llvm dev - Jul 2010 - [LLVMdev] some undefined behaviors in llvm/clang

Hi folks,

Below is a short list of integer undefined behaviors executed by Clang
when compiling the LLVM test suite.  They seem pretty self explanatory,
but let me know if not, if you cannot reproduce any of them, or if it
would be better for me to file bugzillas on them.  This is on x64 Linux,
using r108984.



Thanks,





John





---------------------------------





CLANG UNDEFINED at <BitcodeWriter.cpp, (740:29)> : Op: -, Reason :
Signed Subtraction Overflow, left (int64): 0 right (int64):
-9223372036854775808

Command causing this error:



clang
-I/uusoc/exports/scratch/regehr/z/llvm-2/projects/test-suite/SingleSource/Regression/C
-I/uusoc/exports/scratch/regehr/z/llvm-2/projects/test-suite/SingleSource/Regression/C
-I/home/regehr/z/llvm-2/include
-I/home/regehr/z/llvm-2/projects/test-suite/include -I../../../include
-I/home/regehr/z/llvm-2/include -D_GNU_SOURCE -D__STDC_LIMIT_MACROS
-DNDEBUG  -O3 -mllvm -disable-llvm-optzns  -m64 -fomit-frame-pointer -c
casts.c -o Output/casts.bc -emit-llvm

---------------------------------

CLANG UNDEFINED at <InitPreprocessor.cpp, (173:39)> : Op: -, Reason :
Signed Subtraction Overflow, left (int64): -9223372036854775808 right
(int64): 1

Command causing this error:

RunToolSafely.sh 500 clang Output/sse.expandfft.cbe.c -o
Output/sse.expandfft.cbe -lm -O3 -fno-strict-aliasing -fno-inline -msse2
-m64 -fomit-frame-pointer

---------------------------------

CLANG UNDEFINED at <InstCombineCalls.cpp, (105:23)> : Op: <<, Reason
:
Unsigned Left Shift Error: Right operand is negative or is greater than
or equal to the width of the promoted left operand, left (uint32): 1
right (uint32): 63

Command causing this error:

clang
-I/uusoc/exports/scratch/regehr/z/llvm-2/projects/test-suite/MultiSource/Benchmarks/VersaBench/dbms
-I/uusoc/exports/scratch/regehr/z/llvm-2/projects/test-suite/MultiSource/Benchmarks/VersaBench/dbms
-I/home/regehr/z/llvm-2/include
-I/home/regehr/z/llvm-2/projects/test-suite/include
-I../../../../include -I/home/regehr/z/llvm-2/include -D_GNU_SOURCE
-D__STDC_LIMIT_MACROS -DNDEBUG  -O3  -c volume.c -o Output/volume.o

---------------------------------

CLANG UNDEFINED at <TargetData.cpp, (629:28)> : Op: *, Reason : Signed
Multiplication Overflow, left (int64): 142998016075267841 right (int64):
129

Command causing this error:

clang
-I/uusoc/exports/scratch/regehr/z/llvm-2/projects/test-suite/MultiSource/Benchmarks/Prolangs-C/assembler
-I/uusoc/exports/scratch/regehr/z/llvm-2/projects/test-suite/MultiSource/Benchmarks/Prolangs-C/assembler
-I/home/regehr/z/llvm-2/include
-I/home/regehr/z/llvm-2/projects/test-suite/include
-I../../../../include -I/home/regehr/z/llvm-2/include -D_GNU_SOURCE
-D__STDC_LIMIT_MACROS -DNDEBUG  -O3  -c scan_line.c -o Output/scan_line.o

---------------------------------

CLANG UNDEFINED at
</uusoc/exports/scratch/regehr/z/llvm-2/include/llvm/Instructions.h,
(233:15)> : Op: <<, Reason : Signed Left Shift Error: Right operand is
negative or is greater than or equal to the width of the promoted left
operand, left (int32): 1 right (int32): 32

Command causing this error:

clang
-I/uusoc/exports/scratch/regehr/z/llvm-2/projects/test-suite/MultiSource/Benchmarks/VersaBench/dbms
-I/uusoc/exports/scratch/regehr/z/llvm-2/projects/test-suite/MultiSource/Benchmarks/VersaBench/dbms
-I/home/regehr/z/llvm-2/include
-I/home/regehr/z/llvm-2/projects/test-suite/include
-I../../../../include -I/home/regehr/z/llvm-2/include -D_GNU_SOURCE
-D__STDC_LIMIT_MACROS -DNDEBUG  -O3  -c volume.c -o Output/volume.o

---------------------------------

Hi John,
> Below is a short list of integer undefined behaviors executed by Clang
> when compiling the LLVM test suite.  They seem pretty self explanatory,
> but let me know if not, if you cannot reproduce any of them, or if it
> would be better for me to file bugzillas on them.  This is on x64 Linux,
> using r108984.
how did you obtain this interesting info?

Thanks,

Duncan.

On Jul 28, 2010, at 6:10 AM, Duncan Sands wrote:
> Hi John,
> 
>> Below is a short list of integer undefined behaviors executed by Clang
>> when compiling the LLVM test suite.  They seem pretty self explanatory,
>> but let me know if not, if you cannot reproduce any of them, or if it
>> would be better for me to file bugzillas on them.  This is on x64
Linux,
>> using r108984.
> 
> how did you obtain this interesting info?
See also: http://blog.regehr.org/archives/226

-Chris

My student Peng Li has a hacked clang that emits checks for lots of bad 
integer behaviors.  The code still has rough edges but we'll contribute it 
soon.

John



On Wed, 28 Jul 2010, Duncan Sands wrote:
> Hi John,
>
>> Below is a short list of integer undefined behaviors executed by Clang
>> when compiling the LLVM test suite.  They seem pretty self explanatory,
>> but let me know if not, if you cannot reproduce any of them, or if it
>> would be better for me to file bugzillas on them.  This is on x64
Linux,
>> using r108984.
>
> how did you obtain this interesting info?
>
> Thanks,
>
> Duncan.
> _______________________________________________
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