8242485: Null _file checking in fileStream::flush()

Reviewed-by: dholmes, ysuenaga, iklam

Author: Denghui Dong

src/hotspot/share/utilities/ostream.cpp

@@ -533,8 +533,8 @@ void fileStream::write(const char* s, size_t len) {
   if (_file != NULL)  {
     // Make an unused local variable to avoid warning from gcc compiler.
     size_t count = fwrite(s, 1, len, _file);
+    update_position(s, len);
   }
-  update_position(s, len);
 }
 
 long fileStream::fileSize() {
@@ -551,9 +551,12 @@ long fileStream::fileSize() {
 }
 
 char* fileStream::readln(char *data, int count ) {
-  char * ret = ::fgets(data, count, _file);
-  //Get rid of annoying \n char
-  data[::strlen(data)-1] = '\0';
+  char * ret = NULL;
+  if (_file != NULL) {
+    ret = ::fgets(data, count, _file);
+    //Get rid of annoying \n char
+    data[::strlen(data)-1] = '\0';
+  }
   return ret;
 }
 
@@ -565,15 +568,17 @@ fileStream::~fileStream() {
 }
 
 void fileStream::flush() {
-  fflush(_file);
+  if (_file != NULL) {
+    fflush(_file);
+  }
 }
 
 void fdStream::write(const char* s, size_t len) {
   if (_fd != -1) {
     // Make an unused local variable to avoid warning from gcc compiler.
     size_t count = ::write(_fd, s, (int)len);
+    update_position(s, len);
   }
-  update_position(s, len);
 }
 
 defaultStream* defaultStream::instance = NULL;

src/hotspot/share/utilities/ostream.hpp

@@ -230,11 +230,11 @@ class fileStream : public outputStream {
   ~fileStream();
   bool is_open() const { return _file != NULL; }
   virtual void write(const char* c, size_t len);
-  size_t read(void *data, size_t size, size_t count) { return ::fread(data, size, count, _file); }
+  size_t read(void *data, size_t size, size_t count) { return _file != NULL ? ::fread(data, size, count, _file) : 0; }
   char* readln(char *data, int count);
-  int eof() { return feof(_file); }
+  int eof() { return _file != NULL ? feof(_file) : -1; }
   long fileSize();
-  void rewind() { ::rewind(_file); }
+  void rewind() { if (_file != NULL) ::rewind(_file); }
   void flush();
 };