On Fri, 6 Dec 2024 at 17:56, Jonathan Wakely <jwak...@redhat.com> wrote:
>
> On macOS and FreeBSD read(2) system call can return EINVAL for large
> sizes, so limit the maximum that we try to read. The calling code in
> filebuf::xsgetn will loop until it gets the size it wants, so we don't
> need to loop here.
>
> libstdc++-v3/ChangeLog:
>
> PR libstdc++/102259
> * config/io/basic_file_stdio.cc (basic_file::xsgetn): Limit n to
> INT_MAX-1 when _GLIBCXX_READ_RETURNS_EINVAL_OVER_INT_MAX is
> defined.
> * config/os/bsd/darwin/os_defines.h
> (_GLIBCXX_READ_RETURNS_EINVAL_OVER_INT_MAX):
> Define.
> * config/os/bsd/freebsd/os_defines.h
> (_GLIBCXX_READ_RETURNS_EINVAL_OVER_INT_MAX):
> Define.
> ---
>
> Any suggestions for a better name for the new macro?
>
> I haven't tested this, but I'll ask the bug submitter to do so. If they
> don't do so, I'll ask Iain or try a FreeBSD VM next week some time.
Iain and the submitter have both tested it on macOS now.
>
> libstdc++-v3/config/io/basic_file_stdio.cc | 6 ++++++
> libstdc++-v3/config/os/bsd/darwin/os_defines.h | 3 +++
> libstdc++-v3/config/os/bsd/freebsd/os_defines.h | 3 +++
> 3 files changed, 12 insertions(+)
>
> diff --git a/libstdc++-v3/config/io/basic_file_stdio.cc
> b/libstdc++-v3/config/io/basic_file_stdio.cc
> index 9b529490f08..508e2d2a469 100644
> --- a/libstdc++-v3/config/io/basic_file_stdio.cc
> +++ b/libstdc++-v3/config/io/basic_file_stdio.cc
> @@ -338,6 +338,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> if (__ret == 0 && ferror(this->file()))
> __ret = -1;
> #else
> +
> +#ifdef _GLIBCXX_READ_RETURNS_EINVAL_OVER_INT_MAX
Maybe a better design would be to define the macro to the maximum
supported value:
#ifdef _GLIBCXX_MAX_READ_SIZE
if (__builtin_expect(__n > _GLIBCXX_MAX_READ_SIZE, 0))
__n = _GLIBCXX_MAX_READ_SIZE;
#endif
> + if (__builtin_expect(__n >= __INT_MAX__, 0))
> + __n = __INT_MAX__ - 1;
> +#endif
> +
> do
> __ret = read(this->fd(), __s, __n);
> while (__ret == -1L && errno == EINTR);
> diff --git a/libstdc++-v3/config/os/bsd/darwin/os_defines.h
> b/libstdc++-v3/config/os/bsd/darwin/os_defines.h
> index 6bc7930bdba..826c863e481 100644
> --- a/libstdc++-v3/config/os/bsd/darwin/os_defines.h
> +++ b/libstdc++-v3/config/os/bsd/darwin/os_defines.h
> @@ -54,4 +54,7 @@
> // No support for referencing weak symbols without a definition.
> #define _GLIBCXX_USE_WEAK_REF 0
>
> +// read(2) can return EINVAL for n > INT_MAX.
> +#define _GLIBCXX_READ_RETURNS_EINVAL_OVER_INT_MAX 1
> +
> #endif
> diff --git a/libstdc++-v3/config/os/bsd/freebsd/os_defines.h
> b/libstdc++-v3/config/os/bsd/freebsd/os_defines.h
> index 125dfdc1888..4889bb4ec00 100644
> --- a/libstdc++-v3/config/os/bsd/freebsd/os_defines.h
> +++ b/libstdc++-v3/config/os/bsd/freebsd/os_defines.h
> @@ -50,4 +50,7 @@
> #define _GLIBCXX_USE_C99_FLOAT_TRANSCENDENTALS_DYNAMIC 0
> #endif
>
> +// read(2) can return EINVAL for n > INT_MAX.
> +#define _GLIBCXX_READ_RETURNS_EINVAL_OVER_INT_MAX 1
> +
> #endif
> --
> 2.47.1
>
