8285506: Unify os::vsnprintf implementations

Reviewed-by: jwaters, kbarrett, jsjolen

Author: David Holmes

src/hotspot/os/posix/os_posix.cpp

@@ -425,17 +425,6 @@ char* os::map_memory_to_file_aligned(size_t size, size_t alignment, int file_des
   return aligned_base;
 }
 
-int os::vsnprintf(char* buf, size_t len, const char* fmt, va_list args) {
-  // All supported POSIX platforms provide C99 semantics.
-  ALLOW_C_FUNCTION(::vsnprintf, int result = ::vsnprintf(buf, len, fmt, args);)
-  // If an encoding error occurred (result < 0) then it's not clear
-  // whether the buffer is NUL terminated, so ensure it is.
-  if ((result < 0) && (len > 0)) {
-    buf[len - 1] = '\0';
-  }
-  return result;
-}
-
 int os::get_fileno(FILE* fp) {
   return NOT_AIX(::)fileno(fp);
 }

src/hotspot/os/windows/os_windows.cpp

@@ -1739,17 +1739,6 @@ void os::get_summary_os_info(char* buf, size_t buflen) {
   if (nl != nullptr) *nl = '\0';
 }
 
-int os::vsnprintf(char* buf, size_t len, const char* fmt, va_list args) {
-  // Starting with Visual Studio 2015, vsnprint is C99 compliant.
-  ALLOW_C_FUNCTION(::vsnprintf, int result = ::vsnprintf(buf, len, fmt, args);)
-  // If an encoding error occurred (result < 0) then it's not clear
-  // whether the buffer is NUL terminated, so ensure it is.
-  if ((result < 0) && (len > 0)) {
-    buf[len - 1] = '\0';
-  }
-  return result;
-}
-
 static inline time_t get_mtime(const char* filename) {
   struct stat st;
   int ret = os::stat(filename, &st);

src/hotspot/share/runtime/os.cpp

@@ -111,6 +111,16 @@ int os::snprintf_checked(char* buf, size_t len, const char* fmt, ...) {
   return result;
 }
 
+int os::vsnprintf(char* buf, size_t len, const char* fmt, va_list args) {
+  ALLOW_C_FUNCTION(::vsnprintf, int result = ::vsnprintf(buf, len, fmt, args);)
+  // If an encoding error occurred (result < 0) then it's not clear
+  // whether the buffer is NUL terminated, so ensure it is.
+  if ((result < 0) && (len > 0)) {
+    buf[len - 1] = '\0';
+  }
+  return result;
+}
+
 // Fill in buffer with current local time as an ISO-8601 string.
 // E.g., YYYY-MM-DDThh:mm:ss.mmm+zzzz.
 // Returns buffer, or null if it failed.

src/hotspot/share/runtime/os.hpp

@@ -771,8 +771,8 @@ class os: AllStatic {
   static void *find_agent_function(JvmtiAgent *agent_lib, bool check_lib,
                                    const char *syms[], size_t syms_len);
 
-  // Provide C99 compliant versions of these functions, since some versions
-  // of some platforms don't.
+  // Provide wrapper versions of these functions to guarantee NUL-termination
+  // in all cases.
   static int vsnprintf(char* buf, size_t len, const char* fmt, va_list args) ATTRIBUTE_PRINTF(3, 0);
   static int snprintf(char* buf, size_t len, const char* fmt, ...) ATTRIBUTE_PRINTF(3, 4);