shape - Online in the Cloud

PROGRAM:

NAME

shape - identify and build program configurations from versions of source objects

SYNOPSIS

shape
[ -f <description file> ]
[ -R <version selection rule> ] [ -V <variant name> ]
[ -echo <macro name> ] [ -force <target> ] [ -rebuild <target> ]
[ - dDehiknprs ]
[ -bct ] [ -help ] [ -nomsg ] [ -novclass ] [ -version ] [ -xpoff ] [ -xpon ]
[ target1 target2 ... ] [ macro=value ... ] [ macro+=value ... ]

DESCRIPTION

Shape allows to transparently compile source objects that are either regular files, or
source object versions in the ShapeTools version object base. More generally, shape
produces a set of derived objects (``targets'') from appropriately selected versions of
corresponding source objects according to a description of the dependencies between the
objects. Shape keeps track of the relevant parameters for compilations (source versions,
compiler versions, compiler switches etc.) and thus provides a safe and efficient build
machinery.

When shape compiles source objects, it stores the resulting derived objects together with
the effective compile parameters in its derived object cache. Before the derivation
process for a requested object is actually started, shape attempts to find an existing
derived object that matches the requirements for the target, in the derived object cache.
Caching and restoring of objects that are derived from immutable versions allows
developers to profit from previous builds by other team members. Overall compile costs in
projects are substantially reduced.

When serving a build request, shape considers a possibly large number of versions that are
stored for an object. Which particular version is bound to an object's name in the
description file, is determined by version selection rules.

Shape can manage builds of different variants of a system in parallel. Shape uses the
combined potential of dynamic version selection, dynamic macro redefinition, and derived
object management to handle variant builds. As most - if not all - of the objects and
parameters involved in a build are defined as macros, shape provides a great deal of
flexibility by allowing to alter some or all of the macros dynamically, depending on which
variant shall be built. The concept of variant definition in shape's description file
offers a clear focal point for all definitions that are relevant for a certain variant.

OPTIONS

-f <description file>
shape uses the supplied argument as name of the description file to be used for the
build. If no -f option is specified, shape tries to find a description file under
one of the names ``Shapefile'', ``shapefile'', ``Makefile'', and ``makefile'' (from
left to right). If no regular file with one of these names can be found, but
versions of respective files are available in the version object base, shape will
use the most recent version. When more than one -f <description file> argument
pair appears, shape reads each description file in turn. If the name of the
description file is specified as ``-'', shape will read the system description from
standard input. It is possible to specify the description file in bound version
notation, e.g. Shapefile[2.8] or Shapefile[Release4] (see vbind(1) for details
about bound version notation).

-R <selection rule name>
activates the specified selection rule as initial version binding for source
objects. If the -R option is present, and a selection rule is defined as the first
dependency of the first target, shape will use the selection rule passed via the
command line, and ignore the first (and only the first) selection rule activation
within the description file. The option is useful to override initial default
selection rules, specified within the description file, from the command line.

-V <variant name>
activates the variant specified by <variant name>. Several variants can be
activated simultaneously from the command line by specifying the -V option multiple
times. All variant specific definitions will be in effect as soon as shape reads
the corresponding variant definition in the description file.

-force <target>
forces shape to build the specified target unconditionally, i.e. even if a
suitable, previously build object exists.

-echo <macro name>
the value of the macro <macro name> is written to standard output. This option is
useful to extract information from the system description file (e.g. shape -echo
SOURCES, or shape -echo SUBSYSTEMS), or to control the effect of variant
activations.

-rebuild <target>
attempt a precise rebuild of target according to a bound configuration thread,
supplied in a file named <target>.bct (see description of -bct switch).

-d run shape in debug mode. Print out detailed information about object dependencies
and attributes.

-D print detailed information about the version binding process, and shape's reasoning
regarding (re)builds of targets, or retrievals from the derived object cache. This
switch is useful to find out about the exact reasons, why shape rederives a target
(or not).

-e macro definitions that are imported from the environment (see description of
special macro IMPORT, below) override macro definitions in the description file (by
default, macro definitions in the description file have precedence over imports
from the environment).

