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Fix building libc++ with the macOS 10.13 SDK with -mmacosx-version-min=10.12 or lower. 

The 10.13 SDK always defines utimensat() (with an availability(macosx=10.13) annotation)
and unconditionally defines UTIME_OMIT, so use the compile-time availability macros
on Apple platforms instead.

For people statically linking libc++, it might make sense to also provide an opt-in
option for using __builtin_available() to dynamically check for the OS version,
but for now let's do the smallest thing needed to unbreak the build.

Based on a patch by Eric Fiselier <eric@efcs.ca>: https://reviews.llvm.org/D34249
Fixes PR33469.

llvm-svn: 324385
This commit is contained in:
Nico Weber 2018-02-06 19:17:41 +00:00
parent a894201313
commit 6ef990e9ce
1 changed files with 29 additions and 4 deletions
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33
libcxx/src/experimental/filesystem/operations.cpp
View File

@ -21,7 +21,34 @@
#include <sys/stat.h>
#include <sys/statvfs.h>
#include <fcntl.h> /* values for fchmodat */
#if !defined(UTIME_OMIT)
#if (__APPLE__)
#if defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__)
#if __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ >= 101300
#define _LIBCXX_USE_UTIMENSAT
#endif
#elif defined(__ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__)
#if __ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__ >= 110000
#define _LIBCXX_USE_UTIMENSAT
#endif
#elif defined(__ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__)
#if __ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__ >= 110000
#define _LIBCXX_USE_UTIMENSAT
#endif
#elif defined(__ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__)
#if __ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__ >= 40000
#define _LIBCXX_USE_UTIMENSAT
#endif
#endif // __ENVIRONMENT_.*_VERSION_MIN_REQUIRED__
#else
// We can use the presence of UTIME_OMIT to detect platforms that provide
// utimensat.
#if defined(UTIME_OMIT)
#define _LIBCXX_USE_UTIMENSAT
#endif
#endif // __APPLE__
#if !defined(_LIBCXX_USE_UTIMENSAT)
#include <sys/time.h> // for ::utimes as used in __last_write_time
#endif
@ -560,9 +587,7 @@ void __last_write_time(const path& p, file_time_type new_time,
using namespace std::chrono;
std::error_code m_ec;
// We can use the presence of UTIME_OMIT to detect platforms that do not
// provide utimensat.
#if !defined(UTIME_OMIT)
#if !defined(_LIBCXX_USE_UTIMENSAT)
// This implementation has a race condition between determining the
// last access time and attempting to set it to the same value using
// ::utimes