Manual: Add chapter about speeding up Cppcheck analysis

man/manual.md

@@ -593,6 +593,87 @@ Newline
 
 Carriage return
 
+## Speeding up Cppcheck
+
+It is possible to speed up Cppcheck analysis in a few different ways.
+
+### Preprocessor configurations
+
+Imagine this source code:
+
+    void foo()
+    {
+        int x;
+    #ifdef __GNUC__
+        x = 0;
+    #endif
+    #ifdef __MSCVER
+        x = 1;
+    #endif
+        return x;
+    }
+
+By default Cppcheck will try to check all the configurations. There are 3 important configurations here:
+ * Neither `__GNUC__` nor `__MSCVER` is defined
+ * `__GNUC__` is defined
+ * `__MSCVER` is defined
+
+When you run Cppcheck, the output will be something like:
+
+    $ cppcheck test.c
+    Checking test.c ...
+    [test.c:10]: (error) Uninitialized variable: x
+    Checking test.c: __GNUC__...
+    Checking test.c: __MSCVER...
+
+Now if you want you can limit the analysis. You probably know what the target compiler is. If `-D` is supplied and you do not specify `--force` then Cppcheck will only check the configuration you give.
+
+    $ cppcheck -D __GNUC__ test.c
+    Checking test.c ...
+    Checking test.c: __GNUC__=1...
+
+
+### Unused templates
+
+If you think Cppcheck is slow and you are using templates, then you should try how it works to remove unused templates.
+
+Imagine this code:
+
+    template <class T> struct Foo {
+        T x = 100;
+    };
+
+    template <class T> struct Bar {
+        T x = 200 / 0;
+    };
+
+    int main() {
+        Foo<int> foo;
+        return 0;
+    }
+
+Cppcheck says:
+
+    $ cppcheck test.cpp
+    Checking test.cpp ...
+    [test.cpp:7]: (error) Division by zero.
+
+It complains about division by zero in `Bar` even though `Bar` is not instantiated.
+
+You can use the option `--remove-unused-templates` to remove unused templates from Cppcheck analysis.
+
+Example:
+
+    $ cppcheck --remove-unused-templates test.cpp
+    Checking test.cpp ...
+
+This lost message is in theory not critical, since `Bar` is not instantiated the division by zero should not occur in your real program.
+
+The speedup you get can be remarkable.
+
+### Check headers
+
+TBD
 
 ## Misra