-h print usage information on standard output (this is an abbreviation for the -help
switch, see below).

-i ignore error codes returned by commands.

-k when a nonzero error status is returned by an invoked command, the work on the
current target is abandoned but shape continues with other branches that do not
depend on the failed target.

-n no execution mode. Shape prints out commands, but does not execute them. Even
command lines beginning with @ are printed. If a command contains the $(MAKE) macro
reference, however, that line is always executed in order to allow tracing of
recursive build processes.

-p print out the complete set of macro definitions, target descriptions, and rule
definitions, respectively.

-r do not use shape's built-in implicit rules. Implicit rules defined in the
description file remain in effect.

-s run in silent mode. Shape does not print out the commands before executing them.

-bct record the build in a bound configuration thread file. A shape configuration thread
contains precise definitions of all source versions, their dependencies, the
involved tools, and related options that were in effect for a build. The
configuration thread for a produced toplevel target (the first target in the
description file, or a target requested from the command line) is stored in a file
named <target>.bct. Bound configuration threads can be used as input for rebuilds
(see option -rebuild, above). If the source version context of a bct-build is
unsafe, shape will record that fact in the bct, and issue a warning message.

-help print usage information on standard output.

-nomsg turn off the trace facility msg in version selection rules.

-novclass
disable checking for incompatibility of activated variants.

-version
print the version identification of the shape program.

-xpoff turn off attribute expansion in source versions retrieved from the object base. By
default, attribute expansion is turned on for all source objects that are directly
retrieved from the object base, and turned off for source objects that are regular
files (see retrv(1) for details about attribute expansion).

-xpon turn on attribute expansion for all source objects, even in regular files. By
default, attribute expansion is turned off for source objects that are regular
files, and turned on for all source objects that are directly retrieved from the
object base.

target ...
A list of target names can be passed to shape via the command line. If no target is
given on the command line, and the special target .DEFAULT is not defined within
the description file, shape tries to produce the first target defined in the
description file.

<macro definition>
It is possible to define or modify macros in the description file from the command
line. Macros that are defined this way take precedence over all other definitions.
Command line macro definitions have either of two forms:

NAME=VALUE
and
NAME+=VALUE

with NAME being a word and VALUE an arbitrary string. If VALUE contains white space, make
sure to quote it. The first form of command line macro definitions sets NAME to the
substitution VALUE. If VALUE is empty, the macro is reset. The second form appends VALUE
with a leading space character to the current substitution of NAME. The current
substitution may be defined in the description file, or by a previous setting on the
command line. For details about the semantics of macro definitions and substitutions, see
the respective sections below.

DESCRIPTION FILES

The operation of shape is controlled by a system description file (usually a Makefile)
that provides structural information about the system to be managed. Other than make(1),
shape works on top of AtFS (Attributed File System), a repository of versioned objects,
rather than plain files. Thus, genuine shape description files (usually called Shapefile)
feature version selection rules, and variant definitions in addition to standard Makefile
dependency rules. Shape's description file is an upward compatible extension of make(1)'s
description file, the Makefile. A useful structuring convention for shape description
files is to maintain a Makefile, and a Shapefile in parallel. Only genuine shape
constructs (such as version selection rules, or variant definitions) are kept in
Shapefile, while the bulk of target rule- and macro definitions is kept in Makefile. The
Makefile shall be included in Shapefile (see description of include directive, below).
This structuring convention has the advantage that programs that were developed with the
support of the ShapeTools system can be shipped as source distribution to sites that don't
use ShapeTools.

Although shape is largely downward compatible with the original make program, it should be
noted that several popular extensions of the original make program, such as GNU Make or
Sun Make, provide features not present in shape. See the section on known
incompatibilities below.

The description file provides an ideal central information base for all sorts of product
related definitions. Shape encourages the development of a set of (project- or
organization-specific) conventions for system description, and provides a simple way to
extract this information for use by other tools (see -echo option, above). The description
file syntax not only serves to specify component dependencies that are relevant for build
processes, but allows a general, hierarchical definition of product oriented tasks. The
concept of recursive dependencies maps directly to a stepwise refinement of task
definitions. Such tasks can be fully, partly, or not at all automated as appropriate.
Thus, certain activities may be automated and standardized, while other activities are
just informally described in order to document them or to reason about them (see
shape_rms(1) for examples).

