Greatly simplify dlpath() implementation on OSX

src/sys.c

@@ -561,66 +561,6 @@ DLLEXPORT size_t jl_get_alignment(jl_datatype_t *ty)
     return ty->alignment;
 }
 
-
-// Dynamic Library interrogation
-
-#ifdef __APPLE__
-// This code gratefully lifted from: http://stackoverflow.com/questions/20481058
-#ifdef __LP64__
-typedef struct mach_header_64 mach_header_t;
-typedef struct segment_command_64 segment_command_t;
-typedef struct nlist_64 nlist_t;
-#else
-typedef struct mach_header mach_header_t;
-typedef struct segment_command segment_command_t;
-typedef struct nlist nlist_t;
-#endif
-
-static const char *first_external_symbol_for_image(const mach_header_t *header)
-{
-    Dl_info info;
-    if (dladdr(header, &info) == 0)
-        return NULL;
-
-    segment_command_t *seg_linkedit = NULL;
-    segment_command_t *seg_text = NULL;
-    struct symtab_command *symtab = NULL;
-
-    struct load_command *cmd = (struct load_command *)((intptr_t)header + sizeof(mach_header_t));
-    for (uint32_t i = 0; i < header->ncmds; i++, cmd = (struct load_command *)((intptr_t)cmd + cmd->cmdsize)) {
-        switch(cmd->cmd) {
-        case LC_SEGMENT:
-        case LC_SEGMENT_64:
-            if (!strcmp(((segment_command_t *)cmd)->segname, SEG_TEXT))
-                seg_text = (segment_command_t *)cmd;
-            else if (!strcmp(((segment_command_t *)cmd)->segname, SEG_LINKEDIT))
-                seg_linkedit = (segment_command_t *)cmd;
-            break;
-
-        case LC_SYMTAB:
-            symtab = (struct symtab_command *)cmd;
-            break;
-        }
-    }
-
-    if ((seg_text == NULL) || (seg_linkedit == NULL) || (symtab == NULL))
-        return NULL;
-
-    intptr_t file_slide = ((intptr_t)seg_linkedit->vmaddr - (intptr_t)seg_text->vmaddr) - seg_linkedit->fileoff;
-    intptr_t strings = (intptr_t)header + (symtab->stroff + file_slide);
-    nlist_t *sym = (nlist_t *)((intptr_t)header + (symtab->symoff + file_slide));
-
-    for (uint32_t i = 0; i < symtab->nsyms; i++, sym++) {
-        if ((sym->n_type & N_EXT) != N_EXT || !sym->n_value)
-            continue;
-
-        return (const char*)strings + sym->n_un.n_strx;
-    }
-
-    return NULL;
-}
-#endif
-
 // Takes a handle (as returned from dlopen()) and returns the absolute path to the image loaded
 DLLEXPORT const char *jl_pathname_for_handle(uv_lib_t *uv_lib)
 {
@@ -629,16 +569,17 @@ DLLEXPORT const char *jl_pathname_for_handle(uv_lib_t *uv_lib)
 
     void *handle = uv_lib->handle;
 #ifdef __APPLE__
+    // Iterate through all images currently in memory
     for (int32_t i = _dyld_image_count(); i >= 0 ; i--) {
-        const char *first_symbol = first_external_symbol_for_image((const mach_header_t *)_dyld_get_image_header(i));
-        if (first_symbol && strlen(first_symbol) > 1) {
-            handle = (void*)((intptr_t)handle | 1); // in order to trigger findExportedSymbol instead of findExportedSymbolInImageOrDependentImages. See `dlsym` implementation at http://opensource.apple.com/source/dyld/dyld-239.3/src/dyldAPIs.cpp
-            first_symbol++; // in order to remove the leading underscore
-            void *address = dlsym(handle, first_symbol);
-            Dl_info info;
-            if (dladdr(address, &info))
-                return info.dli_fname;
-        }
+        // dlopen() each image, check handle
+        const char *image_name = _dyld_get_image_name(i);
+        uv_lib_t *probe_lib = jl_load_dynamic_library(image_name, JL_RTLD_DEFAULT);
+        void *probe_handle = probe_lib->handle;
+        uv_dlclose(probe_lib);
+
+        // If the handle is the same as what was passed in, return this image name
+        if (handle == probe_handle)
+            return image_name;
     }
 
 #elif defined(_OS_WINDOWS_)