2 files changed, 40 insertions, 0 deletions
diff --git a/llvm/lib/Support/Unix/Program.inc b/llvm/lib/Support/Unix/Program.inc
index 117151c91d8..aa03d48438e 100644
--- a/llvm/lib/Support/Unix/Program.inc
+++ b/llvm/lib/Support/Unix/Program.inc
@@ -32,6 +32,9 @@
 #if HAVE_FCNTL_H
 #include <fcntl.h>
 #endif
+#if HAVE_UNISTD_H
+#include <unistd.h>
+#endif
 #ifdef HAVE_POSIX_SPAWN
 #include <spawn.h>
 #if !defined(__APPLE__)
@@ -409,4 +412,25 @@ error_code Program::ChangeStderrToBinary(){
   return make_error_code(errc::success);
 }
 
+bool llvm::sys::argumentsFitWithinSystemLimits(ArrayRef<const char*> Args) {
+  static long ArgMax = sysconf(_SC_ARG_MAX);
+
+  // System says no practical limit.
+  if (ArgMax == -1)
+    return true;
+
+  // Conservatively account for space required by environment variables.
+  ArgMax /= 2;
+
+  size_t ArgLength = 0;
+  for (ArrayRef<const char*>::iterator I = Args.begin(), E = Args.end();
+       I != E; ++I) {
+    ArgLength += strlen(*I) + 1;
+    if (ArgLength > size_t(ArgMax)) {
+      return false;
+    }
+  }
+  return true;
+}
+
 }
diff --git a/llvm/lib/Support/Windows/Program.inc b/llvm/lib/Support/Windows/Program.inc
index 691d6d45550..994a09764e3 100644
--- a/llvm/lib/Support/Windows/Program.inc
+++ b/llvm/lib/Support/Windows/Program.inc
@@ -396,4 +396,20 @@ error_code Program::ChangeStderrToBinary(){
   return make_error_code(errc::success);
 }
 
+bool llvm::sys::argumentsFitWithinSystemLimits(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;
+  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.
+    ArgLength += ArgLenWithQuotes(*I) + 1;
+    if (ArgLength > MaxCommandStringLength) {
+      return false;
+    }
+  }
+  return true;
+}
+
 }