Allocate and pass a resolved_path buffer to realpath as older macos versions

bin/file_macos.cc

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include <errno.h>
 #include <fcntl.h>
 #include <sys/stat.h>
 #include <unistd.h>
 #include <libgen.h>
+#include <limits.h>
 
 #include "bin/builtin.h"
 #include "bin/file.h"
 
 class FileHandle {
  public:
   explicit FileHandle(int fd) : fd_(fd) { }
   ~FileHandle() { }
   int fd() const { return fd_; }
   void set_fd(int fd) { fd_ = fd; }
@@ skipping 95 matching lines @@
 
 
 bool File::IsAbsolutePath(const char* pathname) {
   return (pathname != NULL && pathname[0] == '/');
 }
 
 
 char* File::GetCanonicalPath(const char* pathname) {
   char* abs_path = NULL;
   if (pathname != NULL) {
-    abs_path = realpath(pathname, NULL);
+    // On some older MacOs versions the default behaviour of realpath allocating
+    // space for the resolved_path when a NULL is passed in does not seem to
+    // work, so we explicitly allocate space. The caller is responsible for
+    // freeing this space as in a regular realpath call.
+    char* resolved_path = reinterpret_cast<char*>(malloc(PATH_MAX+1));
+    ASSERT(resolved_path != NULL);
+    abs_path = realpath(pathname, resolved_path);
     assert(abs_path == NULL || IsAbsolutePath(abs_path));
   }
   return abs_path;
 }
 
 
 const char* File::PathSeparator() {
   return "/";
 }
 
 
 const char* File::StringEscapedPathSeparator() {
   return "/";
 }