Document PB_SYSTEM_HEADER

docs/index.rst

@@ -103,6 +103,8 @@ Nanopb should compile with most ansi-C compatible compilers. It however requires
 
 If these header files do not come with your compiler, you should be able to find suitable replacements online. Mostly the requirements are very simple, just a few basic functions and typedefs.
 
+Alternatively, you can define *PB_SYSTEM_HEADER*, which should be the name of a single header file including all the necessary definitions.
+
 Debugging and testing
 =====================
 Extensive unittests are included under the *tests* folder. Just type *make* there to run the tests.

docs/reference.rst

@@ -49,6 +49,11 @@ PB_BUFFER_ONLY                 Disables the support for custom streams. Only
 PB_OLD_CALLBACK_STYLE          Use the old function signature (void\* instead
                                of void\*\*) for callback fields. This was the
                                default until nanopb-0.2.1.
+PB_SYSTEM_HEADER               Replace the standard header files with a single
+                               header file. It should define all the required
+                               functions and typedefs listed on the
+                               `overview page`_. Value must include quotes,
+                               for example *#define PB_SYSTEM_HEADER "foo.h"*.
 ============================  ================================================
 
 The PB_MAX_REQUIRED_FIELDS, PB_FIELD_16BIT and PB_FIELD_32BIT settings allow
@@ -56,7 +61,7 @@ raising some datatype limits to suit larger messages. Their need is recognized
 automatically by C-preprocessor #if-directives in the generated .pb.h files.
 The default setting is to use the smallest datatypes (least resources used).
 
-
+.. _`overview page`: index.html#compiler-requirements
 
 
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