Pass errors to handler instead of throwing (#566)

.travis.yml

@@ -14,13 +14,24 @@ env:
         6pxmyzLHSn1ZR7OX5rfPvwM3tOyZ3H0=
   matrix:
     - BUILD=Doc
-    - BUILD=Debug STANDARD=0x
-    - BUILD=Release STANDARD=0x
+    - BUILD=Debug STANDARD=14
+    - BUILD=Release STANDARD=14
 
 matrix:
   exclude:
     - os: osx
       env: BUILD=Doc
 
+# Install gcc-6 for extended constexpr support.
+addons:
+  apt:
+    sources:
+    - ubuntu-toolchain-r-test
+    packages:
+    - g++-6
+
+before_install:
+  - export CXX=g++-6
+
 script:
   - support/travis-build.py

fmt/format.h

@@ -3100,9 +3100,15 @@ struct precision_handler {
   }
 };
 
+struct error_handler {
+  void on_error(const char *message) {
+    FMT_THROW(format_error(message));
+  }
+};
+
 // A format specifier handler that sets fields in basic_format_specs.
 template <typename Char>
-class specs_setter {
+class specs_setter : public error_handler {
  public:
   explicit specs_setter(basic_format_specs<Char> &specs): specs_(specs) {}
 
@@ -3316,12 +3322,6 @@ class dynamic_specs_handler :
   ParseContext &context_;
 };
 
-struct error_handler {
-  void on_error(const char *message) {
-    FMT_THROW(format_error(message));
-  }
-};
-
 template <typename Iterator, typename Handler>
 constexpr Iterator parse_arg_id(Iterator it, Handler& handler) {
   using char_type = typename std::iterator_traits<Iterator>::value_type;
@@ -3358,7 +3358,7 @@ constexpr Iterator parse_arg_id(Iterator it, Handler& handler) {
 //     format specifiers.
 template <typename Iterator, typename Handler>
 Iterator parse_format_specs(Iterator it, Handler &handler) {
-  using char_type = typename Iterator::value_type;
+  using char_type = typename std::iterator_traits<Iterator>::value_type;
   // Parse fill and alignment.
   if (char_type c = *it) {
     auto p = it + 1;
@@ -3382,8 +3382,10 @@ Iterator parse_format_specs(Iterator it, Handler &handler) {
         handler.on_align(align);
         if (p != it) {
           if (c == '}') break;
-          if (c == '{')
-            FMT_THROW(format_error("invalid fill character '{'"));
+          if (c == '{') {
+            handler.on_error("invalid fill character '{'");
+            return it;
+          }
           it += 2;
           handler.on_fill(c);
         } else ++it;
@@ -3423,7 +3425,7 @@ Iterator parse_format_specs(Iterator it, Handler &handler) {
   if ('0' <= *it && *it <= '9') {
     handler.on_width(parse_nonnegative_int(it));
   } else if (*it == '{') {
-    struct width_handler : error_handler {
+    struct width_handler {
       explicit width_handler(Handler &h) : handler(h) {}
 
       void operator()() { handler.on_dynamic_width(auto_id()); }
@@ -3432,11 +3434,17 @@ Iterator parse_format_specs(Iterator it, Handler &handler) {
         handler.on_dynamic_width(id);
       }
 
+      void on_error(const char *message) {
+        handler.on_error(message);
+      }
+
       Handler &handler;
     } wh(handler);
     it = parse_arg_id(it + 1, wh);
-    if (*it++ != '}')
-      FMT_THROW(format_error("invalid format string"));
+    if (*it++ != '}') {
+      handler.on_error("invalid format string");
+      return it;
+    }
   }
 
   // Parse precision.
@@ -3445,7 +3453,7 @@ Iterator parse_format_specs(Iterator it, Handler &handler) {
     if ('0' <= *it && *it <= '9') {
       handler.on_precision(parse_nonnegative_int(it));
     } else if (*it == '{') {
-      struct precision_handler : error_handler {
+      struct precision_handler {
         explicit precision_handler(Handler &h) : handler(h) {}
 
         void operator()() { handler.on_dynamic_precision(auto_id()); }
@@ -3454,13 +3462,20 @@ Iterator parse_format_specs(Iterator it, Handler &handler) {
           handler.on_dynamic_precision(id);
         }
 
+        void on_error(const char *message) {
+          handler.on_error(message);
+        }
+
         Handler &handler;
       } ph(handler);
       it = parse_arg_id(it + 1, ph);
-      if (*it++ != '}')
-        FMT_THROW(format_error("invalid format string"));
+      if (*it++ != '}') {
+        handler.on_error("invalid format string");
+        return it;
+      }
     } else {
-      FMT_THROW(format_error("missing precision specifier"));
+      handler.on_error("missing precision specifier");
+      return it;
     }
     handler.end_precision();
   }

support/cmake/cxx14.cmake

@@ -49,6 +49,7 @@ if (CMAKE_CXX_STANDARD)
   set(CPP14_FLAG )
 endif ()
 
+message(STATUS "CPP14_FLAG: ${CPP14_FLAG}")
 set(CMAKE_REQUIRED_FLAGS ${CPP14_FLAG})
 
 # Check if variadic templates are working and not affected by GCC bug 39653:

support/travis-build.py

@@ -89,10 +89,8 @@ common_cmake_flags = [
     '-DCMAKE_INSTALL_PREFIX=' + install_dir, '-DCMAKE_BUILD_TYPE=' + build
 ]
 extra_cmake_flags = []
-if standard != '0x':
-    extra_cmake_flags = [
-        '-DCMAKE_CXX_FLAGS=-std=c++' + standard, '-DFMT_USE_CPP11=OFF'
-    ]
+if standard != '14':
+    extra_cmake_flags = ['-DCMAKE_CXX_FLAGS=-std=c++' + standard]
 check_call(['cmake', '-DFMT_DOC=OFF', '-DFMT_PEDANTIC=ON', fmt_dir] +
            common_cmake_flags + extra_cmake_flags, cwd=build_dir)