Macros, Defines & Compilation · SystemVerilog

Part 7 · Advanced & Integration · Intermediate

4topics
4lessons

The SystemVerilog preprocessor runs before the compiler sees the code. ` define`, ifdef` and include`` do pure text substitution with no type checking and no scope.

Diagram

TOPIC MAP — PREPROCESSOR TO SIMULATOR

  source.sv ──► PREPROCESSOR ──► expanded text ──► COMPILER ──► ...
                    │
       ┌────────────┼──────────────┐
       │            │              │
       ▼            ▼              ▼
   `define       `ifdef        `include
   text macros  conditional    file paste
   (lesson 1)   compilation    + guards
                (lesson 2)     (lesson 3)
       │            │              │
       └────────────┴──────────────┘
                    │
                    ▼
        Debugging macro problems (lesson 4:
        expansion errors, loud guards, safe
        log macros, build stages)

Lesson	Covers
Text macros	Object-like and function-like macros, the parens rule, multiline bodies, and macros versus parameters.
Conditional compilation	` ifdef`` selection, command-line defines, sim-versus-synthesis guards, and configuration discipline.
Include guards	Textual paste semantics, the double-include failure, the guard pattern, and search paths.
Debugging macros	Expansion-error reading, loud configuration guards, a safe log macro, and build stages.

Check yourself One build prints a banner macro and another stays silent, with identical source files. Name two preprocessor-level causes.

A missing command-line define (` ifdef`` on a misspelled or unset name is silently false), or a macro redefined later in compile order so the second build expands a different body.

Up next`define & Text Macros

Practice this lesson Report an error

TOPIC MAP — PREPROCESSOR TO SIMULATOR source.sv ──► PREPROCESSOR ──► expanded text ──► COMPILER ──► ... │ ┌────────────┼──────────────┐ │ │ │ ▼ ▼ ▼ `define `ifdef `include text macros conditional file paste (lesson 1) compilation + guards (lesson 2) (lesson 3) │ │ │ └────────────┴──────────────┘ │ ▼ Debugging macro problems (lesson 4: expansion errors, loud guards, safe log macros, build stages)

Lesson

Covers

Text macros

Object-like and function-like macros, the parens rule, multiline bodies, and macros versus parameters.

Conditional compilation

` ifdef`` selection, command-line defines, sim-versus-synthesis guards, and configuration discipline.

Include guards

Textual paste semantics, the double-include failure, the guard pattern, and search paths.

Debugging macros

Expansion-error reading, loud configuration guards, a safe log macro, and build stages.