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critcl::cutil(n) 0.3 doc "C Runtime In Tcl (CriTcl)"

Name

critcl::cutil - CriTcl - C-level Utilities

Table Of Contents

Synopsis

  • package require Tcl 8.6
  • package require critcl ?3.2?
  • package require critcl::cutil ?0.3?

Description

Be welcome to the C Runtime In Tcl (short: CriTcl), a system for embedding and using C code from within Tcl scripts.

This document is the reference manpage for the critcl::cutil package. This package encapsulates a number of C-level utilites for easier writing of memory allocations, assertions, and narrative tracing and provides convenience commands to make these utilities accessible to critcl projects. Its intended audience are mainly developers wishing to write Tcl packages with embedded C code.

This package resides in the Core Package Layer of CriTcl.

arch_core

The reason for this is that the main critcl package makes use of the facilities for narrative tracing when critcl::config trace is set, to instrument commands and procedures.

API

::critcl::cutil::alloc

This command provides a number C-preprocessor macros which make the writing of memory allocations for structures and arrays of structures easier.

When run the header file "critcl_alloc.h" is directly made available to the ".critcl" file containing the command, and becomes available for use in #include directives of companion C code declared via critcl::csources.

The macros definitions and their signatures are:

    type* ALLOC (type)
    type* ALLOC_PLUS (type, int n)
    type* NALLOC (type, int n)
    type* REALLOC (type* var, type, int n)
    void  FREE (type* var)
    void STREP    (Tcl_Obj* o, char* s, int len);
    void STREP_DS (Tcl_Obj* o, Tcl_DString* ds);
    void STRDUP   (varname, char* str);

The details of the semantics are explained in section Allocation.

The result of the command is an empty string.

::critcl::cutil::assertions ?enable?

This command provides a number C-preprocessor macros for the writing of assertions in C code.

When invoked the header file "critcl_assert.h" is directly made available to the ".critcl" file containing the command, and becomes available for use in #include directives of companion C code declared via critcl::csources.

The macro definitions and their signatures are

    void ASSERT (expression, char* message);
    void ASSERT_BOUNDS (int index, int size);
    void STOPAFTER (int n);

Note that these definitions are conditional on the existence of the macro CRITCL_ASSERT. Without a critcl::cflags -DCRITCL_ASSERT all assertions in the C code are quiescent and not compiled into the object file. In other words, assertions can be (de)activated at will during build time, as needed by the user.

For convenience this is controlled by enable. By default (false) the facility available, but not active. Using true not only makes it available, but activates it as well.

The details of the semantics are explained in section Assertions.

The result of the command is an empty string.

::critcl::cutil::tracer ?enable?

This command provides a number C-preprocessor macros for tracing C-level internals.

When invoked the header file "critcl_trace.h" is directly made available to the ".critcl" file containing the command, and becomes available for use in #include directives of companion C code declared via critcl::csources. Furthermore the ".c" file containing the runtime support is added to the set of C companion files

The macro definitions and their signatures are

    /* (de)activation of named logical streams.
     * These are declarators, not statements.
     */
    TRACE_ON;
    TRACE_OFF;
    TRACE_TAG_ON  (tag_identifier);
    TRACE_TAG_OFF (tag_identifier);
    /*
     * Higher level trace statements (convenience commands)
     */
    void TRACE_FUNC   (const char* format, ...);
    void TRACE_FUNC_VOID;
    any  TRACE_RETURN (const char* format, any x);
    void TRACE_RETURN_VOID;
    void TRACE (const char* format, ...);
    /*
     * Low-level trace statements the higher level ones above
     * are composed from. Scope management and output management.
     */
    void TRACE_PUSH_SCOPE (const char* scope);
    void TRACE_PUSH_FUNC;
    void TRACE_POP;
    void TRACE_HEADER (int indent);
    void TRACE_ADD (const char* format, ...);
    void TRACE_CLOSER;
    /*
     * Convert tag to the underlying status variable.
     */
    TRACE_TAG_VAR (tag)
    /*
     * Conditional use of arbitrary code.
     */
    TRACE_RUN (code);
    TRACE_DO (code);
    TRACE_TAG_DO (code);

Note that these definitions are conditional on the existence of the macro CRITCL_TRACER. Without a critcl::cflags -DCRITCL_TRACER all trace functionality in the C code is quiescent and not compiled into the object file. In other words, tracing can be (de)activated at will during build time, as needed by the user.

For convenience this is controlled by enable. By default (false) the facility available, but not active. Using true not only makes it available, but activates it as well. Further note that the command critcl::config now accepts a boolean option trace. Setting it activates enter/exit tracing in all commands based on critcl::cproc, with proper printing of arguments and results. This implicitly activates the tracing facility in general.

The details of the semantics are explained in section Tracing

The result of the command is an empty string.

Allocation

type* ALLOC (type)

This macro allocates a single element of the given type and returns a pointer to that memory.

type* ALLOC_PLUS (type, int n)

This macro allocates a single element of the given type, plus an additional n bytes after the structure and returns a pointer to that memory.

