unwind: use a more portable endianness check in EHABI
The ARM specific code was trying to determine endianness using the
`__LITTLE_ENDIAN__` macro which is not guaranteed to be defined.
When not defined, it makes libunwind to build the big-endian code even
when the compiler builds for a little-endian target.
This change allows building libunwind with the `musl-gcc` toolchain
which does not define `__LITTLE_ENDIAN__`. Use `__BYTE_ORDER__`
instead.
Patch by Idan Freiberg!
GitOrigin-RevId: 68c50708d1f2b9aee3f10ec710df0b1387f701e5
diff --git a/src/Unwind-EHABI.cpp b/src/Unwind-EHABI.cpp
index a8a64cb..32b5cbc 100644
--- a/src/Unwind-EHABI.cpp
+++ b/src/Unwind-EHABI.cpp
@@ -31,10 +31,12 @@
// signinficant byte.
uint8_t getByte(const uint32_t* data, size_t offset) {
const uint8_t* byteData = reinterpret_cast<const uint8_t*>(data);
-#ifdef __LITTLE_ENDIAN__
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
return byteData[(offset & ~(size_t)0x03) + (3 - (offset & (size_t)0x03))];
-#else
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
return byteData[offset];
+#else
+#error "Unable to determine endianess"
#endif
}
@@ -943,10 +945,12 @@
// SP is only 32-bit aligned so don't copy 64-bit at a time.
uint64_t w0 = *sp++;
uint64_t w1 = *sp++;
-#ifdef __LITTLE_ENDIAN__
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
uint64_t value = (w1 << 32) | w0;
-#else
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
uint64_t value = (w0 << 32) | w1;
+#else
+#error "Unable to determine endianess"
#endif
if (_Unwind_VRS_Set(context, regclass, i, representation, &value) !=
_UVRSR_OK)
