Add a <<fundamentals-strings, String Representation>> section clarifying (#2365)

that UTF-8 strings returned from queries in fixed-length buffers will
always include the null terminator in that buffer (public issue 2351).

2 files changed, 43 insertions, 3 deletions

diff --git a/appendices/vulkanscdeviations.adoc b/appendices/vulkanscdeviations.adoc
index b20acf64..a4efa00d 100644
--- a/appendices/vulkanscdeviations.adoc
+++ b/appendices/vulkanscdeviations.adoc
@@ -181,8 +181,8 @@ a framework for handling deviations.
 |Directive  |4.6: "_typedefs_ that indicate size and signedness should be used
              in place of the basic numerical types"
 |Category   |Advisory
-|Note       |This is reported for every `char` and `float` variable used in the
-             API.
+|Note       |This is reported for every code:char and code:float variable
+             used in the API.
 |Rationale  |Vulkan SC maintains the Base Vulkan type conventions for
              compatibility between APIs.
 |===
diff --git a/chapters/fundamentals.adoc b/chapters/fundamentals.adoc
index 5f611b41..2a55e2b8 100644
--- a/chapters/fundamentals.adoc
+++ b/chapters/fundamentals.adoc
@@ -965,10 +965,15 @@ a structure) satisfy the alignment requirements of the host processor.
 [[fundamentals-validusage-strings]]
 ==== Valid Usage for Strings
 
-Any parameter that is a pointer to `char` must: be a finite sequence of
+Any parameter that is a pointer to code:char must: be a finite sequence of
 values terminated by a null character, or if _explicitly called out in the
 Specification_, can: be `NULL`.
 
+Strings specified as UTF-8 encoded must: not contain invalid UTF-8
+sequences.
+See <<fundamentals-strings, String Representation>> for additional
+information about strings.
+
 
 [[fundamentals-validusage-enums]]
 ==== Valid Usage for Enumerated Types
@@ -1815,6 +1820,41 @@ This equation is used everywhere that floating-point values are converted to
 signed normalized fixed-point.
 
 
+[[fundamentals-strings]]
+== String Representation
+
+Strings passed into and returned from Vulkan API commands are usually
+defined to be null-terminated and UTF-8 encoded.
+
+[NOTE]
+.Note
+====
+Exceptions to this rule exist only when strings are defined or used by
+operating system APIs where that OS has a different convention.
+For example, slink:VkExportMemoryWin32HandleInfoKHR::pname:name is a
+null-terminated UTF-16 encoded string used in conjunction with Windows
+handles.
+====
+
+When a UTF-8 string is *returned from* a Vulkan API query, it is returned in
+a fixed-length buffer of C code:char.
+For example, a string returned in
+slink:VkPhysicalDeviceProperties::pname:deviceName has maximum length
+ename:VK_MAX_PHYSICAL_DEVICE_NAME_SIZE, and a string returned in
+slink:VkExtensionProperties::pname:extensionName has maximum length
+ename:VK_MAX_EXTENSION_NAME_SIZE.
+The string, *including* its null terminator, will always fit completely
+within this buffer.
+If the string is shorter than the buffer size, the contents of code:char
+in the buffer following the null terminator are undefined:.
+
+When a UTF-8 string is *passed into* a Vulkan API, such as
+slink:VkDeviceCreateInfo::pname:ppEnabledExtensionNames, there is no
+explicit limit on the length of that string.
+However, the string must: contain a valid UTF-8 encoded string and must: be
+null-terminated.
+
+
 [[fundamentals-common-objects]]
 == Common Object Types