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Re: [csmith-dev] Some random questions

     I learnt from "scripts/compiler_test.pl <http://compiler_test.pl>"
that, a wrong code bug is determined by comparing the checksum output
value generated across
     different optimization levels. So if a compiler wrong-code bug
exists across all optimization, how do i find it?

Bugs where a compiler emits the same wrong code at all optimization levels are easy to find: you just need to include two independently developed compilers in the set of compilers to test. We often test Clang against GCC. Since most compiler bugs are in the optimizers, it is quite uncommon to find these bugs. But it happens.

2. Suppose if set "bitfields_creation_prob=100" (100% probability?) in
my configuration file and use it to generate a testcase, should the
     testcase contain atleast one bitfield structure in it? For me,
setting "bitfields_creation_prob=100" didn't create any testcase with
bitfield in it. i'm bit
     unclear about

It does not mean that your program will always contain bitfields. Yang can explain the probability file more, but please do not consider these to be a well-supported feature of Csmith.

If you want programs that always contain bitfields, you should generate a lot of programs and filter out the ones you do not want.

3. What is the the ideal timeout value for csmith to generate a
testcase. Can i consider $CSMITH_TIMEOUT = 90; itself? or it may take
more than that also?

In my experience it can take longer than any timeout :). 90 seconds is probably fine.

4. I'm not able to understand some of the statistics generated at the
end of each test case. i.e.
         XXX max struct depth: 1
        depth: 0, occurrence: 412
        depth: 1, occurrence: 37

        XXX max expression depth: 2
        depth: 0, occurrence: 417
        depth: 1, occurrence: 35
        depth: 2, occurrence: 2

Xuejun will have to explain this.