RealView® Compilation Tools Linker and Utilities Guide 4.5. Using $Super$$ and $Sub$$ to override symbol definitions

4.5. Using $Super$$ and $Sub$$ to override symbol definitions

There are situations where an existing symbol cannot be modified because, for example, it is located in an external library or in ROM code.

Use the $Super$$ and $Sub$$ patterns to patch an existing symbol.

For example, to patch the definition of a function foo(), use $Super$$foo() and $Sub$$foo() as follows:

$Super$$foo: Identifies the original unpatched function foo(). Use this to call the original function directly.
$Sub$$foo: Identifies the new function that will be called instead of the original function foo(). Use this to add processing before or after the original function.

Example 4.6 shows the legacy function foo() modified to result in a call to ExtraFunc() and a call to foo(). For more details, see ARM ELF specification, aaelf.pdf, in install_directory\Documentation\Specifications\....

Example 4.6.

extern void ExtraFunc(void);
extern void $Super$$foo(void):

/* this function will be called instead of the original foo() */
void $Sub$$foo(void)
{
  ExtraFunc();    /* does some extra setup work */
  $Super$$foo();  /* calls the original foo() function */
}

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