format: allow %! specifier for all types

If we allow the %! specifier for all types it greatly simplifies
handling of format strings in templated code, or code with non-trivial
typedefs.

format.ipp

@@ -88,6 +88,11 @@ namespace util { namespace format { namespace detail {
     };
 
 
+    ///////////////////////////////////////////////////////////////////////////
+    std::ostream&
+    operator<< (std::ostream &os, specifier::kind k);
+
+
     ///////////////////////////////////////////////////////////////////////////
     // provides the kind, a conversion specifier, and expected length for a
     // given type.
@@ -609,7 +614,7 @@ namespace util { namespace format { namespace detail {
         if (spec.k == specifier::kind::POINTER)
             return write (os, spec, reinterpret_cast<const void*> (t));
 
-        if (spec.k != specifier::kind::STRING)
+        if (spec.k != specifier::kind::STRING && spec.k != specifier::kind::OSTREAM)
             throw conversion_error ("invalid specifier kind for string argumetn");
 
         const auto len = spec.precision < 0                  ? spec.precision :
@@ -651,10 +656,10 @@ namespace util { namespace format { namespace detail {
     //-------------------------------------------------------------------------
     template <typename OutputT>
     OutputT
-    write (OutputT os, const specifier s, const char t)
+    write (OutputT os, const specifier spec, const char t)
     {
-        if (s.k != specifier::kind::CHARACTER)
+        if (spec.k != specifier::kind::CHARACTER && spec.k != specifier::kind::OSTREAM)
-            throw conversion_error ("invalid specifier kind for char argument");
+            throw conversion_error (render ("invalid specifier kind for char argument: %!", spec.k));
 
         *os = t;
         return ++os;
@@ -692,7 +697,7 @@ namespace util { namespace format { namespace detail {
     >
     write (OutputT &os, const specifier &spec, const T t)
     {
-        if (spec.k != specifier::kind::POINTER)
+        if (spec.k != specifier::kind::POINTER && spec.k != specifier::kind::OSTREAM)
             throw conversion_error ("invalid conversion specifier for pointer value");
 
         // glibc at least uses a special form for null pointers
@@ -730,15 +735,18 @@ namespace util { namespace format { namespace detail {
     >
     write (OutputT os, const specifier spec, ValueT t)
     {
-        if (spec.k == specifier::kind::POINTER && !t)
+        if (spec.k == specifier::kind::POINTER && !t) {
-        {
             return write (os, spec, reinterpret_cast<void*> (t));
         }
 
-        if (spec.k != (std::is_unsigned<ValueT>::value ? specifier::kind::UNSIGNED : specifier::kind::SIGNED))
+        if (!(spec.k == specifier::kind::UNSIGNED && std::is_unsigned<ValueT>::value ||
-            throw conversion_error ("invalid conversion specifier for integer value");
+              spec.k == specifier::kind::SIGNED   && std::is_signed  <ValueT>::value ||
+              spec.k == specifier::kind::OSTREAM))
+        {
+            throw conversion_error ("invalid conversion specifier for integer");
+        }
 
-        if (sizeof (ValueT) > spec.length)
+        if (sizeof (ValueT) > spec.length && spec.k != specifier::kind::OSTREAM)
             throw length_error ("overlength value parameter");
 
         const auto numerals   = digits (t, spec.base);
@@ -801,8 +809,13 @@ namespace util { namespace format { namespace detail {
         std::is_floating_point<T>::value,
         OutputT
     >
-    write (OutputT os, const specifier spec, T t)
+    write (OutputT os, specifier spec, T t)
     {
+        if (spec.k == specifier::kind::OSTREAM) {
+            spec   = specifier {};
+            spec.k = specifier::kind::REAL;
+        }
+
         if (spec.k != specifier::kind::REAL)
             throw conversion_error ("invalid conversion specifier for real value");
 
@@ -820,7 +833,8 @@ namespace util { namespace format { namespace detail {
             if (spec.left_adjusted)  *cursor++ = '-';
             if (spec.positive_char)  *cursor++ = spec.positive_char;
 
-            cursor += sprintf (cursor, "%u", spec.width);
+            if (spec.width)
+                cursor += sprintf (cursor, "%u", spec.width);
 
             if (spec.precision >= 0) {
                 *cursor++ = '.';

test/format.cpp

@@ -55,6 +55,7 @@ main (void)
     CHECK_RENDER ("%ju", "1",  (uintmax_t)1);
     CHECK_RENDER ("%zu", "0",  (size_t)0);
     CHECK_RENDER ("%zu", "1",  (size_t)1);
+    CHECK_RENDER ("%!", "1", 1u);
 
     CHECK_RENDER ("%o", "1", 01u);
     CHECK_RENDER ("%o", "13", 013u);
@@ -122,7 +123,10 @@ main (void)
     CHECK_RENDER ("%3.2f", "1.23", 1.2345678);
     CHECK_RENDER ("%3.2f", "1234.57", 1234.5678);
 
+    CHECK_RENDER ("%!", "1", 1.);
+
     CHECK_RENDER ("%c", "A", 'A');
+    CHECK_RENDER ("%!", "A", 'A');
 
     CHECK_RENDER ("%s", "foo", "foo");
     CHECK_RENDER ("%s", "foo", std::string ("foo"));
@@ -134,6 +138,8 @@ main (void)
     CHECK_RENDER ("%.64s", "foo", "foo");
     CHECK_RENDER ("%3.1s", "  f", "foo");
     CHECK_RENDER ("%-3.1s", "f  ", "foo");
+    CHECK_RENDER ("%!", "foo", "foo");
+
     CHECK_RENDER ("%!", "userobj", userobj {});
 
     CHECK_RENDER ("%p", "0x1234567", (void*)0x01234567);
@@ -141,6 +147,7 @@ main (void)
     CHECK_RENDER ("%p", "0x1234567", (char*)0x01234567);
     CHECK_RENDER ("%p", "(nil)", nullptr);
     CHECK_RENDER ("%p", "(nil)", NULL);
+    CHECK_RENDER ("%!", "0x1234567", (void*)0x01234567);
 
     CHECK_RENDER ("%%", "%");
     CHECK_RENDER ("%10%", "%");
@@ -202,6 +209,4 @@ main (void)
 
     CHECK_THROW("%c", conversion_error, 1u);
     CHECK_THROW("%c", conversion_error, "foo");
-
-    CHECK_THROW("%!", conversion_error, 1u);
 }