AddressSanitizer+CMake unittest question

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1

Context: I’m trying to implement support for ASan’s unittest suite in CMake. This is … quite challenging.

I think I can get it to work with one significant caveat: it will require manual dependency management. None of the automatic header tracking. I think this is fine in some cases, and not so fine in other cases. Let me explain.

It feels like these tests are really comprised of two distinct collections of tests:

  1. Those that rather directly test the ASan runtime. These do not rely upon the compiler instrumenting the code, and simply exercise the runtime library directly.
  2. Those that expect to be instrumented by the compiler, and exercise the runtime through GoogleTest’s death tests on seemingly innocuous code.

For the first bucket, there is no problem. We should be able to handle these easily.

For the second bucket, this can be a bit tricky. It requires compiling the tests with a custom compiler and flags. Let’s talk about the options for supporting this case.

A) We could require the host compiler to have support for -faddress-sanitizer, but ensure that the just-built runtime library is used rather than the host compiler’s runtime library.
B) We can depend upon the Clang built in the same LLVM/Clang/CompilerRT checkout, and provide a custom compilation strategy to use it to instrument the unittest code.

Option A has fairly obvious problems: it introduces version skew into the equation, and would require a full bootstrap to test new instrumentation. However, it plays very nicely with the build system, requiring no special magic. It also would “Just Work” in the cross-compilation scenario, as much as any unittest would.

Option B avoids any version skew issues, but at the cost of requiring us to implement a “complete” custom compilation strategy for these source files. At the very least, this will not be portable and thus will only be enabled on a few platforms, and it will not get automatic header dependency tracking.

I can pursue either of these options, but I’d like to know which the ASan folks would be most interested in working with.

Second, it would be extremely helpful to have a very firm separation between bucket #1 and bucket #2. Currently, there is one collection of tests clearly in bucket #1 (asan_noinst_test.cc), and plenty of tests clearly in bucket #2, but there seems to be quite a bit of overlap as well. For example, I would naively expect asan_interface_test.cc to not require instrumentation – it almost exclusively directly calls the runtime. But it is currently being compiled with instrumentation by the Makefile.old, so I’m at a loss. Separating these two scenarios into at least separate files, and ideally linking them into two separate binaries would make everything much simpler. For example, bucket #2 shouldn’t need to include any of ASan’s header files, making it easier to manage manual dependencies if necessary.

2

Hi CMake’ers,

See the email below from llvmdev. I was wondering whether there’s a better way to solve this. Ideas?

Thanks!
/Manuel

3

FWIW, I’ve started implementing this and folks can try it out as of r159134.

The way to test out the current CMake build is to comment out the exclusion of ‘compiler-rt’ from the LLVM build in ‘projects/CMakeLists.txt’. Then you can build, for example ‘make AsanTests’ and it should compile both the instrumented and non-instrumented unit tests.

Currently, you have to run them by hand – I need to refactor a bit of the LLVM cmake build before i can wire in nice convenience targets for running these – but I’ve tried and they seem to work for me…

4

Context: I’m trying to implement support for ASan’s unittest suite in CMake. This is … quite challenging.

I think I can get it to work with one significant caveat: it will require manual dependency management. None of the automatic header tracking. I think this is fine in some cases, and not so fine in other cases. Let me explain.

It feels like these tests are really comprised of two distinct collections of tests:

  1. Those that rather directly test the ASan runtime. These do not rely upon the compiler instrumenting the code, and simply exercise the runtime library directly.
  2. Those that expect to be instrumented by the compiler, and exercise the runtime through GoogleTest’s death tests on seemingly innocuous code.

For the first bucket, there is no problem. We should be able to handle these easily.

For the second bucket, this can be a bit tricky. It requires compiling the tests with a custom compiler and flags. Let’s talk about the options for supporting this case.

A) We could require the host compiler to have support for -faddress-sanitizer, but ensure that the just-built runtime library is used rather than the host compiler’s runtime library.
B) We can depend upon the Clang built in the same LLVM/Clang/CompilerRT checkout, and provide a custom compilation strategy to use it to instrument the unittest code.

Option A has fairly obvious problems: it introduces version skew into the equation, and would require a full bootstrap to test new instrumentation. However, it plays very nicely with the build system, requiring no special magic. It also would “Just Work” in the cross-compilation scenario, as much as any unittest would.

Option B avoids any version skew issues, but at the cost of requiring us to implement a “complete” custom compilation strategy for these source files. At the very least, this will not be portable and thus will only be enabled on a few platforms, and it will not get automatic header dependency tracking.

I can pursue either of these options, but I’d like to know which the ASan folks would be most interested in working with.

Second, it would be extremely helpful to have a very firm separation between bucket #1 and bucket #2.

(answering parts at a time)
Agree. I am going to fix that now.

5

Context: I’m trying to implement support for ASan’s unittest suite in CMake. This is … quite challenging.

I think I can get it to work with one significant caveat: it will require manual dependency management. None of the automatic header tracking. I think this is fine in some cases, and not so fine in other cases. Let me explain.

It feels like these tests are really comprised of two distinct collections of tests:

  1. Those that rather directly test the ASan runtime. These do not rely upon the compiler instrumenting the code, and simply exercise the runtime library directly.
  2. Those that expect to be instrumented by the compiler, and exercise the runtime through GoogleTest’s death tests on seemingly innocuous code.

For the first bucket, there is no problem. We should be able to handle these easily.

