[Runtime] Avoid referring to enum _dyld_section_location_kind.

If the SDK has dyld_priv.h but doesn't have enum _dyld_section_location_kind, we can't use enum _dyld_section_location_kind and it's hard to detect that. Instead, just use `int`, and use #defines for the values.

Author: mikeash

stdlib/public/runtime/ImageInspectionMachO.cpp

@@ -33,22 +33,17 @@
 #if __has_include(<objc/objc-internal.h>) && __has_include(<mach-o/dyld_priv.h>)
 #include <mach-o/dyld_priv.h>
 #include <objc/objc-internal.h>
-#else
-
-// Bring our own definition of enum _dyld_section_location_kind and some of its
-// values. They'll be unused when we can't include dyld_priv.h, but the code
-// needs them in order to compile.
-enum _dyld_section_location_kind {
-  _dyld_section_location_text_swift5_protos,
-  _dyld_section_location_text_swift5_proto,
-  _dyld_section_location_text_swift5_types,
-  _dyld_section_location_text_swift5_replace,
-  _dyld_section_location_text_swift5_replace2,
-  _dyld_section_location_text_swift5_ac_funcs,
-};
-
 #endif
 
+// Bring our own definition of _dyld_section_location constants in case we're
+// using an older SDK that doesn't have them.
+#define _dyld_section_location_text_swift5_protos   0
+#define _dyld_section_location_text_swift5_proto    1
+#define _dyld_section_location_text_swift5_types    2
+#define _dyld_section_location_text_swift5_replace  3
+#define _dyld_section_location_text_swift5_replace2 4
+#define _dyld_section_location_text_swift5_ac_funcs 5
+
 #if !OBJC_ADDLOADIMAGEFUNC2_DEFINED
 // If we don't have objc_addLoadImageFunc2, fall back to objc_addLoadImageFunc.
 // Use a #define so we don't have to conditionalize the calling code below.
@@ -80,7 +75,7 @@ using mach_header_platform = mach_header;
 
 // Callback for objc_addLoadImageFunc that just takes a mach_header.
 template <const char *SEGMENT_NAME, const char *SECTION_NAME,
-          enum _dyld_section_location_kind SECTION_KIND,
+          int SECTION_KIND,
           void CONSUME_BLOCK(const void *baseAddress, const void *start,
                              uintptr_t size)>
 void addImageCallback(const mach_header *mh) {
@@ -103,7 +98,7 @@ void addImageCallback(const mach_header *mh) {
 // Callback for objc_addLoadImageFunc2 that takes a mach_header and dyld info.
 #if OBJC_ADDLOADIMAGEFUNC2_DEFINED
 template <const char *SEGMENT_NAME, const char *SECTION_NAME,
-          enum _dyld_section_location_kind SECTION_KIND,
+          int SECTION_KIND,
           void CONSUME_BLOCK(const void *baseAddress, const void *start,
                              uintptr_t size)>
 void addImageCallback(const mach_header *mh,
@@ -121,7 +116,7 @@ void addImageCallback(const mach_header *mh,
 // Callback for _dyld_register_func_for_add_image that takes a mach_header and a
 // slide.
 template <const char *SEGMENT_NAME, const char *SECTION_NAME,
-          enum _dyld_section_location_kind SECTION_KIND,
+          int SECTION_KIND,
           void CONSUME_BLOCK(const void *baseAddress, const void *start,
                              uintptr_t size)>
 void addImageCallback(const mach_header *mh, intptr_t vmaddr_slide) {
@@ -132,8 +127,8 @@ void addImageCallback(const mach_header *mh, intptr_t vmaddr_slide) {
 
 template <const char *SEGMENT_NAME, const char *SECTION_NAME,
           const char *SEGMENT_NAME2, const char *SECTION_NAME2,
-          enum _dyld_section_location_kind SECTION_KIND,
-          enum _dyld_section_location_kind SECTION_KIND2,
+          int SECTION_KIND,
+          int SECTION_KIND2,
           void CONSUME_BLOCK(const void *baseAddress,
                              const void *start, uintptr_t size,
                              const void *start2, uintptr_t size2)>
@@ -168,8 +163,8 @@ void addImageCallback2Sections(const mach_header *mh) {
 #if OBJC_ADDLOADIMAGEFUNC2_DEFINED
 template <const char *SEGMENT_NAME, const char *SECTION_NAME,
           const char *SEGMENT_NAME2, const char *SECTION_NAME2,
-          enum _dyld_section_location_kind SECTION_KIND,
-          enum _dyld_section_location_kind SECTION_KIND2,
+          int SECTION_KIND,
+          int SECTION_KIND2,
           void CONSUME_BLOCK(const void *baseAddress,
                              const void *start, uintptr_t size,
                              const void *start2, uintptr_t size2)>
@@ -198,8 +193,8 @@ void addImageCallback2Sections(const mach_header *mh,
 // slide.
 template <const char *SEGMENT_NAME, const char *SECTION_NAME,
           const char *SEGMENT_NAME2, const char *SECTION_NAME2,
-          enum _dyld_section_location_kind SECTION_KIND,
-          enum _dyld_section_location_kind SECTION_KIND2,
+          int SECTION_KIND,
+          int SECTION_KIND2,
           void CONSUME_BLOCK(const void *baseAddress, const void *start,
                              uintptr_t size, const void *start2,
                              uintptr_t size2)>