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Re: [csmith-dev] Using safe math headers in csmith

Hi John

I was testing csmith the macro options; however, when running on a large population of seed, we got testcases with a different output when using macros.

I debugged it a bit, and it is due to 3 main issues: (1) safe condition checks are not always the same, (2) casting (between explicit C-like casting in the macros and implicit casting coming from the function signature), and last (3) brackets. 

I can relatively easily fix 2+3, however (1) tends to be a bit more tricky.

For example:
The seed: 314862222 produces a different result when using macros due to differences in the conditions (the ternary operator) in rshift_func_int8_t_s_u.

I compile it and run it that way: 
./src/csmith --seed 314862222 --bitfields --packed-struct >> temp_regular_5.c
clang -I../runtimeExp -DUSE_MATH_MACROS -w -O temp_regular_5.c -o temp_macros_5

The conditions:
((left < 0) || (((unsigned int)right) >= 32)) vs. (((int8_t)(left)) < ((int8_t)0)) || (((unsigned int)(right)) >= sizeof(int8_t)*CHAR_BIT)); these are evaluated to false vs. true for seed 314862222.

Please let me know if more examples of seeds could help. I have several examples.

Thanks much,


-----Original Message-----
From: csmith-dev-bounces@flux.utah.edu <csmith-dev-bounces@flux.utah.edu> On Behalf Of John Regehr
Sent: 24 February 2020 18:01
To: csmith-dev@flux.utah.edu
Subject: Re: [csmith-dev] Using safe math headers in csmith

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Hi Karine, ok, I looked into this. Both of these alternative header files appear to work just fine. If you want to use the NOTMP versions, you need to pass Csmith the additional --math-notmp flag.

I ran this shell script a few times and both versions always produced the same checksum:

./src/csmith > foo.c
clang -O0 -w foo.c -I../runtime -o foo1
clang -O0 foo.c -I../runtime -DUSE_MATH_MACROS -w -o foo2 ulimit -t 2

Let us know if anything doesn't work as advertised.


On 2/24/20 8:20 AM, John Regehr wrote:
> Hi Karine,
> Well, I just tried to compile a program using -DUSE_MATH_MACROS_NOTMP 
> and it did not compile, so something must have gone wrong here. I 
> assume the same thing happened when you tried this?
> I'll try to look into it soon.
> John
> On 2/24/20 2:28 AM, Even Mendoza, Karine wrote:
>> Hi,
>> I would like to know if the version of csmith using the header 
>> safe_math_macros.h or safe_math_macros_notmp.c is working.
>> Can I use these headers instead of safe_math.h and expect the same 
>> output for the generated programs?
>> Thanks much,
>> Karine