allow AsyncSignalHandler to attach and detach from an EventBase

[folly.git] / folly / io / Cursor.h

diff --git a/folly/io/Cursor.h b/folly/io/Cursor.h
index 516b10393be3dae1c050651676584706d5a36e57..23186764da40f631ae59b7f60b5bb9ca1a14cfd7 100644 (file)
--- a/folly/io/Cursor.h
+++ b/folly/io/Cursor.h
@@ -227,7 +227,7 @@ class CursorBase {
 
   template <class T>
   T read() {
-    T val;
+    T val{};
     if (!tryRead(val)) {
       std::__throw_out_of_range("underflow");
     }
@@ -439,7 +439,7 @@ class CursorBase {
 
   size_t cloneAtMost(std::unique_ptr<folly::IOBuf>& buf, size_t len) {
     if (!buf) {
-      buf = make_unique<folly::IOBuf>();
+      buf = std::make_unique<folly::IOBuf>();
     }
     return cloneAtMost(*buf, len);
   }
@@ -756,6 +756,14 @@ class RWCursor
 
   using detail::Writable<RWCursor<access>>::pushAtMost;
   size_t pushAtMost(const uint8_t* buf, size_t len) {
+    // We have to explicitly check for an input length of 0.
+    // We support buf being nullptr in this case, but we need to avoid calling
+    // memcpy() with a null source pointer, since that is undefined behavior
+    // even if the length is 0.
+    if (len == 0) {
+      return 0;
+    }
+
     size_t copied = 0;
     for (;;) {
       // Fast path: the current buffer is big enough.
@@ -884,6 +892,14 @@ class Appender : public detail::Writable<Appender> {
 
   using detail::Writable<Appender>::pushAtMost;
   size_t pushAtMost(const uint8_t* buf, size_t len) {
+    // We have to explicitly check for an input length of 0.
+    // We support buf being nullptr in this case, but we need to avoid calling
+    // memcpy() with a null source pointer, since that is undefined behavior
+    // even if the length is 0.
+    if (len == 0) {
+      return 0;
+    }
+
     size_t copied = 0;
     for (;;) {
       // Fast path: it all fits in one buffer.