Add doc to OS::StrNCpy

src/platform.h

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
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@@ skipping 222 matching lines @@
   };
 
   // Safe formatting print. Ensures that str is always null-terminated.
   // Returns the number of chars written, or -1 if output was truncated.
   static int SNPrintF(Vector<char> str, const char* format, ...);
   static int VSNPrintF(Vector<char> str,
                        const char* format,
                        va_list args);
 
   static char* StrChr(char* str, int c);
+
+  // Calls strncpy in POSIX and strncpy_s in Windows. It means that

[Mads Ager (chromium), 2010/01/19 16:07:06]

I think it would make more sense to change the implementation of StrNCpy to work
the same on all platforms.  Why don't we change StrNCpy to always null terminate
and document this consistent behavior instead?

[Søren Thygesen Gjesse, 2010/01/19 16:13:06]

Then we should probably stick to the strncpy_s semantics where the dest[0] is
set to '\0' if dest does not have room for the n characters.

+  // depending on platform it may or may not set terminating 0 and
+  // it may or may not check length of dest buffer (dest must fit
+  // n bytes plus 1 terminating byte).
   static void StrNCpy(Vector<char> dest, const char* src, size_t n);
 
   // Support for profiler.  Can do nothing, in which case ticks
   // occuring in shared libraries will not be properly accounted
   // for.
   static void LogSharedLibraryAddresses();
 
   // The return value indicates the CPU features we are sure of because of the
   // OS.  For example MacOSX doesn't run on any x86 CPUs that don't have SSE2
   // instructions.
@@ skipping 294 matching lines @@
   bool active_;
   PlatformData* data_;  // Platform specific data.
   DISALLOW_IMPLICIT_CONSTRUCTORS(Sampler);
 };
 
 #endif  // ENABLE_LOGGING_AND_PROFILING
 
 } }  // namespace v8::internal
 
 #endif  // V8_PLATFORM_H_