1 files changed, 5 insertions, 0 deletions
diff --git a/llvm/autoconf/configure.ac b/llvm/autoconf/configure.ac
index e0bc78310c9..807de559036 100644
--- a/llvm/autoconf/configure.ac
+++ b/llvm/autoconf/configure.ac
@@ -73,6 +73,11 @@ if test ${srcdir} != "." ; then
   fi
 fi
 
+dnl Quit if it is an in-source build
+if test ${srcdir} == "." ; then
+  AC_MSG_ERROR([In-source builds are discouraged. Configure from a separate build directory.])
+fi
+
 dnl Default to empty (i.e. assigning the null string to) CFLAGS and CXXFLAGS,
 dnl instead of the autoconf default (for example, '-g -O2' for CC=gcc).
 : ${CFLAGS=}