Syntactical Structure

The basic syntactical structure of shape's description file is made up of:

Comments
Comments begin with a ``#'' character and extend to the end of the line. In
Shapefiles, the end of a line is defined as an unescaped newline (``\<newline>''),
or the end of the file. The comment character can't be escaped, but can be quoted
in single- or double quotes. Comment characters in command lines of target rules
are ignored by shape.

Directives
Directives are special keywords, known to shape. Directives begin at column 0 of a
line and extend to the line end. Currently, the only directive recognized by shape
is

include <list of file names>

Macro Definitions
Macro definitions have the general form:

NAME <macro definition symbol> VALUE

NAME must be a single word consisting of a sequence of name characters. Name characters
are all printable characters except the following:

$ # : = ; <space> \t \n

The macro definition symbol is either of ``='', ``+='', or ``:=''. VALUE is an arbitrary
string terminated by the end of the line, or a comment. Macro definitions usually begin in
the first column of a line, but may be preceded by leading <space> characters. Macro
definitions must not contain leading <tab> characters (see section on Macro Definitions,
below, for more details).

Macro References
Macro references have one of the following forms:

$(<macro name>)
${<macro name>}
$<single character name>

The macro substitution operator (``$'') can't be escaped, but can be represented by the
substitution ``$$''. Macro substitution occurs anywhere in the description file, except in
comments, macro names, left hand sides of version selection rule- and variant definition
headers (see next section), and variant class definitions (see section on Macro
Substitutions, below, for more details).

Rules Rules are made up from a rule header, and an optional rule body. The rule header
consists of a left hand side, a rule definition symbol, and an optional right hand
side. The left hand side usually begins in column 0 of a line, and may be preceded
by leading <space> characters. Left hand sides of rule headers must not contain
leading <tab> characters. The optional right hand side of a rule header extends to
the end of the line, or the beginning of the rule body. A rule body consists of
consecutive lines beginning with a <tab> character. The body of a rule is
terminated by the next line not beginning with a <tab> character, or the end of the
file.

Shape recognizes three different kinds of rules, distinguished by their respective
rule definition symbols:

·
target rules. Target rules have a single colon character (``:'') as rule
definition symbol. The left hand side of target rule headers is a space-
separated list of names. The optional right hand side consists of a space-
separated list of names, followed by an optional list of production ingredients
(see section on Target Rules, below).

·
version selection rules. Version selection rules have the rule definition symbol
``:-''. The rule header of version selection rules has a single word on its left
hand side, and no right hand side (see section on Version Selection Rules,
below).

·
variant definitions. Although variant definitions are - as the name suggests -
definitions, not rules (from a semantical view point), their syntactical
representation is that of a rule. Variant definitions have the rule definition
symbol ``:+''. The rule header of a variant definition has a single word on its
left hand side, and no right hand side (see section on Variant Definitions,
below).

Variant Class Definitions
Variant class definitions have the form

vclass <name> ::= (variant1, variant2, ...)

(see section on Variants, below).

Line Continuations
If the end of an input line is escaped by a backslash (``\'') the next line is
considered as a continuation line. The backslash newline character sequence is
replaced by a space.

Macro Definitions

Macro definitions associate names with strings that will be substituted wherever the name
of the macro is referenced (see next section). Macros are useful for writing maintainable,
and somewhat generic description files. Even moderately large projects will find it
extremely rewarding to define conventions for naming and usage of certain macros
throughout the product description file.

There are three different kinds of macro definitions:

Simple Macro Definitions

A simple macro definition looks like

NAME = <any string>

The string that is associated with the macro name can contain macro references. If a macro
is defined multiple times within a description file, the last definition will be
effective. Macros defined on the command line take precedence over definitions of the same
macro in the description file.

