Trace: Instrumentation to Show Function Calls

Calltrace is a tool that displays all calls to user procedures. It displays the arguments to the calls, and it indents to show the depth of the continuation.

1 Quick Instructions

• Throw away ".zo" versions of your source

• Prefix your program with

  (require trace)

  perhaps by starting racket with
    racket -l trace ...
  before arguments to load your program.

• Run your program

The trace module is odd; don’t import it into another module. Instead, the trace module is meant to be invoked from the top-level, so that it can install an evaluation handler, exception handler, etc.

To reuse parts of the code of trace, import trace/calltrace-lib. It contains all of the bindings described here, but it but does not set the current-eval parameter.

2 Installing Calltrace

NOTE: trace has no effect on code loaded as compiled byte code (i.e., from a ".zo" file) or native code (i.e., from a ".dll", ".so", or ".dylib" file).

Calltrace’s instrumentation can be explicitly disabled via the instrumenting-enabled parameter. Instrumentation is on by default. The instrumenting-enabled parameter affects only the way that source code is compiled, not the way that exception information is reported.

Do not load trace before writing ".zo" files. Calltrace instruments S-expressions with unprintable values; this works fine if the instrumented S-expression is passed to the default eval handler, but neither the S-expression nor its byte-code form can be marshalled to a string.

3 Calltrace Library

Requiring trace installs this procedure as the value for current-eval.