For the second bucket, this can be a bit tricky. It requires compiling the tests with a custom compiler and flags. Let’s talk about the options for supporting this case.

A) We could require the host compiler to have support for -faddress-sanitizer, but ensure that the just-built runtime library is used rather than the host compiler’s runtime library.
B) We can depend upon the Clang built in the same LLVM/Clang/CompilerRT checkout, and provide a custom compilation strategy to use it to instrument the unittest code.

Option A has fairly obvious problems: it introduces version skew into the equation, and would require a full bootstrap to test new instrumentation. However, it plays very nicely with the build system, requiring no special magic. It also would “Just Work” in the cross-compilation scenario, as much as any unittest would.

Option B avoids any version skew issues, but at the cost of requiring us to implement a “complete” custom compilation strategy for these source files. At the very least, this will not be portable and thus will only be enabled on a few platforms, and it will not get automatic header dependency tracking.

B is highly preferable.
I.e.:

  1. Build clang
  2. Build asan-rt (doesn’t not matter with which compiler)
  3. build asan-rt-tests using clang from #1
    This is what we use now anyway.
    There could of course be dependencies between asan-rt and asan-rt-tests, but even worth, there could be dependencies between the instrumentation module in LLVM and asan-rt-tests.

I can pursue either of these options, but I’d like to know which the ASan folks would be most interested in working with.

Second, it would be extremely helpful to have a very firm separation between bucket #1 and bucket #2.

(answering parts at a time)
Agree. I am going to fix that now.

This part is fixed by r159135.

thanks!!

–kcc

6

Ok... :: sigh :: Have to go and make this hard on me.

An additional constraint that would make this slightly easier: for the
tests which require instrumentation, could they strictly avoid
including headers outside of the test-helper headers? That is, none of
the libasan headers themselves.

This would make dependency management much much simpler, which seems
important given that it must be done manually.

7

Context: I’m trying to implement support for ASan’s unittest suite in CMake. This is … quite challenging.

I think I can get it to work with one significant caveat: it will require manual dependency management. None of the automatic header tracking. I think this is fine in some cases, and not so fine in other cases. Let me explain.

It feels like these tests are really comprised of two distinct collections of tests:

  1. Those that rather directly test the ASan runtime. These do not rely upon the compiler instrumenting the code, and simply exercise the runtime library directly.
  2. Those that expect to be instrumented by the compiler, and exercise the runtime through GoogleTest’s death tests on seemingly innocuous code.

For the first bucket, there is no problem. We should be able to handle these easily.

For the second bucket, this can be a bit tricky. It requires compiling the tests with a custom compiler and flags. Let’s talk about the options for supporting this case.

A) We could require the host compiler to have support for -faddress-sanitizer, but ensure that the just-built runtime library is used rather than the host compiler’s runtime library.
B) We can depend upon the Clang built in the same LLVM/Clang/CompilerRT checkout, and provide a custom compilation strategy to use it to instrument the unittest code.

Option A has fairly obvious problems: it introduces version skew into the equation, and would require a full bootstrap to test new instrumentation. However, it plays very nicely with the build system, requiring no special magic. It also would “Just Work” in the cross-compilation scenario, as much as any unittest would.

Option B avoids any version skew issues, but at the cost of requiring us to implement a “complete” custom compilation strategy for these source files. At the very least, this will not be portable and thus will only be enabled on a few platforms, and it will not get automatic header dependency tracking.

B is highly preferable.
I.e.:

  1. Build clang
  2. Build asan-rt (doesn’t not matter with which compiler)
  3. build asan-rt-tests using clang from #1
    This is what we use now anyway.
    There could of course be dependencies between asan-rt and asan-rt-tests, but even worth, there could be dependencies between the instrumentation module in LLVM and asan-rt-tests.

Ok… :: sigh :: Have to go and make this hard on me.

An additional constraint that would make this slightly easier: for the
tests which require instrumentation, could they strictly avoid
including headers outside of the test-helper headers? That is, none of
the libasan headers themselves.

Um, I guess so. AFAIR, it is true even now. I assume, including gtest headers is a
separate problem?

8

I can make that work through dirty dirty hacks. The various different
sanitizer runtimes are actually harder to track and predict.

9

And one more question regarding ASan cmake build.
Currently unittests are fine, but regular “clang -faddress-sanitizer” is not:

current cmake build stores libclang_rt.asan-x86_64.a together with all the LLVM libs
(in $build_path/lib/libclang_rt.asan-x86_64.a), but the Clang driver looks for asan runtime
in clang resource dir: $build_path/lib/clang/3.2/lib/linux/libclang_rt.asan-x86_64.a). I can
try to find a way to how this can be fixed, but probably you can tell the answer right away.

10

And one more question regarding ASan cmake build.
Currently unittests are fine, but regular “clang -faddress-sanitizer” is not:

As a side note: I don’t like that the current cmake machinery builds asan tests by explicitly passing libclang_rt.asan-x86_64.a.
IMO it needs to use “clang -faddress-sanitizer”.

–kcc

11

Why?

These are internal tests, and I think it is reasonable to use internal
implementation details to make them work.

I'm not saying we can't get there, I think we can, but I think it may be
somewhat more annoying than you might imagine to get there in the short
term.

12

This complicates the maintenance (if we change the path where libclang_rt.asan-x86_64.a resides we’’ have to change it in two places).
But as long as at least some tests actually use “clang -faddress-sanitizer”, it’s not that critical if other tests use libclang_rt.asan-x86_64.a

–kcc