libunwind: prefer __has_feature(capabilities) to defined(__CHERI__)

Author: brooksdavis

libunwind/src/AddressSpace.hpp

@@ -174,7 +174,7 @@ class _LIBUNWIND_HIDDEN LocalAddressSpace {
 public:
   typedef uintptr_t pint_t;
   typedef intptr_t  sint_t;
-#ifndef __CHERI__
+#if !__has_feature(capabilities)
   typedef libunwind::fake_capability_t capability_t;
 #else
   typedef ::uintcap_t capability_t;
@@ -342,7 +342,7 @@ class _LIBUNWIND_HIDDEN LocalAddressSpace {
   static pint_t to_pint_t(capability_t cap) {
 #ifdef __CHERI_PURE_CAPABILITY__
     return (uintcap_t)cap;
-#elif defined(__CHERI__)
+#elif __has_feature(capabilities)
     return (__cheri_addr pint_t)cap;
 #else
     pint_t result;
@@ -351,7 +351,7 @@ class _LIBUNWIND_HIDDEN LocalAddressSpace {
 #endif
   }
   static capability_t to_capability_t(pint_t pint) {
-#ifdef __CHERI__
+#if __has_feature(capabilities)
     return (uintcap_t)pint;
 #else
     capability_t result;

libunwind/src/DwarfInstructions.hpp

@@ -495,7 +495,7 @@ DwarfInstructions<A, R>::evaluateExpression(pint_t expression, A &addressSpace,
 // XXXAR: I am not entirely sure these operations should work on a uintcap_t
 // but if it's an untagged integer value it is fine
 #pragma clang diagnostic push
-#ifdef __CHERI__
+#if __has_feature(capabilities)
 #pragma clang diagnostic ignored "-Wcheri-bitwise-operations"
 #endif
   const bool log = true;

libunwind/src/Registers.hpp

@@ -24,7 +24,7 @@ namespace libunwind {
 // For emulating 128-bit registers
 struct v128 { uint32_t vec[4]; };
 // For emulating CHERI capability
-#ifndef __CHERI__
+#if !_has_feature(capabilities)
 struct __attribute__((aligned(16))) fake_capability {
   char bytes[16];
 };
@@ -3308,7 +3308,7 @@ class _LIBUNWIND_HIDDEN Registers_mips_newabi {
   Registers_mips_newabi();
   Registers_mips_newabi(const void *registers);
   CAPABILITIES_NOT_SUPPORTED
-#ifdef __CHERI__
+#if __has_feature(capabilities)
 #pragma message("Should also handle capability registers here.")
 #endif