)) {
// Overflow
return false;
}
v = (v * 10) + delta;
in->remove_prefix(1);
} else {
break;
}
}
*val = v;
return (digits > 0);
}
When using Analyze in Xcode, the following result is reported:
Analyze leveldb/util/logging.cc
cd /Users/bgulanowski/Dev/Nulayer/NULevelDB
setenv LANG en_US.US-ASCII
setenv PATH "/Developer/Platforms/iPhoneSimulator.platform/Developer/usr/bin:/Developer/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin"
/Developer/usr/bin/clang -x c++ -arch i386 -fmessage-length=0 -fdiagnostics-print-source-range-info -fdiagnostics-show-category=id -fdiagnostics-parseable-fixits -Wno-trigraphs -fpascal-strings -O0 -Wreturn-type -Wparentheses -Wswitch -Wno-unused-parameter -Wunused-variable -Wunused-value -Wno-shorten-64-to-32 -Wc++0x-extensions -DDEBUG=1 -isysroot /Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator5.0.sdk -fexceptions -fasm-blocks -mmacosx-version-min=10.6 -gdwarf-2 -Wno-sign-conversion -D__IPHONE_OS_VERSION_MIN_REQUIRED=40300 -iquote /Users/Shared/bgulanowski/Developer/Intermediates/NULevelDB.build/Debug-iphonesimulator/leveldb.build/leveldb-generated-files.hmap -I/Users/Shared/bgulanowski/Developer/Intermediates/NULevelDB.build/Debug-iphonesimulator/leveldb.build/leveldb-own-target-headers.hmap -I/Users/Shared/bgulanowski/Developer/Intermediates/NULevelDB.build/Debug-iphonesimulator/leveldb.build/leveldb-all-target-headers.hmap -iquote /Users/Shared/bgulanowski/Developer/Intermediates/NULevelDB.build/Debug-iphonesimulator/leveldb.build/leveldb-project-headers.hmap -iquote/Users/bgulanowski/Dev/Nulayer/NULevelDB/leveldb/include -iquote/Users/bgulanowski/Dev/Nulayer/NULevelDB/leveldb -I/Users/Shared/bgulanowski/Developer/Products/Debug-iphonesimulator/include -I/Users/Shared/bgulanowski/Developer/Intermediates/NULevelDB.build/Debug-iphonesimulator/leveldb.build/DerivedSources/i386 -I/Users/Shared/bgulanowski/Developer/Intermediates/NULevelDB.build/Debug-iphonesimulator/leveldb.build/DerivedSources -F/Users/Shared/bgulanowski/Developer/Products/Debug-iphonesimulator -DOS_MACOSX -DLEVELDB_PLATFORM_POSIX -MMD -MT dependencies -MF /Users/Shared/bgulanowski/Developer/Intermediates/NULevelDB.build/Debug-iphonesimulator/leveldb.build/StaticAnalyzer/normal/i386/logging.d --analyze /Users/bgulanowski/Dev/Nulayer/NULevelDB/leveldb/util/logging.cc -o /Users/Shared/bgulanowski/Developer/Intermediates/NULevelDB.build/Debug-iphonesimulator/leveldb.build/StaticAnalyzer/normal/i386/logging.plist
/Users/bgulanowski/Dev/Nulayer/NULevelDB/leveldb/util/logging.cc:71:22:{71:20-71:21}: warning: The left operand to '*' is always 0
v = delta + (v * 10);
~ ^
/Users/bgulanowski/Dev/Nulayer/NULevelDB/leveldb/util/logging.cc:71:17:{71:19-71:27}: warning: The right operand to '+' is always 0
v = delta + (v * 10);
^ ~~~~~~~~
2 warnings generated.
If you wish, you may download NULevelDB from github and run the Analyzer on that.
As far as I can tell, delta is > 0 if c is > '0', so v is not always zero.
Thanks for your awesome work, you people are amazing.
Cheers,
Brent Gulanowski
This is for version 3.0 of clang. At least, that's what it output in Terminal. I am using Xcode 4.2 for Lion.