Use auto for scope-guard locals v.s. folly::ScopeGuard

Summary: Use `auto` for scope-guard locals v.s. `folly::ScopeGuard`.

Reviewed By: igorsugak, meyering

Differential Revision: D6664915

fbshipit-source-id: ea239b712f3f9dc7ef81105aaf82f4b36bc07db5

folly/ScopeGuard.h

 /*
- * Copyright 2017 Facebook, Inc.
+ * Copyright 2011-present Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -47,8 +47,7 @@ namespace folly {
  *
  *   // If the db insertion that follows fails, we should
  *   // remove it from memory.
- *   // (You could also declare this as "auto guard = makeGuard(...)")
- *   ScopeGuard guard = makeGuard([&] { friends_.pop_back(); });
+ *   auto guard = makeGuard([&] { friends_.pop_back(); });
  *
  *   // this will throw an exception upon error, which
  *   // makes the ScopeGuard execute UserCont::pop_back()

folly/experimental/symbolizer/Elf.cpp

@@ -76,7 +76,7 @@ int ElfFile::openNoThrow(
   // Always close fd and unmap in case of failure along the way to avoid
   // check failure above if we leave fd != -1 and the object is recycled
   // like it is inside SignalSafeElfCache
-  ScopeGuard guard = makeGuard([&] { reset(); });
+  auto guard = makeGuard([&] { reset(); });
   struct stat st;
   int r = fstat(fd_, &st);
   if (r == -1) {

folly/test/ScopeGuardTest.cpp

 /*
- * Copyright 2017 Facebook, Inc.
+ * Copyright 2011-present Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -23,7 +23,6 @@
 
 #include <folly/portability/GTest.h>
 
-using folly::ScopeGuard;
 using folly::makeGuard;
 using std::vector;
 
@@ -47,7 +46,7 @@ TEST(ScopeGuard, DifferentWaysToBind) {
   {
     // There is implicit conversion from func pointer
     // double (*)() to function<void()>.
-    ScopeGuard g = makeGuard(returnsDouble);
+    auto g = makeGuard(returnsDouble);
     (void)g;
   }
 
@@ -57,42 +56,42 @@ TEST(ScopeGuard, DifferentWaysToBind) {
   v.push_back(1);
   {
     // binding to member function.
-    ScopeGuard g = makeGuard(std::bind(&vector<int>::pop_back, &v));
+    auto g = makeGuard(std::bind(&vector<int>::pop_back, &v));
     (void)g;
   }
   EXPECT_EQ(0, v.size());
 
   {
     // bind member function with args. v is passed-by-value!
-    ScopeGuard g = makeGuard(std::bind(push_back, v, 2));
+    auto g = makeGuard(std::bind(push_back, v, 2));
     (void)g;
   }
   EXPECT_EQ(0, v.size()); // push_back happened on a copy of v... fail!
 
   // pass in an argument by pointer so to avoid copy.
   {
-    ScopeGuard g = makeGuard(std::bind(push_back, &v, 4));
+    auto g = makeGuard(std::bind(push_back, &v, 4));
     (void)g;
   }
   EXPECT_EQ(1, v.size());
 
   {
     // pass in an argument by reference so to avoid copy.
-    ScopeGuard g = makeGuard(std::bind(push_back, std::ref(v), 4));
+    auto g = makeGuard(std::bind(push_back, std::ref(v), 4));
     (void)g;
   }
   EXPECT_EQ(2, v.size());
 
   // lambda with a reference to v
   {
-    ScopeGuard g = makeGuard([&] { v.push_back(5); });
+    auto g = makeGuard([&] { v.push_back(5); });
     (void)g;
   }
   EXPECT_EQ(3, v.size());
 
   // lambda with a copy of v
   {
-    ScopeGuard g = makeGuard([v] () mutable { v.push_back(6); });
+    auto g = makeGuard([v]() mutable { v.push_back(6); });
     (void)g;
   }
   EXPECT_EQ(3, v.size());
@@ -101,7 +100,7 @@ TEST(ScopeGuard, DifferentWaysToBind) {
   int n = 0;
   {
     MyFunctor f(&n);
-    ScopeGuard g = makeGuard(f);
+    auto g = makeGuard(f);
     (void)g;
   }
   EXPECT_EQ(1, n);
@@ -109,7 +108,7 @@ TEST(ScopeGuard, DifferentWaysToBind) {
   // temporary functor object
   n = 0;
   {
-    ScopeGuard g = makeGuard(MyFunctor(&n));
+    auto g = makeGuard(MyFunctor(&n));
     (void)g;
   }
   EXPECT_EQ(1, n);
@@ -132,14 +131,9 @@ TEST(ScopeGuard, DifferentWaysToBind) {
 }
 
