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+# Supported API by libc
+
+These files are read by [`build.rs`](../build.rs) and turned into tests to
+ensure that APIs aren't removed between libc releases.
+
+## File order
+
+Files are including in the following order:
+ * Family, e.g. `unix.txt`. NOTE: Windows is skipped here and includes as OS
+   name below.
+ * Vendor, e.g. `apple.txt`. This allows us to have a single file with system
+   calls shared between multiple OSs, e.g. `ios.txt`, `macos.txt` share the same
+   kernel.
+ * OS, e.g `linux.txt`, `macos.txt`, `windows.txt`.
+ * Architecture specific system calls, e.g. `linux-x86_64.txt` or
+   `linux-aarch64.txt`.
+ * Target environment, e.g. `windows-mscv.txt` or `windows-gnu.txt`.