[lldb] Fix 'ptsname_r' is only available on macOS 10.13.4 or newer

[JDevlieghere]

Summary

A deployment target that's less than 10.13.4 causes an error saying that 'ptsname_r' is only available on macOS 10.13.4 or newer. The current logic only checks if the symbol is available and doesn't account for the deployment target. This patch fixes that.

[mib]

LGTM

[qram9]

Hi there,

This change has caused the following warning:

llvm-project/lldb/source/Host/common/PseudoTerminal.cpp:106:20: error: unused function 'use_ptsname' [-Werror,-Wunused-function] static std::string use_ptsname(int fd) { ^

1 error generated.

The build compiler is clang++-12 on Ubuntu- 12.10.

Would you kindly look this over to add a fix?

Best,
Ram

PS:
Exact Build command:
/usr/bin/clang++ -DHAVE_ROUND -DLLDB_CONFIGURATION_DEBUG -D_DEBUG -D_GNU_SOURCE -DSTDC_CONSTANT_MACROS -DSTDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/mnt/vss/_work/1/b/llvm/Debug/tools/lldb/source/Host -I/mnt/vss/_work/1/llvm-project/lldb/source/Host -I/mnt/vss/_work/1/llvm-project/lldb/include -I/mnt/vss/_work/1/b/llvm/Debug/tools/lldb/include -I/mnt/vss/_work/1/b/llvm/Debug/include -I/mnt/vss/_work/1/llvm-project/llvm/include -I/mnt/vss/_work/1/llvm-project/llvm/../clang/include -I/mnt/vss/_work/1/b/llvm/Debug/tools/lldb/../clang/include -I/mnt/vss/_work/1/llvm-project/lldb/source -I/mnt/vss/_work/1/b/llvm/Debug/tools/lldb/source -isystem /usr/include/libxml2 -fPIC -fvisibility-inlines-hidden -Werror -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -pedantic -Wno-long-long -Wc++98-compat-extra-semi -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wmisleading-indentation -fdiagnostics-color -Wno-deprecated-declarations -Wno-unknown-pragmas -Wno-strict-aliasing -Wno-deprecated-register -Wno-vla-extension -g -fno-exceptions -gsplit-dwarf -std=c++14 -MD -MT tools/lldb/source/Host/CMakeFiles/lldbHost.dir/common/PseudoTerminal.cpp.o -MF tools/lldb/source/Host/CMakeFiles/lldbHost.dir/common/PseudoTerminal.cpp.o.d -o tools/lldb/source/Host/CMakeFiles/lldbHost.dir/common/PseudoTerminal.cpp.o -c /mnt/vss/_work/1/llvm-project/lldb/source/Host/common/PseudoTerminal.cpp

[JDevlieghere]

I was about to push a fix but it seems like it was already fixed by:

commit 4391625255c62074037d95a55232a87eae70c60b
Author: Kazu Hirata <[e-mail]>
Date:   Wed May 25 09:49:05 2022 -0700

    [lldb] Fix an unused function warning

    This patch fixes:

      .../llvm-project/lldb/source/Host/common/PseudoTerminal.cpp:106:20:
      error: unused function 'use_ptsname' [-Werror,-Wunused-function]

lldb/source/Host/common/PseudoTerminal.cpp

 #include <cstring>
 #include <mutex>
 #if defined(TIOCSCTTY)
 #include <sys/ioctl.h>
 #endif
 
 #include "lldb/Host/PosixApi.h"
 
+#if defined(__APPLE__)
+#include <Availability.h>
+#endif
+
 #if defined(__ANDROID__)
 int posix_openpt(int flags);
 #endif
 
 using namespace lldb_private;
 
 // PseudoTerminal constructor
 PseudoTerminal::PseudoTerminal() = default;
llvm::Error PseudoTerminal::OpenSecondary(int oflag) {
   m_secondary_fd = llvm::sys::RetryAfterSignal(-1, ::open, name.c_str(), oflag);
   if (m_secondary_fd >= 0)
     return llvm::Error::success();
 
   return llvm::errorCodeToError(
       std::error_code(errno, std::generic_category()));
 }
 
+static std::string use_ptsname(int fd) {
+  static std::mutex mutex;
+  std::lock_guard<std::mutex> guard(mutex);
+  const char *r = ptsname(fd);
+  assert(r != nullptr);
+  return r;
+}
+
 std::string PseudoTerminal::GetSecondaryName() const {
   assert(m_primary_fd >= 0);
 #if HAVE_PTSNAME_R
+#if defined(__APPLE__)
+  if (__builtin_available(macos 10.13.4, iOS 11.3, tvOS 11.3, watchOS 4.4, *)) {
+#endif
     char buf[PATH_MAX];
     buf[0] = '\0';
     int r = ptsname_r(m_primary_fd, buf, sizeof(buf));
     (void)r;
     assert(r == 0);
     return buf;
+#if defined(__APPLE__)
+  } else {
+    return use_ptsname(m_primary_fd);
+  }
+#endif
 #else
-  static std::mutex mutex;
-  std::lock_guard<std::mutex> guard(mutex);
-  const char *r = ptsname(m_primary_fd);
-  assert(r != nullptr);
-  return r;
+  return use_ptsname(m_primary_fd);
 #endif
 }
 
 llvm::Expected<lldb::pid_t> PseudoTerminal::Fork() {
 #if LLDB_ENABLE_POSIX
   if (llvm::Error Err = OpenFirstAvailablePrimary(O_RDWR | O_CLOEXEC))
     return std::move(Err);