Macro Links

So far, we have shown that HyperCode displays functions, data types, and variables with links placed according to a simple paradigm: uses are linked to definitions, definitions to backtrace lists, and elements of backtrace lists back to uses. Preprocessor macros, however, require more sophisticated treatment, and in some circumstances complicate the treatment of functions, data types, and variables.

Macro definitions are handled much as function, data type, or variable definitions; HyperCode presents each macro definition with a link to a backtrace list of invocation sites, each element of which is linked in turn to the invocation site it describes.

However, macro uses are handled substantially differently than function, data type, or variable uses. Instead of being linked directly to a definition, each macro invocation in source code is linked to an expansion site where the macro's expansion is presented step-by-step (Figure 7). Simple macros may expand in one step; more complicated ones may expand through multiple levels of nesting as in Figure 7. The expansion site includes a links to the macro's definition. Any functions, data types, or variables exposed by the expansion of a macro are linked as if they had appeared in the code. For example, in Figure 8, the macro GENERIC_PTR, exposed by the expansion of the macro NULL_PTR, is linked to its definition as well as being expanded as part of the expansion of NULL_PTR.

Two important programmer advantages result from HyperCode macro expansion sites. First, as with functions, types, and variables, the basic set of links explicitly represent the network of relationships between preprocessor macros, making additions and alterations substantially easier to implement safely. Second, the exact expansion of a macro at a particular site is explicitly drawn out. A user need not search through each and every include file for the last applicable definition of a particular macro in order to discover its definition; nor need the user be fluent in ANSI specifications to correctly predict how a macro will expand.

When a macro expands to expose a function, variable, or data type use or definition, links that would have pointed to that site had it occurred explicitly in the code instead point to the macro invocation in the code; this mechanism makes it clear where in the context of the code the mention is made, and the mention itself can be exposed by following the link to the macro's expansion site.