[PATCH] Cygwin: Update _endian.h to handle unsupported arch

[Thirumalai Nagalingam]

Hi,

This patch Update _endian.h so that it explicitly throws an error when encountering
an unsupported architecture instead of returning the unmodified x.
Also tighten the arch detection logic by adding an explicit LE check.

Thanks & regards
Thirumalai Nagalingam

In-lined patch:

diff --git a/winsup/cygwin/include/machine/_endian.h b/winsup/cygwin/include/machine/_endian.h
index 681ae4abe..e591f375d 100644
--- a/winsup/cygwin/include/machine/_endian.h
+++ b/winsup/cygwin/include/machine/_endian.h
@@ -28,8 +28,10 @@ __ntohl(__uint32_t _x)
 {
 #if defined(__x86_64__)
        __asm__("bswap %0" : "=r" (_x) : "0" (_x));
-#elif defined(__aarch64__)
+#elif defined(__aarch64__) && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
     __asm__("rev %w0, %w0" : "=r" (_x) : "0" (_x));
+#else
+#error "unsupported architecture"
 #endif
        return _x;
 }
@@ -41,10 +43,12 @@ __ntohs(__uint16_t _x)
        __asm__("xchgb %b0,%h0"         /* swap bytes           */
                : "=Q" (_x)
                :  "0" (_x));
-#elif defined(__aarch64__)
+#elif defined(__aarch64__) && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
     __asm__("\n\
                        rev16 %0, %0 \n\
                " : "=r" (_x) : "0" (_x));
+#else
+#error "unsupported architecture"
 #endif
        return _x;
 }
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