Index: include/llvm/Support/Program.h
===================================================================
--- include/llvm/Support/Program.h
+++ include/llvm/Support/Program.h
@@ -130,7 +130,7 @@
 
   /// Return true if the given arguments fit within system-specific
   /// argument length limits.
-  bool argumentsFitWithinSystemLimits(ArrayRef<const char*> Args);
+  bool commandLineFitsWithinSystemLimits(StringRef Program, ArrayRef<const char*> Args);
 
   /// File encoding options when writing contents that a non-UTF8 tool will
   /// read (on Windows systems). For UNIX, we always use UTF-8.
Index: lib/Support/Unix/Program.inc
===================================================================
--- lib/Support/Unix/Program.inc
+++ lib/Support/Unix/Program.inc
@@ -446,7 +446,7 @@
   return EC;
 }
 
-bool llvm::sys::argumentsFitWithinSystemLimits(ArrayRef<const char*> Args) {
+bool llvm::sys::commandLineFitsWithinSystemLimits(StringRef Program, ArrayRef<const char*> Args) {
   static long ArgMax = sysconf(_SC_ARG_MAX);
 
   // System says no practical limit.
@@ -456,7 +456,7 @@
   // Conservatively account for space required by environment variables.
   long HalfArgMax = ArgMax / 2;
 
-  size_t ArgLength = 0;
+  size_t ArgLength = Program.size() + 1;
   for (ArrayRef<const char*>::iterator I = Args.begin(), E = Args.end();
        I != E; ++I) {
     ArgLength += strlen(*I) + 1;
Index: lib/Support/Windows/Program.inc
===================================================================
--- lib/Support/Windows/Program.inc
+++ lib/Support/Windows/Program.inc
@@ -535,14 +535,15 @@
   return EC;
 }
 
-bool llvm::sys::argumentsFitWithinSystemLimits(ArrayRef<const char*> Args) {
+bool llvm::sys::commandLineFitsWithinSystemLimits(StringRef Program, ArrayRef<const char*> Args) {
   // The documented max length of the command line passed to CreateProcess.
   static const size_t MaxCommandStringLength = 32768;
-  size_t ArgLength = 0;
+  // Account for the trailing space for the program path and the
+  // trailing NULL of the last argument.
+  size_t ArgLength = ArgLenWithQuotes(Program.str().c_str()) + 2;
   for (ArrayRef<const char*>::iterator I = Args.begin(), E = Args.end();
        I != E; ++I) {
-    // Account for the trailing space for every arg but the last one and the
-    // trailing NULL of the last argument.
+    // Account for the trailing space for every arg
     ArgLength += ArgLenWithQuotes(*I) + 1;
     if (ArgLength > MaxCommandStringLength) {
       return false;