Tornado

5
Shell
5.4 C++ Interpretation
Tornado supports both C and C++ as development languages; see VxWorks
Programmer’s Guide: C++ Development for information about C++ development.
Because C and C++ expressions are so similar, the WindSh C-expression
interpreter supports many C++ expressions. The facilities explained in 5.3 The Shell
C-Expression Interpreter, p.174 are all available regardless of whether your source
language is C or C++. In addition, there are a few special facilities for C++
extensions. This section describes those extensions.
However, WindSh is not a complete interpreter for C++ expressions. In particular,
the shell has no information about user-defined types; there is no support for the ::
operator; constructors, destructors, and operator functions cannot be called
directly from the shell; and member functions cannot be called with the . or ->
operators.
To exercise C++ facilities that are missing from the C-expression interpreter, you
can compile and download routines that encapsulate the special C++ syntax.
Fortunately, the Tornado dynamic linker makes this relatively painless.
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5.4.1 Overloaded Function Names
If you have several C++ functions with the same name, distinguished by their
argument lists, call any of them as usual with the name they share. When the shell
detects the fact that several functions exist with the specified name, it lists them in
an interactive dialogue, printing the matching functions’ signatures so that you
can recall the different versions and make a choice among them.
You make your choice by entering the number of the desired function. If you make
an invalid choice, the list is repeated and you are prompted to choose again. If you
enter 0 (zero), the shell stops evaluating the current command and prints a
message like the following, with xxx replaced by the function name you entered:
undefined symbol: xxx
This can be useful, for example, if you misspelled the function name and you want
to abandon the interactive dialogue. However, because WindSh is an interpreter,
portions of the expression may already have executed (perhaps with side effects)
before you abandon execution in this way.
The following example shows how the support for overloaded names works. In
this example, there are four versions of a function called xmin( ). Each version of
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