[llvm-dev] A "hello world" coverage sanitizer

[Kostya Serebryany via llvm-dev]

I did mean trace-pc.
trace-bb inserts callbacks to the existing run-time function that does some
bookkeeping; you can not (easily) redefine it.
trace-pc inserts callbacks to user-defined functions -- you can implement
those functions to do whatever you need to.

--kcc

On Fri, Aug 12, 2016 at 7:40 PM, Zhoulai <zell08v at gmail.com> wrote:

> Thank you, kcc. I am unsure if I misunderstand your reply. It seems that
> trace-bb, rather than trace-pc,  fits better for my problem, given that my
> instrumentation is to put before each conditional statement. Do I
> misunderstand something here?
>
>  "
> Tracing basic blocks
> <http://clang.llvm.org/docs/SanitizerCoverage.html#id11>
> With -fsanitize-coverage=trace-bb the compiler will insert
> __sanitizer_cov_trace_basic_block(s32 *id) before every function, basic
> block, or edge (depending on the value of -fsanitize-coverage=[func,bb,
> edge]).
> "
>
>
> *Thanks,*
>
> *Zhoulai*
>
>
>
>
>
> Zhoulai
>
> On Fri, Aug 12, 2016 at 1:57 PM, Kostya Serebryany <kcc at google.com> wrote:
>
>> Hi Zhoulai,
>> The closest you can get is http://clang.llvm.org/docs/
>> SanitizerCoverage.html#tracing-pcs
>> With this flavor of instrumentation the compiler inserts calls to
>> __sanitizer_cov_trace_pc into the control flow.
>> The users (you) needs to define the function __sanitizer_cov_trace_pc and
>> so you can call printf there.
>>
>> By default, not all edges in the control flow are instrumented
>> This is an optimization, you can disable it by -mllvm
>> -sanitizer-coverage-prune-blocks=0
>>
>> --kcc
>>
>> On Fri, Aug 12, 2016 at 11:46 AM, Zhoulai via llvm-dev <
>> llvm-dev at lists.llvm.org> wrote:
>>
>>> Hi, all
>>>
>>> I want to instrument a program automatically so that it prints "hello"
>>> before each conditional statement. For example, consider the function P
>>> below.
>>>
>>>     int P(int x) {
>>>      if (x<3)
>>>         if (x>0)
>>>            return 1;
>>>      return 0;
>>>    }
>>>
>>> Let P_instrum be the instrumented version of P.  It is expected that:
>>>
>>> -- P_instrum(1)  prints two "hello"s
>>> -- P_instrum(-1) prints one "hello"
>>> -- P_instrum(5)  prints no "hello"
>>>
>>> From my understanding about Clang's sanitizer coverage,
>>> <http://clang.llvm.org/docs/SanitizerCoverage.html> we can use a
>>> sanitizer to achieve this instrumentation.  However, so far I have not
>>> found a working example or snippet code to get started. Any idea?
>>>
>>> Thanks,
>>>
>>> Zhoulai
>>>
>>> _______________________________________________
>>> LLVM Developers mailing list
>>> llvm-dev at lists.llvm.org
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>
>>>
>>
>
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