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
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Kostya Serebryany via llvm-dev
2016-Aug-12 20:57 UTC
[llvm-dev] A "hello world" coverage sanitizer
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 > >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20160812/6520f892/attachment.html>
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 >> >> >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20160812/67b96b76/attachment.html>