[libc] Change fcntl cmd when only fcntl64 is available

[mikhailramalho]

In some systems like rv32, only fcntl64 is available and it employs a different structure for file locking and the correspoding F_GETLK64, F_SETLK64, and F_SETLKW64 commands.

So if we use fcntl64, the F_GETLK, F_SETLK, and F_SETLKW commands need to be changed to their 64 versions. This patch adds new cases to the swich(cmd) in our implementation of fcntl to do that.

The default case was moved to outside the switch, so we don't need to change anything, the F_GETLK, F_SETLK, and F_SETLKW commands will just go through the old implementation.

[llvmbot]

@llvm/pr-subscribers-libc

Author: Mikhail R. Gadelha (mikhailramalho)

Changes

In some systems like rv32, only fcntl64 is available and it employs a different structure for file locking and the correspoding F_GETLK64, F_SETLK64, and F_SETLKW64 commands.

So if we use fcntl64, the F_GETLK, F_SETLK, and F_SETLKW commands need to be changed to their 64 versions. This patch adds new cases to the swich(cmd) in our implementation of fcntl to do that.

The default case was moved to outside the switch, so we don't need to change anything, the F_GETLK, F_SETLK, and F_SETLKW commands will just go through the old implementation.

---

Full diff: https://github.com/llvm/llvm-project/pull/99675.diff

1 Files Affected:

• (modified) libc/src/__support/OSUtil/linux/fcntl.cpp (+28-8)

diff --git a/libc/src/__support/OSUtil/linux/fcntl.cpp b/libc/src/__support/OSUtil/linux/fcntl.cpp
index e11013121b04b..44f10b6c59766 100644
--- a/libc/src/__support/OSUtil/linux/fcntl.cpp
+++ b/libc/src/__support/OSUtil/linux/fcntl.cpp
@@ -86,17 +86,37 @@ int fcntl(int fd, int cmd, void *arg) {
     libc_errno = -ret;
     return -1;
   }
+  case F_GETLK: {
+#if defined(SYS_fcntl64)
+    if constexpr (FCNTL_SYSCALL_ID == SYS_fcntl64)
+      return fcntl(fd, F_GETLK64, arg);
+#endif
+    break;
+  }
+  case F_SETLK: {
+#if defined(SYS_fcntl64)
+    if constexpr (FCNTL_SYSCALL_ID == SYS_fcntl64)
+      return fcntl(fd, F_SETLK64, arg);
+#endif
+    break;
+  }
+  case F_SETLKW: {
+#if defined(SYS_fcntl64)
+    if constexpr (FCNTL_SYSCALL_ID == SYS_fcntl64)
+      return fcntl(fd, F_SETLKW64, arg);
+#endif
+    break;
+  }
   // The general case
-  default: {
-    int retVal = LIBC_NAMESPACE::syscall_impl<int>(
-        FCNTL_SYSCALL_ID, fd, cmd, reinterpret_cast<void *>(arg));
-    if (retVal >= 0) {
-      return retVal;
-    }
-    libc_errno = -retVal;
-    return -1;
+  default:;
   }
+  int retVal = LIBC_NAMESPACE::syscall_impl<int>(FCNTL_SYSCALL_ID, fd, cmd,
+                                                 reinterpret_cast<void *>(arg));
+  if (retVal >= 0) {
+    return retVal;
   }
+  libc_errno = -retVal;
+  return -1;
 }
 
 } // namespace internal

[mikhailramalho]

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