Remove need for PTRDIFF_MAX

It's just as easy to calculate the maximum value directly.

src/reader.c

@@ -460,5 +460,5 @@
 
     }
 
-    if (parser->offset >= PTRDIFF_MAX)
+    if (parser->offset >= MAX_FILE_SIZE) {
         return yaml_parser_set_reader_error(parser, "input is too long",
@@ -464,5 +464,6 @@
         return yaml_parser_set_reader_error(parser, "input is too long",
-                PTRDIFF_MAX, -1);
+            parser->offset, -1);
+    }
 
     return 1;
 }
@@ -466,4 +467,3 @@
 
     return 1;
 }
-

src/yaml_private.h

@@ -8,28 +8,6 @@
 #include <limits.h>
 #include <stddef.h>
 
-#ifndef _MSC_VER
-#if defined(__sun) || defined(__sun__)
-#include <sys/inttypes.h>
-#define PTRDIFF_MAX INT_MAX
-#else
-#include <stdint.h>
-#ifndef PTRDIFF_MAX /* gcc on HP-UX */
-#ifdef _LP64
-#define PTRDIFF_MAX 0x7FFFFFFFFFFFFFFFLL
-#else
-#define PTRDIFF_MAX 0x7FFFFFFFL
-#endif
-#endif
-#endif
-#else
-#ifdef _WIN64
-#define PTRDIFF_MAX _I64_MAX
-#else
-#define PTRDIFF_MAX INT_MAX
-#endif
-#endif
-
 /*
  * Memory management.
  */
@@ -89,6 +67,17 @@
 #define OUTPUT_RAW_BUFFER_SIZE  (OUTPUT_BUFFER_SIZE*2+2)
 
 /*
+ * The maximum size of a YAML input file.
+ * This used to be PTRDIFF_MAX, but that's not entirely portable
+ * because stdint.h isn't available on all platforms.
+ * It is not entirely clear why this isn't the maximum value
+ * that can fit into the parser->offset field.
+ */
+
+#define MAX_FILE_SIZE (~(size_t)0 / 2)
+
+
+/*
  * The size of other stacks and queues.
  */