[PATCH] PR libstdc++/89446 fix null pointer dereference in char_traits

[Jakub Jelinek]

On Sat, Feb 23, 2019 at 01:02:20AM +0000, Jonathan Wakely wrote:
> 	PR libstdc++/89446
> 	* include/bits/char_traits.h (__constant_char_array): Check index is
> 	in range before dereferencing.
> 	* testsuite/21_strings/basic_string_view/operators/char/89446.cc:
> 	New test.
> 
> Tested x86_64-linux, committed to gcc-8-branch and gcc-7-branch.

And not trunk?  The bug is still there, even when it should be usually
ifdefed out because __builtin_is_constexpr_evaluated() should be supported.

> commit b639a9cac6e2532eb852b03df6ac40d34f1dd28c
> Author: Jonathan Wakely <jwakely@redhat.com>
> Date:   Fri Feb 22 20:33:16 2019 +0000
> 
>     PR libstdc++/89446 fix null pointer dereference in char_traits
>     
>             PR libstdc++/89446
>             * include/bits/char_traits.h (__constant_char_array): Check index is
>             in range before dereferencing.
>             * testsuite/21_strings/basic_string_view/operators/char/89446.cc:
>             New test.
> 
> diff --git a/libstdc++-v3/include/bits/char_traits.h b/libstdc++-v3/include/bits/char_traits.h
> index 1945494d7e2..a2a883f3565 100644
> --- a/libstdc++-v3/include/bits/char_traits.h
> +++ b/libstdc++-v3/include/bits/char_traits.h
> @@ -248,7 +248,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>      __constant_char_array_p(const _CharT* __a, size_t __n)
>      {
>        size_t __i = 0;
> -      while (__builtin_constant_p(__a[__i]) && __i < __n)
> +      while (__i < __n && __builtin_constant_p(__a[__i]))
>  	__i++;
>        return __i == __n;
>      }

	Jakub