Additive Macro Definitions

This type of macro definition looks like

NAME += <any string>

The string on the right hand side of the definition is appended to any existing value
associated with NAME, separated by a space character. Multiple additive macro definitions
are concatenated in the order in which they appear in the description file. If an additive
macro definition occurs on the command line, the last string value defined in the
description file is prepended to the string value defined on the command line. Additive
macro definitions in the description file are appended to string values defined on the
command line.

Evaluative Macro Definitions

Evaluative macros are defined in the following way:

NAME := <any string>

First, the string value is associated to NAME in the same way as for simple macro
definitions. When NAME is substituted for the first time, the right hand side of the
definition is evaluated, and the result of this evaluation replaces the original string
value associated with NAME. Thus, evaluation of the right hand side occurs exactly once.
This is particularly useful if the defining string is a command substitution (see next
section).

Macro Substitutions

Macro substitution is the process of substituting a macro reference by the string value
associated with a macro name. References to undefined macros are substituted by an empty
string. Macro references have either of the forms:

$(NAME)
${NAME}
$<any single character>

The following are valid macro references:

$(CFLAGS)
$7
${SOURCE-FILES}
$(X)
$X

The last two references have identical substitutions. The macro reference

$$

will substitute a single dollar sign.

Before a macro reference is substituted, the associated string will be evaluated.
Evaluation of a string value includes

-
substitution of all macro references in the string value

-
command substitution. Any substring of the string value enclosed in backquotes (```'')
will be passed as command to the shell, and be replaced by the command's standard
output.

-
string substitution. If a macro reference has the form

$(NAME:<old>=<new>)

the reference will be substituted by the evaluated value of NAME, with all occurrences of
the string <old> replaced by the string <new>. This is particularly useful to maintain
related lists, such as CSOURCES and OBJECTS for example, automatically:

CSOURCES := `echo *.c`
OBJECTS := $(CSOURCES:.c=.o)

Shape substitutes macro references as late as possible. Macro references occurring in a
macro definition are only substituted when the defined macro itself is substituted. Macro
references on the dependencies side of target rules are substituted when the rule is
evaluated. Macro references on the target side of target rules are substituted immediately
after shape has read the description file, i.e. before any production is started. Macro
references in include directives are substituted when the directive is executed while
shape reads the description file.

Built-in and Special Purpose Macros

In order to provide parametrization of shape's built-in implicit rules, a number of
predefined macros is supplied by convention. These macros have meaningful initial values
that can be altered by the user. There are also several macros that have special meaning
for shape.

Macro Purpose Initial value Remark

@ full name of the current <dynamic>special
target

? list of target dependencies <dynamic>special

< name of the first target <dynamic>special
dependency

* prefix shared by target <dynamic>special
and the dependent filenames

# bound version id of the current <dynamic>special
dependency

$ the character ``$'' $<special>

+ name of object to be bound <dynamic>special
to a version (selection rules
only!)

AS Program for doing assembly asconventional

ASFLAGS Flags for the assembler <none>conventional

CC Program for compiling C ccconventional
programs

CFLAGS Flags for the C compiler <none>conventional

FC Program for compiling Fortran f77conventional
programs

FFLAGS Flags for the Fortran compiler <none>conventional

HOSTTYPE Host architecture of the <none>special
computer that runs shape.
The value of this macro is
used by shape to construct
the derivation key attribute
for derived objects

IMPORT List of environment variables <none>special
that shall be imported as
macro definitions

LD Program to link programs ldconventional

LDFLAGS Flags for the linker <none>conventional

LEX Program to turn Lex grammars lexconventional
into C or Ratfor programs

LFLAGS Flags for the lexical analyzer <none>conventional
lex

LOGNAME The name or network-id under <dynamic>special
which the user who owns the
shape process is logged on

M2C Program for compiling Modula2 m2cconventional
programs

M2FLAGS Flags for the Modula2 compiler <none>conventional

MAKE The command line with which shape $(MAKEFLAGS)special
shape has been invoked.
This macro is used for
recursive calls to shape

MAKEFLAGS Command line flags relevant <defined fromspecial
for recursive calls to shape command line>

