Update C++ style guide.

Mostly minor wording updates (e.g. preferring int64_t to int64). The
most significant change is clarifying the section on consistency to
clarify that consistency, in and of itself, should not be used as the
sole argument for blocking adoption of style changes.

cppguide.html

@@ -84,14 +84,20 @@ site). </dd>
 
 <dt>Be consistent with existing code</dt>
 <dd>Using one style consistently through our codebase lets us focus on
-other (more important) issues. Consistency also allows for
+other (more important) issues. Consistency also allows for automation:
-automation: tools that format your code or adjust
+tools that format your code or adjust your <code>#include</code>s only
-your <code>#include</code>s only work properly when your code is
+work properly when your code is consistent with the expectations of
-consistent with the expectations of the tooling. In many cases, rules
+the tooling. In many cases, rules that are attributed to "Be
-that are attributed to "Be Consistent" boil down to "Just pick one and
+Consistent" boil down to "Just pick one and stop worrying about it";
-stop worrying about it"; the potential value of allowing flexibility
+the potential value of allowing flexibility on these points is
-on these points is outweighed by the cost of having people argue over
+outweighed by the cost of having people argue over them. However,
-them. </dd>
+there are limits to consistency; it is a good tie breaker when there
+is no clear technical argument, nor a long-term direction. It applies
+more heavily locally (per file, or for a tightly-related set of
+interfaces). Consistency should not generally be used as a
+justification to do things in an old style without considering the
+benefits of the new style, or the tendency of the codebase to converge
+on newer styles over time.</dd>
 
 <dt>Be consistent with the broader C++ community when appropriate</dt>
 <dd>Consistency with the way other organizations use C++ has value for
@@ -1678,7 +1684,7 @@ be <code>protected</code> when using
 
 
 <a href="https://github.com/google/googletest">Google
-Test</a>).
+Test</a>.
 If a test fixture class is defined outside of the .cc file it is used in, for example in a .h file,
 make data members <code>private</code>.</p>
 
@@ -1695,7 +1701,7 @@ sections that would be empty.</p>
 <p>Within each section, prefer grouping similar
 kinds of declarations together, and prefer the
 following order: types (including <code>typedef</code>,
-<code>using</code>, and nested structs and classes),
+<code>using</code>, <code>enum</code>, and nested structs and classes),
 constants, factory functions, constructors and assignment
 operators, destructor, all other methods, data members.</p>
 
@@ -1730,6 +1736,8 @@ inputs, and use a <code>const</code> pointer when the non-optional form would
 have used a reference. Use non-<code>const</code> pointers to represent
 optional outputs and optional input/output parameters.</p>
 
+
+
 <p>
 Avoid defining functions that require a <code>const</code> reference parameter
 to outlive the call, because <code>const</code> reference parameters bind
@@ -2505,7 +2513,7 @@ workarounds disguise your true intent.</p>
 <p>Use C++-style casts
 like <code>static_cast&lt;float&gt;(double_value)</code>, or brace
 initialization for conversion of arithmetic types like
-<code>int64 y = int64{1} &lt;&lt; 42</code>. Do not use
+<code>int64_t y = int64_t{1} &lt;&lt; 42</code>. Do not use
 cast formats like <code>(int)x</code> unless the cast is to
 <code>void</code>. You may use cast formats like `T(x)` only when
 `T` is a class type.</p>
@@ -2534,7 +2542,7 @@ casts when explicit type conversion is necessary.
 
 <ul>
   <li>Use brace initialization to convert arithmetic types
-  (e.g., <code>int64{x}</code>).  This is the safest approach because code
+  (e.g., <code>int64_t{x}</code>).  This is the safest approach because code
   will not compile if conversion can result in information loss.  The
   syntax is also concise.</li>
 
@@ -2563,7 +2571,7 @@ casts when explicit type conversion is necessary.
   <li>Use <code>absl::bit_cast</code> to interpret the raw bits of a
   value using a different type of the same size (a type pun), such as
   interpreting the bits of a <code>double</code> as
-  <code>int64</code>.</li>
+  <code>int64_t</code>.</li>
 </ul>
 