 TEST(ScopeGuard, GuardException) {
-  EXPECT_DEATH({
-    ScopeGuard g = makeGuard([&] {
-      throw std::runtime_error("destructors should never throw!");
-    });
-    (void)g;
-  },
-  "destructors should never throw!"
-  );
+  EXPECT_DEATH(
+      makeGuard([] { throw std::runtime_error("dtors should never throw!"); }),
+      "dtors should never throw!");
 }
 
 /**
@@ -155,7 +149,7 @@ void testUndoAction(bool failure) {
     v.push_back(1);
 
     // The guard is triggered to undo the insertion unless dismiss() is called.
-    ScopeGuard guard = makeGuard([&] { v.pop_back(); });
+    auto guard = makeGuard([&] { v.pop_back(); });
 
     // Do some action; Use the failure argument to pretend
     // if it failed or succeeded.
@@ -207,7 +201,7 @@ void testFinally(ErrorBehavior error) {
   bool cleanupOccurred = false;
 
   try {
-    ScopeGuard guard = makeGuard([&] { cleanupOccurred = true; });
+    auto guard = makeGuard([&] { cleanupOccurred = true; });
     (void)guard;
 
     try {

folly/test/function_benchmark/main.cpp

 /*
- * Copyright 2017 Facebook, Inc.
+ * Copyright 2011-present Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -23,7 +23,6 @@
 #include <folly/ScopeGuard.h>
 #include <folly/portability/GFlags.h>
 
-using folly::ScopeGuard;
 using folly::makeGuard;
 
 // Declare the bm_max_iters flag from folly/Benchmark.cpp
@@ -158,7 +157,7 @@ BENCHMARK(std_bind_direct_invoke, iters) {
 BENCHMARK(scope_guard_std_function, iters) {
   std::function<void()> fn(doNothing);
   for (size_t n = 0; n < iters; ++n) {
-    ScopeGuard g = makeGuard(fn);
+    auto g = makeGuard(fn);
     (void)g;
   }
 }
@@ -167,7 +166,7 @@ BENCHMARK(scope_guard_std_function, iters) {
 // but create the ScopeGuard with an rvalue to a std::function
 BENCHMARK(scope_guard_std_function_rvalue, iters) {
   for (size_t n = 0; n < iters; ++n) {
-    ScopeGuard g = makeGuard(std::function<void()>(doNothing));
+    auto g = makeGuard(std::function<void()>(doNothing));
     (void)g;
   }
 }
@@ -176,7 +175,7 @@ BENCHMARK(scope_guard_std_function_rvalue, iters) {
 // but create the ScopeGuard with an rvalue to a folly::Function
 BENCHMARK(scope_guard_Function_rvalue, iters) {
   for (size_t n = 0; n < iters; ++n) {
-    ScopeGuard g = makeGuard(folly::Function<void()>(doNothing));
+    auto g = makeGuard(folly::Function<void()>(doNothing));
     (void)g;
   }
 }
@@ -184,7 +183,7 @@ BENCHMARK(scope_guard_Function_rvalue, iters) {
 // Using ScopeGuard to invoke a function pointer
 BENCHMARK(scope_guard_fn_ptr, iters) {
   for (size_t n = 0; n < iters; ++n) {
-    ScopeGuard g = makeGuard(doNothing);
+    auto g = makeGuard(doNothing);
     (void)g;
   }
 }
@@ -192,7 +191,7 @@ BENCHMARK(scope_guard_fn_ptr, iters) {
 // Using ScopeGuard to invoke a lambda that does nothing
 BENCHMARK(scope_guard_lambda_noop, iters) {
   for (size_t n = 0; n < iters; ++n) {
-    ScopeGuard g = makeGuard([] {});
+    auto g = makeGuard([] {});
     (void)g;
   }
 }
@@ -200,7 +199,7 @@ BENCHMARK(scope_guard_lambda_noop, iters) {
 // Using ScopeGuard to invoke a lambda that invokes a function
 BENCHMARK(scope_guard_lambda_function, iters) {
   for (size_t n = 0; n < iters; ++n) {
-    ScopeGuard g = makeGuard([] { doNothing(); });
+    auto g = makeGuard([] { doNothing(); });
     (void)g;
   }
 }
@@ -209,7 +208,7 @@ BENCHMARK(scope_guard_lambda_function, iters) {
 BENCHMARK(scope_guard_lambda_local_var, iters) {
   uint32_t count = 0;
   for (size_t n = 0; n < iters; ++n) {
-    ScopeGuard g = makeGuard([&] {
+    auto g = makeGuard([&] {
       // Increment count if n is odd.  Without this conditional check
       // (i.e., if we just increment count each time through the loop),
       // gcc is smart enough to optimize the entire loop away, and just set