[libcxx] r222052 - Initialize pointer in string conversion helpers to prevent MSAN diagnostic.

[Kostya Serebryany]

if msan does not see what's goign on inside libc we need to teach it -- it
already has a bunch of libc interceptors, but clearly not all.
Do you know what libc function is called here?
Or how to reproduce the reports you've been seeing?

On Fri, Nov 14, 2014 at 2:23 PM, Eric Fiselier <eric at efcs.ca> wrote:

> Author: ericwf
> Date: Fri Nov 14 16:23:57 2014
> New Revision: 222052
>
> URL: http://llvm.org/viewvc/llvm-project?rev=222052&view=rev
> Log:
> Initialize pointer in string conversion helpers to prevent MSAN diagnostic.
>
> Since the initialization of the pointer happens across the libc library
> boundry
> MSAN will not know the pointer was initialized. This fixes MSAN failures in
> test/strings/string.conversions.
>
> Modified:
>     libcxx/trunk/src/string.cpp
>
> Modified: libcxx/trunk/src/string.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/libcxx/trunk/src/string.cpp?rev=222052&r1=222051&r2=222052&view=diff
>
> ==============================================================================
> --- libcxx/trunk/src/string.cpp (original)
> +++ libcxx/trunk/src/string.cpp Fri Nov 14 16:23:57 2014
> @@ -63,7 +63,7 @@ inline
>  V
>  as_integer_helper(const string& func, const S& str, size_t* idx, int
> base, F f)
>  {
> -    typename S::value_type* ptr;
> +    typename S::value_type* ptr = nullptr;
>      const typename S::value_type* const p = str.c_str();
>      typename remove_reference<decltype(errno)>::type errno_save = errno;
>      errno = 0;
> @@ -180,7 +180,7 @@ inline
>  V
>  as_float_helper(const string& func, const S& str, size_t* idx, F f )
>  {
> -    typename S::value_type* ptr;
> +    typename S::value_type* ptr = nullptr;
>      const typename S::value_type* const p = str.c_str();
>      typename remove_reference<decltype(errno)>::type errno_save = errno;
>      errno = 0;
>
>
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