 <p>See the <a href="#Run-Time_Type_Information__RTTI_">
@@ -2839,13 +2847,11 @@ enable their use with <code>constexpr</code>. Do not use
 <p>Of the built-in C++ integer types, the only one used
  is
 <code>int</code>. If a program needs a variable of a
-different size, use
+different size, use a precise-width integer type from
-a precise-width integer type from
 <code>&lt;stdint.h&gt;</code>, such as
 <code>int16_t</code>. If your variable represents a
 value that could ever be greater than or equal to 2^31
-(2GiB), use a 64-bit type such as
+(2GiB), use a 64-bit type such as <code>int64_t</code>.
-<code>int64_t</code>.
 Keep in mind that even if your value won't ever be too large
 for an <code>int</code>, it may be used in intermediate
 calculations which may require a larger type. When in doubt,
@@ -2867,17 +2873,6 @@ compiler and architecture.</p>
 
 <p class="decision"></p>
 
-<p>
-<code>&lt;cstdint&gt;</code> defines types
-like <code>int16_t</code>, <code>uint32_t</code>,
-<code>int64_t</code>, etc. You should always use
-those in preference to <code>short</code>, <code>unsigned
-long long</code> and the like, when you need a guarantee
-on the size of an integer. Of the C integer types, only
-<code>int</code> should be used. When appropriate, you
-are welcome to use standard types like
-<code>size_t</code> and <code>ptrdiff_t</code>.</p>
-
 <p>We use <code>int</code> very often, for integers we
 know are not going to be too big, e.g., loop counters.
 Use plain old <code>int</code> for such things. You
@@ -2885,18 +2880,14 @@ should assume that an <code>int</code> is
 
 at least 32 bits, but don't
 assume that it has more than 32 bits. If you need a 64-bit
-integer type, use
+integer type, use <code>int64_t</code> or <code>uint64_t</code>.
-<code>int64_t</code>
-or
-<code>uint64_t</code>.</p>
 
-<p>For integers we know can be "big",
+</p><p>For integers we know can be "big",
  use
 <code>int64_t</code>.
 </p>
 
 <p>You should not use the unsigned integer types such as
-
 <code>uint32_t</code>, unless there is a valid
 reason such as representing a bit pattern rather than a
 number, or you need defined overflow modulo 2^N. In
@@ -2967,7 +2958,6 @@ problems of printing, comparisons, and structure alignment.</p>
   specify a conversion for the standard bitwidth typedefs (e.g.,
   <code>int64_t</code>, <code>uint64_t</code>, <code>int32_t</code>,
   <code>uint32_t</code>, etc).
-
   Where possible, avoid passing arguments of types specified by bitwidth
   typedefs to <code>printf</code>-based APIs. Note that it is acceptable
   to use typedefs for which printf has dedicated length modifiers, such as
@@ -2982,8 +2972,7 @@ problems of printing, comparisons, and structure alignment.</p>
 
   <li>You may need to be careful with structure
   alignments, particularly for structures being stored on
-  disk. Any class/structure with a
+  disk. Any class/structure with a <code>int64_t</code>/<code>uint64_t</code>
-  <code>int64_t</code>/<code>uint64_t</code>
   member will by default end up being 8-byte aligned on a
   64-bit system. If you have such structures being shared
   on disk between 32-bit and 64-bit code, you will need
@@ -2998,13 +2987,9 @@ problems of printing, comparisons, and structure alignment.</p>
   <li>
   <p>Use <a href="#Casting">braced-initialization</a> as needed to create
   64-bit constants. For example:</p>
-
-
-<div>
 <pre>int64_t my_value{0x123456789};
 uint64_t my_mask{3ULL &lt;&lt; 48};
 </pre>
-</div>
   </li>
 </ul>
 
@@ -4651,7 +4636,7 @@ at the end of the line. These end-of-line comments should
 be separated from the code by 2 spaces. Example:</p>
 
 <pre>// If we have enough memory, mmap the data portion too.
-mmap_budget = max&lt;int64&gt;(0, mmap_budget - index_-&gt;length());
+mmap_budget = max&lt;int64_t&gt;(0, mmap_budget - index_-&gt;length());
 if (mmap_budget &gt;= data_size_ &amp;&amp; !MmapData(mmap_chunk_bytes, mlock))
   return;  // Error already logged.
 </pre>