[PATCH] Adding ASAN support for libc++'s vector

[Marshall Clow]

On May 7, 2014, at 12:25 AM, Kostya Serebryany <kcc at google.com> wrote:
> On Wed, May 7, 2014 at 1:05 AM, Marshall Clow <mclow.lists at gmail.com> wrote:
> Address sanitizer does not currently check for accesses beyond the end of a vector, but within the memory block managed by the vector.
> 
> For example:
>         vector<int> v;
>         v.reserve(10); // make space for 10 elements, but vector is still empty
>         cout << v[1]; // access outside the “valid elements” of the vector.
> 
> This patch adds the ability to detect these kinds of errors to libc++ when using Address Sanitizer.
> Thanks to Kostya for most of the code here.
> 
> Looks great, ship it! 
> 
> Few minor comments below. 
> 
> +++ include/__config    (working copy)
> +#ifndef _LIBCPP_HAS_NO_ASAN
> 
> Do you prefer double-negative statements? 
> #ifdef _LIBCPP_HAS_ASAN
> might be easier to read, but that's not critical. 

The reason is that this way you can turn on address sanitizer in your project, but still disable ASAN in libc++ if you want
by adding "-D _LIBCPP_HAS_NO_ASAN=1 “ to the command line.

> +++ test/containers/sequences/vector/asan.pass.cpp      (working copy)
> +#ifndef _LIBCPP_HAS_NO_ASAN
> +extern "C" void __asan_set_error_exit_code(int);
> 
> +++ test/support/asan_testing.h (working copy)
> +#ifndef _LIBCPP_HAS_NO_ASAN
> +extern "C" int __sanitizer_verify_contiguous_container
> +     ( const void *beg, const void *mid, const void *end );
> 
> I understand the desire to not incluide <sanitizer/asan_interface.h> in include/__config,
> but why not include it in the test files? 

Because I didn’t want to add an external dependency to the libc++ test suite.
Interestingly enough, people are using the libc++ test suite on other compilers than clang,
and on other standard library implementations, too.

Is that the right path when using GCC as well?


> +++ test/containers/sequences/vector/asan.pass.cpp      (working copy)
> +#if __cplusplus >= 201103L
> +    {
> +        typedef int T;
> +        typedef std::vector<T, min_allocator<T>> C;
> +        const T t[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
> +        C c(std::begin(t), std::end(t));
> +        c.reserve(2*c.size());
> +        T foo = c[c.size()];    // bad, but not caught by ASAN
> +    }
> +#endif
> 
> Maybe add a comment explaining why ASAN does not catch it
> (because asan can't handle arbitrary allocator)?

Can do.

— Marshall

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