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 mzscheme with

    mzscheme -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

(require trace)

Invoking the trace module sets the evaluation handler (via current-eval) to instrument Scheme source code.

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

(require trace/calltrace-lib)

The trace/calltrace-lib module provides functions that implement trace.

(instrumenting-enabled) → boolean?

(instrumenting-enabled on?) → void?

on? : any/c

A parameter that determines whether tracing instrumentation is enabled.

(calltrace-eval-handler e) → any

e : any/c

A procedure suitable for use with current-eval, which instruments expressions for Calltrace output (when instrumentation is not disabled via instrumenting-enabled).

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

(annotate e) → syntax?

e : any/c

Instruments the expression e with Calltrace support. This function is normally used by calltrace-eval-handler.