From a1d0f15abbfdf3fc34bdfcfa6eb771f9ddef55a3 Mon Sep 17 00:00:00 2001
From: Eric Niebler <eniebler@fb.com>
Date: Thu, 2 Nov 2017 16:58:07 -0700
Subject: [PATCH] don't try to run the poly tests on gcc-4.9. they will fail.

Summary: gcc-4.9 does not support features that Poly needs. Disable the tests on that platform.

Reviewed By: meyering

Differential Revision: D6211674

fbshipit-source-id: 289f029122a45b0f9ec740c62b1faaafb51dcab5
---
 folly/Makefile.am       |  6 +++++-
 folly/Poly.cpp          |  6 ++++++
 folly/Poly.h            |  4 ++++
 folly/configure.ac      | 16 ++++++++++++++++
 folly/test/Makefile.am  |  2 ++
 folly/test/PolyTest.cpp |  4 ++++
 6 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/folly/Makefile.am b/folly/Makefile.am
index c24cd2c0..79bcecb0 100644
--- a/folly/Makefile.am
+++ b/folly/Makefile.am
@@ -571,7 +571,6 @@ libfolly_la_SOURCES = \
 	detail/SocketFastOpen.cpp \
 	MacAddress.cpp \
 	memory/ThreadCachedArena.cpp \
-	Poly.cpp \
 	portability/Dirent.cpp \
 	portability/Fcntl.cpp \
 	portability/Libgen.cpp \
@@ -713,6 +712,11 @@ libfolly_la_SOURCES += \
 	experimental/symbolizer/Symbolizer.cpp
 endif
 
+if HAVE_VARIABLE_TEMPLATES
+libfolly_la_SOURCES += \
+	Poly.cpp
+endif
+
 libfollybasesse42_la_LDFLAGS = $(AM_LDFLAGS) -version-info $(LT_VERSION)
 libfollybasesse42_la_CXXFLAGS = -msse4.2 -mpclmul
 
diff --git a/folly/Poly.cpp b/folly/Poly.cpp
index 352b1a0f..93829baf 100644
--- a/folly/Poly.cpp
+++ b/folly/Poly.cpp
@@ -14,6 +14,10 @@
  * limitations under the License.
  */
 
+#if defined(__GNUC__) && !defined(__clang__) && __GNUC__ < 5
+#pragma message "Folly.Poly requires gcc-5 or greater"
+#else
+
 #include <folly/Poly.h>
 
 namespace folly {
@@ -22,3 +26,5 @@ namespace detail {
 [[noreturn]] void throwBadPolyCast() { throw BadPolyCast(); }
 } // namespace detail
 } // namespace folly
+
+#endif
diff --git a/folly/Poly.h b/folly/Poly.h
index 218fbd89..6acac682 100644
--- a/folly/Poly.h
+++ b/folly/Poly.h
@@ -25,6 +25,10 @@
 
 #pragma once
 
+#if defined(__GNUC__) && !defined(__clang__) && __GNUC__ < 5
+#error Folly.Poly requires gcc-5 or greater
+#endif
+
 #include <cassert>
 #include <new>
 #include <type_traits>
diff --git a/folly/configure.ac b/folly/configure.ac
index 181f4687..826972e2 100644
--- a/folly/configure.ac
+++ b/folly/configure.ac
@@ -525,6 +525,22 @@ AC_DEFINE_UNQUOTED(
   [Define to 1 if the compiler has VLA (variable-length array) support,
    otherwise define to 0])
 
+AC_CACHE_CHECK(
+  [for variable template support],
+  [folly_cv_prog_cc_have_variable_templates],
+  [AC_COMPILE_IFELSE(
+    [AC_LANG_SOURCE[
+      template <class> constexpr bool g = true;
+      int main() {}
+    ]],
+    [folly_cv_prog_cc_have_variable_templates=yes],
+    [folly_cv_prog_cc_have_variable_templates=no])])
+
+AM_CONDITIONAL(
+  [HAVE_VARIABLE_TEMPLATES],
+  [test "x${folly_cv_prog_cc_have_variable_templates}" = "xyes"],
+  [Define to 1 if the compiler supports variable templates])
+
 # Checks for library functions.
 AC_CHECK_FUNCS([malloc_size \
                 malloc_usable_size \
diff --git a/folly/test/Makefile.am b/folly/test/Makefile.am
index dc49c5f8..e5da5010 100644
--- a/folly/test/Makefile.am
+++ b/folly/test/Makefile.am
@@ -223,9 +223,11 @@ fingerprint_test_SOURCES = FingerprintTest.cpp
 fingerprint_test_LDADD = libfollytestmain.la $(top_builddir)/libfollybenchmark.la
 TESTS += fingerprint_test
 
+if HAVE_VARIABLE_TEMPLATES
 poly_test_SOURCES = PolyTest.cpp
 poly_test_LDADD = libfollytestmain.la
 TESTS += poly_test
+endif
 
 portability_test_SOURCES = PortabilityTest.cpp
 portability_test_LDADD = libfollytestmain.la
diff --git a/folly/test/PolyTest.cpp b/folly/test/PolyTest.cpp
index bbd13b8f..7083a464 100644
--- a/folly/test/PolyTest.cpp
+++ b/folly/test/PolyTest.cpp
@@ -14,6 +14,9 @@
  * limitations under the License.
  */
 
+#if defined(__GNUC__) && !defined(__clang__) && __GNUC__ < 5
+#pragma message "Folly.Poly requires gcc-5 or greater"
+#else
 #include <folly/Poly.h>
 
 #include <folly/Conv.h>
@@ -560,3 +563,4 @@ TEST(Poly, Addable) {
   cc = aref + bref;
   EXPECT_EQ(6, poly_cast<int>(cc));
 }
+#endif
-- 
2.34.1