[PATCH] Support/Unix: use lambda function to fix building errors with clang

[Pavel Labath via llvm-commits]

I think all/most systems have open(2) defined as a variadic (...)
function, so that can't be the only reason why this is failing for
you. There must be something more which is specific to your platform.
Nevertheless, the workaround is not bad, so there's no harm in
changing this. Some people would even prefer the lambda based syntax.
On Sun, 8 Jul 2018 at 21:28, Mauro Rossi <issor.oruam at gmail.com> wrote:
>
> From: Chih-Wei Huang <cwhuang at linux.org.tw>
>
> The ::open() function has unlimited arguments. Seems the compiler can't
> infer the template argument from it:
>
> external/llvm70/lib/Support/Unix/Path.inc:770:19: error: no matching function for call to 'RetryAfterSignal'
>   if ((ResultFD = sys::RetryAfterSignal(-1, ::open, P.begin(), OpenFlags, Mode)) <
>                   ^~~~~~~~~~~~~~~~~~~~~
> external/llvm70/lib/Support/../../include/llvm/Support/Errno.h:34:13: note: candidate template ignored: couldn't infer template argument 'Fun'
> inline auto RetryAfterSignal(const FailT &Fail, const Fun &F,
>             ^
> 1 error generated.
>
> To avoid that, use a lambda function to wrap the ::open() function.
> ---
>  lib/Support/Unix/Path.inc    | 4 ++--
>  lib/Support/Unix/Process.inc | 2 +-
>  2 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/lib/Support/Unix/Path.inc b/lib/Support/Unix/Path.inc
> index b8fea5bda4f..44a8b981c48 100644
> --- a/lib/Support/Unix/Path.inc
> +++ b/lib/Support/Unix/Path.inc
> @@ -766,8 +766,8 @@ std::error_code openFile(const Twine &Name, int &ResultFD,
>
>    SmallString<128> Storage;
>    StringRef P = Name.toNullTerminatedStringRef(Storage);
> -  if ((ResultFD = sys::RetryAfterSignal(-1, ::open, P.begin(), OpenFlags, Mode)) <
> -      0)
> +  auto openfun([&] { return ::open(P.begin(), OpenFlags, Mode); });
> +  if ((ResultFD = sys::RetryAfterSignal(-1, openfun)) < 0)
>      return std::error_code(errno, std::generic_category());
>  #ifndef O_CLOEXEC
>    if (!(Flags & OF_ChildInherit)) {
> diff --git a/lib/Support/Unix/Process.inc b/lib/Support/Unix/Process.inc
> index fa515d44f3f..1111cd2fe2c 100644
> --- a/lib/Support/Unix/Process.inc
> +++ b/lib/Support/Unix/Process.inc
> @@ -211,7 +211,7 @@ std::error_code Process::FixupStandardFileDescriptors() {
>      assert(errno == EBADF && "expected errno to have EBADF at this point!");
>
>      if (NullFD < 0) {
> -      if ((NullFD = RetryAfterSignal(-1, ::open, "/dev/null", O_RDWR)) < 0)
> +      if ((NullFD = RetryAfterSignal(-1, [] { return ::open("/dev/null", O_RDWR); })) < 0)
>          return std::error_code(errno, std::generic_category());
>      }
>
> --
> 2.17.1
>