On Mon, Mar 31, 2025 at 6:23 PM Jonathan Wakely <jwak...@redhat.com> wrote:
> This is yet another false positive warning fix. This time the compiler
> can't prove that when the vector has sufficient excess capacity to
> append new elements, the pointer to the existing storage is not null.
>
> libstdc++-v3/ChangeLog:
>
> PR libstdc++/114945
> * include/bits/vector.tcc (vector::_M_default_append): Add
> unreachable condition so the compiler knows that _M_finish is
> not null.
> * testsuite/23_containers/vector/capacity/114945.cc: New test.
> ---
>
> Tested x86_64-linux.
>
LGTM
>
> libstdc++-v3/include/bits/vector.tcc | 3 ++
> .../23_containers/vector/capacity/114945.cc | 36 +++++++++++++++++++
> 2 files changed, 39 insertions(+)
> create mode 100644
> libstdc++-v3/testsuite/23_containers/vector/capacity/114945.cc
>
> diff --git a/libstdc++-v3/include/bits/vector.tcc
> b/libstdc++-v3/include/bits/vector.tcc
> index 7a92f34ec64..66d73b4cfd7 100644
> --- a/libstdc++-v3/include/bits/vector.tcc
> +++ b/libstdc++-v3/include/bits/vector.tcc
> @@ -768,6 +768,9 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
>
> if (__navail >= __n)
> {
> + if (!this->_M_impl._M_finish)
> + __builtin_unreachable();
> +
> _GLIBCXX_ASAN_ANNOTATE_GROW(__n);
> this->_M_impl._M_finish =
> std::__uninitialized_default_n_a(this->_M_impl._M_finish,
> diff --git
> a/libstdc++-v3/testsuite/23_containers/vector/capacity/114945.cc
> b/libstdc++-v3/testsuite/23_containers/vector/capacity/114945.cc
> new file mode 100644
> index 00000000000..daafc59d5a9
> --- /dev/null
> +++ b/libstdc++-v3/testsuite/23_containers/vector/capacity/114945.cc
> @@ -0,0 +1,36 @@
> +// { dg-options "-O2 -Werror=stringop-overflow -Werror=array-bounds" }
> +// { dg-do compile { target c++11 } }
> +
> +// Bug libstdc++/114945
> +// Sporadic std::vector::resize() -Wstringop-overflow or -Warray-bounds
> warning
> +
> +#include <stdint.h>
> +#include <vector>
> +template <typename a> struct b {
> + void resize(std::size_t c) { d.resize(c); }
> + template <typename e> void f(a, e);
> + std::vector<char> d;
> +};
> +#include <regex>
> +std::regex g;
> +uint64_t h;
> +uint32_t i;
> +struct s {
> + enum class j : size_t;
> + void k();
> + using l = b<j>;
> + std::vector<l> m;
> +};
> +enum class s::j : size_t { n };
> +void o() { g = ""; }
> +void s::k() {
> + l p;
> + auto q = uint32_t(), r = uint32_t();
> + if (h)
> + r = i;
> + b<size_t> t;
> + if (q || r)
> + p.f(j::n, 5);
> + t.resize(4);
> + m.push_back(p);
> +}
> --
> 2.49.0
>
>