This is for variable-sized structures of. An example of such could be a generic list element structure which stores management information in the structure itself, and the value/payload immediately after, in the same memory block.

type* NALLOC (type, int n)

This macro allocates n elements of the given type and returns a pointer to that memory.

type* REALLOC (type* var, type, int n)

This macro expands or shrinks the memory associated with the C variable var of type type to hold n elements of the type. It returns a pointer to that memory. Remember, a reallocation may move the data to a new location in memory to satisfy the request. Returning a pointer instead of immediately assigning it to the var allows the user to validate the new pointer before trying to use it.

void FREE (type* var)

This macro releases the memory referenced by the pointer variable var.

void STREP (Tcl_Obj* o, char* s, int len)

This macro properly sets the string representation of the Tcl object o to a copy of the string s, expected to be of length len.

void STREP_DS (Tcl_Obj* o, Tcl_DString* ds)

This macro properly sets the string representation of the Tcl object o to a copy of the string held by the DString ds.

void STRDUP (varname, char* str)

This macro duplicates the string str into the heap and stores the result into the named char* variable var.

Assertions

void ASSERT (expression, char* message

This macro tests the expression and panics if it does not hold. The specified message is used as part of the panic. The message has to be a static string, it cannot be a variable.

void ASSERT_BOUNDS (int index, int size)

This macro ensures that the index is in the range 0 to size-1.

void STOPAFTER(n)

This macro throws a panic after it is called n times. Note, each separate instance of the macro has its own counter.

Tracing

All output is printed to stdout.

TRACE_ON
TRACE_OFF
TRACE_TAG_ON (identifier)
TRACE_TAG_OFF (identifier)

These "commands" are actually declarators, for use outside of functions. They (de)activate specific logical streams, named either explicitly by the user, or implicitly, refering to the current file.

For example:

    TRACE_TAG_ON (lexer_in);

All high- and low-level trace commands producing output have the controlling tag as an implicit argument. The scope management commands do not take tags.

void TRACE_FUNC
void TRACE_TAG_FUNC (tag)
void TRACE_FUNC_VOID
void TRACE_TAG_FUNC_VOID (tag)

Use these macros at the beginning of a C function to record entry into it. The name of the entered function is an implicit argument (__func__), forcing users to have a C99 compiler..

The tracer's runtime maintains a stack of active functions and expects that function return is signaled by either TRACE_RETURN, TRACE_RETURN_VOID, or the equivalent forms taking a tag.

void TRACE_RETURN_VOID
void TRACE_TAG_RETURN_VOID (tag)

Use these macros instead of

return

to return from a void function. Beyond returning from the function this also signals the same to the tracer's runtime, popping the last entered function from its stack of active functions.

any TRACE_RETURN ( char* format, any x)
any TRACE_TAG_RETURN (tag, char* format, any x)

Use this macro instead of

return x

to return from a non-void function. Beyond returning from the function with value x this also signals the same to the tracer's runtime, popping the last entered function from its stack of active functions. The format is expected to be a proper formatting string for printf and analogues, able to stringify x.

void TRACE ( char* format, ...)
void TRACE_TAG (tag, char* format, ...)

This macro is the trace facilities' equivalent of printf, printing arbitrary data under the control of the format.

The printed text is closed with a newline, and indented as per the stack of active functions.

void TRACE_HEADER (int indent)
void TRACE_TAG_HEADER (tag, int indent)

This is the low-level macro which prints the beginning of a trace line. This prefix consists of physical location (file name and line number), if available, indentation as per the stack of active scopes (if activated), and the name of the active scope.

void TRACE_CLOSER
void TRACE_TAG_CLOSER (tag)

This is the low-level macro which prints the end of a trace line.

void TRACE_ADD (const char* format, ...)
void TRACE_TAG_ADD (tag, const char* format, ...)

This is the low-level macro which adds formatted data to the line.

void TRACE_PUSH_SCOPE (const char* name)
void TRACE_PUSH_FUNC
void TRACE_PUSH_POP

These are the low-level macros for scope management. The first two forms push a new scope on the stack of active scopes, and the last forms pops the last scope pushed.

TRACE_TAG_VAR (tag)

Helper macro converting from a tag identifier to the name of the underlying status variable.

TRACE_RUN (code);

Conditionally insert the code at compile time when the tracing facility is activated.

TRACE_DO (code);
TRACE_TAG_DO (tag, code);

Insert the code at compile time when the tracing facility is activated, and execute the same when either the implicit tag for the file or the user-specified tag is active.

Authors

Andreas Kupries

Bugs, Ideas, Feedback

This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such at https://github.com/andreas-kupries/critcl. Please also report any ideas for enhancements you may have for either package and/or documentation.

Keywords

C code, Embedded C Code, code generator, compile & run, compiler, dynamic code generation, dynamic compilation, generate package, linker, on demand compilation, on-the-fly compilation

Category

Glueing/Embedded C code