Lua exception handling test

[folly.git] / folly / Format.h

diff --git a/folly/Format.h b/folly/Format.h
index f87d90a95f4d46a1885f7fcac5a1436cb298b94f..d6fd2ff0c3a038d69da6783415aeda89f355b328 100644 (file)
--- a/folly/Format.h
+++ b/folly/Format.h
@@ -28,8 +28,8 @@
 #include <folly/Traits.h>
 
 // Ignore shadowing warnings within this file, so includers can use -Wshadow.
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wshadow"
+FOLLY_PUSH_WARNING
+FOLLY_GCC_DISABLE_WARNING("-Wshadow")
 
 namespace folly {
 
@@ -51,14 +51,20 @@ class FormatterTag {};
 /**
  * Formatter class.
  *
- * Note that this class is tricky, as it keeps *references* to its arguments
- * (and doesn't copy the passed-in format string).  Thankfully, you can't use
- * this directly, you have to use format(...) below.
+ * Note that this class is tricky, as it keeps *references* to its lvalue
+ * arguments (while it takes ownership of the temporaries), and it doesn't
+ * copy the passed-in format string. Thankfully, you can't use this
+ * directly, you have to use format(...) below.
  */
 
-/* BaseFormatter class. Currently, the only behavior that can be
- * overridden is the actual formatting of positional parameters in
+/* BaseFormatter class.
+ * Overridable behaviours:
+ * You may override the actual formatting of positional parameters in
  * `doFormatArg`. The Formatter class provides the default implementation.
+ *
+ * You may also override `doFormat` and `getSizeArg`. These override points were
+ * added to permit static analysis of format strings, when it is inconvenient
+ * or impossible to instantiate a BaseFormatter with the correct storage
  */
 template <class Derived, bool containerMode, class... Args>
 class BaseFormatter {
@@ -98,16 +104,19 @@ class BaseFormatter {
   }
 
   /**
-   * metadata to identify generated children of BaseFormatter
+   * Metadata to identify generated children of BaseFormatter
    */
   typedef detail::FormatterTag IsFormatter;
   typedef BaseFormatter BaseType;
 
  private:
-  typedef std::tuple<FormatValue<typename std::decay<Args>::type>...>
-      ValueTuple;
+  typedef std::tuple<Args...> ValueTuple;
   static constexpr size_t valueCount = std::tuple_size<ValueTuple>::value;
 
+  Derived const& asDerived() const {
+    return *static_cast<const Derived*>(this);
+  }
+
   template <size_t K, class Callback>
   typename std::enable_if<K == valueCount>::type
   doFormatFrom(size_t i, FormatArg& arg, Callback& /*cb*/) const {
@@ -118,7 +127,7 @@ class BaseFormatter {
   typename std::enable_if<(K < valueCount)>::type
   doFormatFrom(size_t i, FormatArg& arg, Callback& cb) const {
     if (i == K) {
-      static_cast<const Derived*>(this)->template doFormatArg<K>(arg, cb);
+      asDerived().template doFormatArg<K>(arg, cb);
     } else {
       doFormatFrom<K + 1>(i, arg, cb);
     }
@@ -157,7 +166,7 @@ class BaseFormatter {
       K<valueCount, int>::type getSizeArgFrom(size_t i, const FormatArg& arg)
           const {
     if (i == K) {
-      return getValue(std::get<K>(values_), arg);
+      return getValue(getFormatValue<K>(), arg);
     }
     return getSizeArgFrom<K + 1>(i, arg);
   }
@@ -179,10 +188,19 @@ class BaseFormatter {
   // for the exclusive use of format() (below).  This way, you can't create
   // a Formatter object, but can handle references to it (for streaming,
   // conversion to string, etc) -- which is good, as Formatter objects are
-  // dangerous (they hold references, possibly to temporaries)
+  // dangerous (they may hold references).
   BaseFormatter(BaseFormatter&&) = default;
   BaseFormatter& operator=(BaseFormatter&&) = default;
 
+  template <size_t K>
+  using ArgType = typename std::tuple_element<K, ValueTuple>::type;
+
+  template <size_t K>
+  FormatValue<typename std::decay<ArgType<K>>::type> getFormatValue() const {
+    return FormatValue<typename std::decay<ArgType<K>>::type>(
+        std::get<K>(values_));
+  }
+
   ValueTuple values_;
 };
 
@@ -196,11 +214,15 @@ class Formatter : public BaseFormatter<
       : BaseFormatter<
             Formatter<containerMode, Args...>,
             containerMode,
-            Args...>(str, std::forward<Args>(args)...) {}
+            Args...>(str, std::forward<Args>(args)...) {
+    static_assert(
+        !containerMode || sizeof...(Args) == 1,
+        "Exactly one argument required in container mode");
+  }
 
   template <size_t K, class Callback>
   void doFormatArg(FormatArg& arg, Callback& cb) const {
-    std::get<K>(this->values_).format(arg, cb);
+    this->template getFormatValue<K>().format(arg, cb);
   }
 
   friend class BaseFormatter<
@@ -447,4 +469,4 @@ vformatChecked(Str* out, StringPiece fmt, Container&& container) {
 
 #include <folly/Format-inl.h>
 
-#pragma GCC diagnostic pop
+FOLLY_POP_WARNING