PC Program for compiling Pascal pcconventional
programs

PFLAGS Flags for the Pascal compiler <none>conventional

RFLAGS Flags for the Fortran compiler <none>conventional
for Ratfor programs

SHAPEPID The process id of the <dynamic>special
running shape program

SHAPEVERSION The version id of theshape_CM-4.4special
shape program (or above)

SHELL The command processor for /bin/shspecial
the target rule command
lines. The referenced command
processor must be able to
take its commands from
standard input (see section
on Command execution,
below)

VPATH Search path extension for <none>special
localizing source components

YACC Program to turn Yacc grammars yaccconventional
into C programs

YFLAGS Flags for yacc <none> conventional

vpath Dynamic search path extension <none>special
for variants of source components

The function of the special purpose macros HOSTTYPE, IMPORT, MAKE, VPATH, and vpath are
described in the sections on OPERATION, and Variants below.

Target Rules

A target rule defines how, and under what conditions a target is derived from a set of
source objects and/or other targets. A target is a name that can refer to a file but need
not to do so. Target rules have the following format:

<target>... : [<version binding>] [+<variant>...] [<dependency>...] \
[: <ingredient>...] [; <command>]
\t[<command>]
...

The header of a target rule (see Syntactical Structure, above) consists of a list of
targets, terminated by a colon, followed by an optional list of dependencies, and an
optional list of production ingredients, beginning after a second colon character. The
rule header is terminated by a newline or a semicolon, and followed by the optional rule
body. The rule body consists of command lines that are executed when a target needs to be
rederived. The first command line may immediately follow the semicolon that terminates
the rule header. Subsequent command lines must begin with a <tab> character. The target
rule body is terminated by the first line that doesn't begin with a <tab>, or by the end
of the file.

Targets

When multiple targets appear on the left hand side of a rule header, and the derivation
process needs to be started, shape will derive all of the targets in a single run.

Dependencies

Shape checks a target's dependencies from left to right. The first dependency is examined
whether it is the name of a version selection rule. If it is, shape sets the selection
rule active (eclipsing all previous selection rule activations), and proceeds to the next
dependency. Next, shape checks whether the dependency is a variant activation. If the
dependency starts with a ``+'' character followed by the name of a variant, the variant is
activated (see the section on Variants, below). Shape proceeds to check for variant
activations until the first dependency that isn't a variant activation is found. Next,
shape proceeds through the list of remaining dependencies, and binds (or derives) each of
them as necessary, performing a depth first traversal of the dependency graph (see the
section on OPERATION, below).

Production Ingredients

After all dependencies have been bound, shape constructs the derivation key for the
target. The derivation key is an attribute that defines the complete set of parameters
that determine whether a target needs to be rebuild. Besides all bound dependencies, the
derivation key contains the production ingredients that were specified in the target rule
header. Production ingredients are typically complete definitions of the macros that are
referenced in the command lines of the rule's body. Thus, tool versions and switches
affecting the operation of a tool can be made part of the derivation parameters of a
target. In order to include macro definitions into the derivation key of a target, the
special reference

+(NAME1) +(NAME2) ...

must occur in place of the production ingredients.

Command Lines

When shape concludes that a target needs to be (re-)derived, the commands in the target
rule body are executed. The rule body consists of consecutive lines that are treated as
separate commands. Each command line is evaluated as described in the section on Macro
Substitution, above, and passed to the command interpreter defined by the macro SHELL.
Each command line is executed as a separate process. If complex commands are needed that
don't fit on a single line, or if the overhead of repeated process invocations shall be
avoided, a logical command line can be extended by escaping the newline with a backslash
character (\<newline>), and continuing it on the next physical line.

Command lines may be preceded by one or two special characters:

- shape ignores any nonzero error code returned by a command line for which the first
character is a minus sign. The minus sign is not passed to the shell. When a
command returns a nonzero return status, shape usually considers the derivation
process for the target as failure and terminates, unless the -i or -k switches, or
the .IGNORE special target is in effect.

@ If the first character of a command is a ``@'', shape does not print the command
before executing it. The ``@'' is not passed to the shell.

@- If the first two non-<tab> characters are ``@-'', shape ignores nonzero return
codes, and suppresses the printing of the command line.

