Enable -Wunreachable-code

Summary:
Because it finds dead code.
This also removes the dead code found.

Reviewed By: yfeldblum

Differential Revision: D4310312

fbshipit-source-id: 8178dacc9268e1001efc5f803a35ef49e23d692a

diff --git a/folly/Benchmark.cpp b/folly/Benchmark.cpp
index ccae03448d064bebf3432e9e2f93ee9eeff4e5f8..6c481335a63eaee06a1129873b8f3a68c865e4de 100644 (file)
--- a/folly/Benchmark.cpp
+++ b/folly/Benchmark.cpp
@@ -139,41 +139,6 @@ meanVariance(const double * begin, const double *const end) {
   return make_pair(sum / n, sqrt((sum2 - sum * sum / n) / n));
 }
 
-/**
- * Computes the mode of a sample set through brute force. Assumes
- * input is sorted.
- */
-static double mode(const double * begin, const double *const end) {
-  assert(begin < end);
-  // Lower bound and upper bound for result and their respective
-  // densities.
-  auto
-    result = 0.0,
-    bestDensity = 0.0;
-
-  // Get the variance so we pass it down to density()
-  auto const sigma = meanVariance(begin, end).second;
-  if (!sigma) {
-    // No variance means constant signal
-    return *begin;
-  }
-
-  FOR_EACH_RANGE (i, begin, end) {
-    assert(i == begin || *i >= i[-1]);
-    auto candidate = density(begin, end, *i, sigma * sqrt(2.0));
-    if (candidate > bestDensity) {
-      // Found a new best
-      bestDensity = candidate;
-      result = *i;
-    } else {
-      // Density is decreasing... we could break here if we definitely
-      // knew this is unimodal.
-    }
-  }
-
-  return result;
-}
-
 /**
  * Given a bunch of benchmark samples, estimate the actual run time.
  */
@@ -182,55 +147,7 @@ static double estimateTime(double * begin, double * end) {
 
   // Current state of the art: get the minimum. After some
   // experimentation, it seems taking the minimum is the best.
-
   return *min_element(begin, end);
-
-  // What follows after estimates the time as the mode of the
-  // distribution.
-
-  // Select the awesomest (i.e. most frequent) result. We do this by
-  // sorting and then computing the longest run length.
-  sort(begin, end);
-
-  // Eliminate outliers. A time much larger than the minimum time is
-  // considered an outlier.
-  while (end[-1] > 2.0 * *begin) {
-    --end;
-    if (begin == end) {
-      LOG(INFO) << *begin;
-    }
-    assert(begin < end);
-  }
-
-  double result = 0;
-
-  /* Code used just for comparison purposes */ {
-    unsigned bestFrequency = 0;
-    unsigned candidateFrequency = 1;
-    double candidateValue = *begin;
-    for (auto current = begin + 1; ; ++current) {
-      if (current == end || *current != candidateValue) {
-        // Done with the current run, see if it was best
-        if (candidateFrequency > bestFrequency) {
-          bestFrequency = candidateFrequency;
-          result = candidateValue;
-        }
-        if (current == end) {
-          break;
-        }
-        // Start a new run
-        candidateValue = *current;
-        candidateFrequency = 1;
-      } else {
-        // Cool, inside a run, increase the frequency
-        ++candidateFrequency;
-      }
-    }
-  }
-
-  result = mode(begin, end);
-
-  return result;
 }
 
 static double runBenchmarkGetNSPerIteration(const BenchmarkFun& fun,

diff --git a/folly/dynamic.cpp b/folly/dynamic.cpp
index 5e656c5e2d2acb0ce461942e9a88cbeefe295335..e9a37a991207d865f1dc4a013c4b254a3c02e4ca 100644 (file)
--- a/folly/dynamic.cpp
+++ b/folly/dynamic.cpp
@@ -14,8 +14,10 @@
  * limitations under the License.
  */
 
-#include <folly/Hash.h>
 #include <folly/dynamic.h>
+
+#include <folly/Assume.h>
+#include <folly/Hash.h>
 #include <folly/portability/BitsFunctexcept.h>
 
 namespace folly {
@@ -277,9 +279,8 @@ std::size_t dynamic::hash() const {
     const auto& str = getString();
     return ::folly::hash::fnv32_buf(str.data(), str.size());
   }
-  default:
-    CHECK(0); abort();
   }
+  assume_unreachable();
 }
 
