Support -Werror=unused-function

Summary: Support `-Werror=unused-function`.

Reviewed By: Orvid, guangyfb

Differential Revision: D17252831

fbshipit-source-id: ccf3829ebaa6992341ff5b1ab84c173922eeae03

folly/experimental/exception_tracer/ExceptionTracer.cpp

@@ -23,6 +23,7 @@
 
 #include <glog/logging.h>
 
+#include <folly/CppAttributes.h>
 #include <folly/Portability.h>
 #include <folly/String.h>
 #include <folly/experimental/exception_tracer/ExceptionAbi.h>
@@ -107,12 +108,12 @@ namespace {
 struct ArmAbiTag {};
 struct AnyAbiTag {};
 
-bool isAbiCppException(ArmAbiTag, const char (&klazz)[8]) {
+FOLLY_MAYBE_UNUSED bool isAbiCppException(ArmAbiTag, const char (&klazz)[8]) {
   return klazz[4] == 'C' && klazz[5] == '+' && klazz[6] == '+' &&
       klazz[7] == '\0';
 }
 
-bool isAbiCppException(AnyAbiTag, const uint64_t& klazz) {
+FOLLY_MAYBE_UNUSED bool isAbiCppException(AnyAbiTag, const uint64_t& klazz) {
   // The least significant four bytes must be "C++\0"
   static const uint64_t cppClass =
       ((uint64_t)'C' << 24) | ((uint64_t)'+' << 16) | ((uint64_t)'+' << 8);

folly/functional/test/InvokeTest.cpp

@@ -16,6 +16,7 @@
 
 #include <folly/functional/Invoke.h>
 
+#include <folly/CppAttributes.h>
 #include <folly/portability/GTest.h>
 
 class InvokeTest : public testing::Test {};
@@ -72,7 +73,7 @@ char go(Obj const&, char const*) {
 namespace z {
 struct Obj {};
 } // namespace z
-float go(z::Obj const&, int) {
+FOLLY_MAYBE_UNUSED float go(z::Obj const&, int) {
   return 9;
 }
 

folly/logging/test/ConfigUpdateTest.cpp

@@ -40,13 +40,13 @@ MATCHER_P(LogHandlerMatcherImpl, config, "") {
  * A helper function to use in EXPECT_THAT() for matching a TestLogHandler
  * with the specified type and options.
  */
+auto MatchLogHandler(const LogHandlerConfig& config) {
+  return LogHandlerMatcherImpl(config);
+}
 auto MatchLogHandler(
     StringPiece type,
     std::unordered_map<std::string, std::string> options) {
-  return LogHandlerMatcherImpl(LogHandlerConfig{type, std::move(options)});
-}
-auto MatchLogHandler(const LogHandlerConfig& config) {
-  return LogHandlerMatcherImpl(config);
+  return MatchLogHandler(LogHandlerConfig{type, std::move(options)});
 }
 
 } // namespace

folly/test/ExpectedCoroutinesTest.cpp

@@ -109,7 +109,9 @@ TEST(Expected, CoroutineFailure) {
     co_return z;
   }();
   EXPECT_TRUE(r1.hasError());
+  EXPECT_NE(Err::bad(), r1.error());
   EXPECT_EQ(Err::badder(), r1.error());
+  EXPECT_NE(Err::baddest(), r1.error());
 }
 
 TEST(Expected, CoroutineException) {

folly/test/PolyTest.cpp

@@ -17,6 +17,7 @@
 #include <folly/Poly.h>
 
 #include <folly/Conv.h>
+#include <folly/CppAttributes.h>
 #include <folly/poly/Nullable.h>
 #include <folly/poly/Regular.h>
 #include <folly/portability/GTest.h>
@@ -718,7 +719,7 @@ struct Struct2 : Struct {
 int property(Struct const&) {
   return 42;
 }
-void property(Struct&, int) {}
+FOLLY_MAYBE_UNUSED void property(Struct&, int) {}
 
 int meow(Struct2&) {
   return 42;

folly/test/RangeTest.cpp

@@ -31,6 +31,7 @@
 #include <boost/algorithm/string/trim.hpp>
 #include <boost/range/concepts.hpp>
 
+#include <folly/CppAttributes.h>
 #include <folly/Memory.h>
 #include <folly/portability/GMock.h>
 #include <folly/portability/GTest.h>
@@ -1645,7 +1646,7 @@ class NonPOD {
  public:
   NonPOD() {}
 };
-void test_func(Range<const NonPOD*>) {}
+FOLLY_MAYBE_UNUSED void test_func(Range<const NonPOD*>) {}
 
 } // anonymous namespace
 

folly/test/sorted_vector_test.cpp

@@ -85,27 +85,6 @@ struct CountCopyCtor {
 
 int CountCopyCtor::gCount_ = 0;
 
-struct Opaque {
-  int value;
-  friend bool operator==(Opaque a, Opaque b) {
-    return a.value == b.value;
-  }
-  friend bool operator<(Opaque a, Opaque b) {
-    return a.value < b.value;
-  }
-  struct Compare : std::less<int>, std::less<Opaque> {
-    using is_transparent = void;
-    using std::less<int>::operator();
-    using std::less<Opaque>::operator();
-    bool operator()(int a, Opaque b) const {
-      return std::less<int>::operator()(a, b.value);
-    }
-    bool operator()(Opaque a, int b) const {
-      return std::less<int>::operator()(a.value, b);
-    }
-  };
-};
-
 } // namespace
 
 TEST(SortedVectorTypes, SetAssignmentInitListTest) {
@@ -605,16 +584,6 @@ TEST(SortedVectorTypes, EraseTest2) {
   EXPECT_EQ(m.size(), 5);
 }
 
-std::vector<int> extractValues(sorted_vector_set<CountCopyCtor> const& in) {
-  std::vector<int> ret;
-  std::transform(
-      in.begin(),
-      in.end(),
-      std::back_inserter(ret),
-      [](const CountCopyCtor& c) { return c.val_; });
-  return ret;
-}
-
 TEST(SortedVectorTypes, TestSetBulkInsertionSortMerge) {
   auto s = std::vector<int>({6, 4, 8, 2});