If shape is invoked in no execution mode (-n), the evaluated command lines are printed on
standard output, showing what shape would do if invoked without -n. Command lines that
contain the macro reference $(MAKE) are always executed, even if -n is set. This is done
to allow simulation of recursive builds that may span over subdirectories. The reference
$(MAKE) is substituted by a shape command invocation with all relevant command line
switches set.

Within command lines of the rule body, some parts of the target rule header can be
dynamically referenced. When a command line is evaluated, the following substitutions are
possible

Reference Substitution
$@ full name of the current target
$? list of dependencies
$< name of the first dependency
$* prefix shared by current and the dependent filenames
$# bound version id of the current dependency
(implicit rules only)

Implicit Rules

Shape's target rules come in two different flavors: explicit, and implicit. Implicit rules
can be seen as templates that define dependency patterns which apply to most targets of a
given kind. For this reason, implicit rules are sometimes called pattern rules. Shape
converts make's old-style implicit rules (e.g. .c.o:) to pattern rules while it reads the
description file. A typical dependency pattern is, for example, the dependency of files
containing linkable object code, e.g. module.o to corresponding files containing source
code, e.g. module.c. The derivation process for most of these source/derived pairs is
identical. Rather than writing separate rules for all source/derived dependencies of a
system, it is possible to write a single, generic rule, called implicit rule. An implicit
rule has the following format:

%[.<suff1>] %[.<suff2>] ... : %[.<suff3>] %[.<suff4>]... \
[: <ingredient>...] [; <command>]
\t[<command>]
\t[<command>]
...

While the structure of implicit rules is the same as described above, the names of targets
and dependencies are replaced by target patterns, and dependency templates respectively.
The percent character in a target pattern acts as wildcard that is matched against all of
a target's name up to the optional trailing suffix. For shape, an object name suffix is
the sequence of characters enclosed by the last period character (``.'') within the name,
and the <space> character terminating the name. The following example illustrates shape's
concept of suffixes:

Name Suffix
sample.cde cde
sample.x.y.cc
sample_c
.sample.c c

The following is an example for an implicit rule that derives linkable object code from
corresponding C source files:

%.o : %.c : +(CC) +(CFLAGS)
\t@echo shape - executing: $(CC) -c $(CFLAGS) $#;
\t@$(CC) $(CFLAGS) -E %.c |
sed 's;^\(# [0-9][0-9]* \"\)%.c\(\".*\)$$;e1$#\2;' > %.i;
\t@$(CC) -c $(CFLAGS) %.i;
\t@rm %.i;

NOTE: This rule is shape's built-in implicit rule to compile C source files. The cryptic
command sequence has the purpose to encode the complete file version id into the object
code (e.g. sample.c[3.4] rather than sample.c). This is extremely useful in conjunction
with with the -g switch of most C compilers, and version sensitive debuggers, such as
vgdb.

If a target is derived using implicit rules, the name of the target is matched against the
target patterns of the implicit rules. If a rule matches, the matching portion of the
target name (the stem, referred to by the ``%'') is consistently substituted for all other
occurrences of the wildcard character throughout the rule. Once this is done, the implicit
rule is treated like an explicit target rule.

Explicit Rules

Explicit rules associate explicit target names with explicit dependencies. Explicit rules
are most typically used to specify dependencies that cannot be covered by implicit rules,
such as deriving an executable program by linking many object code modules. In many
cases, explicit rules are used to specify only those target dependencies that are not
implied by an implicit rule (such as include dependencies for object files), while the
``natural'' dependencies are assumed as being present. If a description file contains only
this sort of explicit dependencies, the omitted implicit dependencies (and an applicable
rule body) are automatically added by shape to the total list of target dependencies.

Built-in Implicit Rules

Shape provides a number of predefined implicit target rules that cover many common
source/target derivations. The following table lists target patterns, and dependency
templates for shape's built-in implicit rules.