 char const* dynamic::typeName(Type t) {

diff --git a/folly/experimental/DynamicParser.cpp b/folly/experimental/DynamicParser.cpp
index 18dd25fd1b5baab04ca6412e9f9c13618cf29ec7..734013c90fdda8d1d42f79e55f9ddbb3ce915366 100644 (file)
--- a/folly/experimental/DynamicParser.cpp
+++ b/folly/experimental/DynamicParser.cpp
@@ -96,7 +96,6 @@ void DynamicParser::reportError(
       break;  // Continue parsing
     case OnError::THROW:
       stack_.throwErrors();  // Package releaseErrors() into an exception.
-      LOG(FATAL) << "Not reached";  // silence lint false positive
     default:
       LOG(FATAL) << "Bad onError_: " << static_cast<int>(onError_);
   }

diff --git a/folly/experimental/exception_tracer/ExceptionTracerLib.cpp b/folly/experimental/exception_tracer/ExceptionTracerLib.cpp
index 2ba97b7843f55818e960bfefad39db39611b9106..a0a60dd308b4ab94272dc8aa3eb9f77ac2ef736f 100644 (file)
--- a/folly/experimental/exception_tracer/ExceptionTracerLib.cpp
+++ b/folly/experimental/exception_tracer/ExceptionTracerLib.cpp
@@ -28,13 +28,12 @@
 namespace __cxxabiv1 {
 
 extern "C" {
-void __cxa_throw(
+[[noreturn]] void __cxa_throw(
     void* thrownException,
     std::type_info* type,
-    void (*destructor)(void*)) __attribute__((__noreturn__));
+    void (*destructor)(void*));
 void* __cxa_begin_catch(void* excObj) throw();
-void __cxa_rethrow(void) __attribute__((__noreturn__));
-void __cxa_rethrow(void);
+[[noreturn]] void __cxa_rethrow(void);
 void __cxa_end_catch(void);
 }
 
@@ -90,17 +89,17 @@ DECLARE_CALLBACK(RethrowException);
 
 namespace __cxxabiv1 {
 
-void __cxa_throw(void* thrownException,
-                 std::type_info* type,
-                 void (*destructor)(void*)) {
+[[noreturn]] void __cxa_throw(void* thrownException,
+                              std::type_info* type,
+                              void (*destructor)(void*)) {
   static auto orig_cxa_throw =
       reinterpret_cast<decltype(&__cxa_throw)>(dlsym(RTLD_NEXT, "__cxa_throw"));
   getCxaThrowCallbacks().invoke(thrownException, type, destructor);
   orig_cxa_throw(thrownException, type, destructor);
-  __builtin_unreachable(); // orig_cxa_throw never returns
+  __builtin_unreachable();
 }
 
-void __cxa_rethrow() {
+[[noreturn]] void __cxa_rethrow() {
   // __cxa_rethrow leaves the current exception on the caught stack,
   // and __cxa_begin_catch recognizes that case.  We could do the same, but
   // we'll implement something simpler (and slower): we pop the exception from
@@ -110,7 +109,7 @@ void __cxa_rethrow() {
       dlsym(RTLD_NEXT, "__cxa_rethrow"));
   getCxaRethrowCallbacks().invoke();
   orig_cxa_rethrow();
-  __builtin_unreachable(); // orig_cxa_rethrow never returns
+  __builtin_unreachable();
 }
 
 void* __cxa_begin_catch(void* excObj) throw() {
@@ -143,7 +142,10 @@ void rethrow_exception(std::exception_ptr ep) {
                 "_ZSt17rethrow_exceptionNSt15__exception_ptr13exception_ptrE"));
   getRethrowExceptionCallbacks().invoke(ep);
   orig_rethrow_exception(ep);
-  __builtin_unreachable(); // orig_rethrow_exception never returns
+  // Clang knows this is unreachable, but GCC doesn't.
+#ifndef __clang__
+  __builtin_unreachable();
+#endif
 }
 
 } // namespace std

diff --git a/folly/fibers/test/FibersTest.cpp b/folly/fibers/test/FibersTest.cpp
index d1b60cee6b13c69f9236dce3f4a20a9e49a6f064..1577b5d30c695eb60d90008cae52f7c12ca09d28 100644 (file)
--- a/folly/fibers/test/FibersTest.cpp
+++ b/folly/fibers/test/FibersTest.cpp
@@ -1963,7 +1963,7 @@ TEST(FiberManager, ABD_DispatcherDestroyedBeforeCallingCommit) {
     dispatchJobs(executor, jobs, results);
     throw std::runtime_error(
         "Unexpected exception in user code before commit called");
-    atomicBatchDispatcher.commit();
+    // atomicBatchDispatcher.commit();
   } catch (...) {
     /* User code handles the exception and does not exit process */
   }