Follow-up fixes to make it work with wasi-libc (swiftlang#1095)

* Gate `fchown` and `fchmod` calls behind `os(WASI)`

They are not available on WASI, so we gate them behind `os(WASI)`.

* Add missing constant shims for wasi-libc

* Use `futimens` instead of legacy `futimes`

wasi-libc does not provide `futimes` as it is a legacy function.
https://github.com/WebAssembly/wasi-libc/blob/574b88da481569b65a237cb80daf9a2d5aeaf82d/libc-top-half/musl/include/sys/time.h#L34

Author: kateinoigakukun

Sources/FoundationEssentials/FileManager/FileOperations.swift

@@ -940,26 +940,30 @@ enum _FileOperations {
         #endif
         var statInfo = stat()
         if fstat(srcFD, &statInfo) == 0 {
+            #if !os(WASI) // WASI doesn't have fchown for now
             // Copy owner/group
             if fchown(dstFD, statInfo.st_uid, statInfo.st_gid) != 0 {
                 try delegate.throwIfNecessary(errno, srcPath(), dstPath())
             }
+            #endif
 
             // Copy modification date
-            let value = timeval(tv_sec: statInfo.st_mtim.tv_sec, tv_usec: statInfo.st_mtim.tv_nsec / 1000)
+            let value = statInfo.st_mtim
             var tv = (value, value)
             try withUnsafePointer(to: &tv) {
-                try $0.withMemoryRebound(to: timeval.self, capacity: 2) {
-                    if futimes(dstFD, $0) != 0 {
+                try $0.withMemoryRebound(to: timespec.self, capacity: 2) {
+                    if futimens(dstFD, $0) != 0 {
                         try delegate.throwIfNecessary(errno, srcPath(), dstPath())
                     }
                 }
             }
 
+            #if !os(WASI) // WASI doesn't have fchmod for now
             // Copy permissions
             if fchmod(dstFD, statInfo.st_mode) != 0 {
                 try delegate.throwIfNecessary(errno, srcPath(), dstPath())
             }
+            #endif
         } else {
             try delegate.throwIfNecessary(errno, srcPath(), dstPath())
         }

Sources/FoundationEssentials/WASILibc+Extensions.swift

@@ -49,5 +49,14 @@ internal var O_TRUNC: Int32 {
 internal var O_WRONLY: Int32 {
     return _platform_shims_O_WRONLY()
 }
+internal var O_RDONLY: Int32 {
+    return _platform_shims_O_RDONLY()
+}
+internal var O_DIRECTORY: Int32 {
+    return _platform_shims_O_DIRECTORY()
+}
+internal var O_NOFOLLOW: Int32 {
+    return _platform_shims_O_NOFOLLOW()
+}
 
 #endif // os(WASI)

Sources/_FoundationCShims/include/platform_shims.h

@@ -102,6 +102,10 @@ static inline int32_t _platform_shims_O_CREAT(void) { return O_CREAT; }
 static inline int32_t _platform_shims_O_EXCL(void) { return O_EXCL; }
 static inline int32_t _platform_shims_O_TRUNC(void) { return O_TRUNC; }
 static inline int32_t _platform_shims_O_WRONLY(void) { return O_WRONLY; }
+static inline int32_t _platform_shims_O_RDONLY(void) { return O_RDONLY; }
+static inline int32_t _platform_shims_O_DIRECTORY(void) { return O_DIRECTORY; }
+static inline int32_t _platform_shims_O_NOFOLLOW(void) { return O_NOFOLLOW; }
+
 #endif
 
 #endif /* CSHIMS_PLATFORM_SHIMS */