Target Dependency Derivation
%.a %.c Compile archive library from C source
%.c %.l Generate C programs from Lex grammar
%.c %.y Generate C programs from Yacc grammar
%.o %.l Compile object code from Lex grammar
%.o %.y Compile object code from Yacc grammar
%.o %.s Translate assembler program to object code
%.o %.r Compile Ratfor source
%.o %.F Compile Fortran source
%.o %.f Compile Fortran source
%.sym %.def Compile Modula definition modules
%.o %.mod Compile Modula implementation modules
%.o %.p Compile Pascal source
%.o %.c Compile C source
% %.sh Make executable program from shell-script
% %.r Build executable program from Ratfor source
% %.F Build executable program from Fortran source
% %.f Build executable program from Fortran source
% %.p Build executable program from Pascal source
% %.mod Build executable program from Modula source
% %.c Build executable program from C source

For a complete definition of shape's built-in implicit rules, run shape -p.

Special Purpose Targets

Several aspects of shape's operation are controlled by special purpose targets that can be
put into the description file. Special purpose targets by convention begin with a period
character, and have no associated commands.

Target Purpose

.DEFAULT: commands in the rule body of the .DEFAULT target rule are executed for all
targets that cannot be derived by explicit or implicit target rules. If no
commands at all shall be executed for a rule but .DEFAULT is needed for other
targets, that rule can be given an empty command (either a ``;'' at the end of
the rule header, or an empty line beginning with <tab>). If .DEFAULT has
dependencies, and no targets are requested from the command line, these
dependencies are treated as if they were targets requested from the command
line.

.IGNORE: causes shape to ignore non zero return codes of invoked commands. Equivalent
to the -i switch

.SILENT: silent command execution. The command lines are not printed before execution.
Equivalent to the -s switch

.BPOOL: only the dependencies associated with this target are stored in the derived
object cache

.NOBPOOL: dependencies associated with this target are not stored in the derived object
cache.

If both, .BPOOL, and .NOBPOOL are defined, only the difference set of both dependency
lists will be stored in the derived object cache.

Version Selection Rules

When shape builds a target, it uses version selection rules to bind a unique version to
each name of the prerequisite source objects. Version selection rules consist of a name,
and an associated set of predicate lists in the rule body. The format of version selection
rules is:
<name> [( <arg1>, <arg2>,...)] :-
\t[<pattern1>,] <pred1> (...), <pred2> (...);
\t[<pattern2>,] <pred1> (...), <pred2> (...);
...
\t.
The body of a version selection rule consists of a sequence of alternatives, separated by
semicolons. Each of the alternatives is an optional pattern, followed by a comma-separated
list of predicates. The selection rule is terminated by a period character. The semicolon-
separated sequence of alternatives in a version selection rule constitutes a logical OR
expression. The comma-separated list of predicates in an alternative constitutes a logical
AND expression.

Version Binding

Version binding is the process of determining exactly one version of a given source object
from the set of all available versions. Version binding is said to succeed if one of the
rule alternatives succeeds. An alternative succeeds, if it leads to the identification of
exactly one version. It is said to fail otherwise. When shape binds a version to the name
of a source object, it tries each alternative with a matching pattern, until the name is
unambiguously bound to a version. If the pattern is omitted, the alternative will be tried
unconditionally.

The functioning of version selection rules is one of shape's most important, yet most
subtile aspects. In order to provide a basis for an intuitive understanding of the
selection rule mechanism, an example is described. The rule most_recent, below, binds:
- files that were checked out for modification by the shape-invoking user
- versions of files that were recently modified (→ status saved) by the same user
- the most recently proposed version (→ status proposed) of files modified by other users,
- or the file version from the last release.

LASTRELEASE := `lastrelease`# "lastrelease" returns the name
# of the last release
most_recent :-
eq (status, busy), exists ($+[locked_by($(LOGNAME)):]);
ge (status, saved), max (mtime),
max (version), eq (author, $(LOGNAME));
ge (status, proposed), max (mtime),
max (version);
eq (__SymbolicName__, $(LASTRELEASE));
cut ($_rule$: couldn't bind $+ as requested!).

locked_by (user_id) :-
max (version), eq (locker, $_user_id$).

For a more detailed description of version selection rule syntax, semantics, and the list
of built-in predicates, see BindRules(7).

Activation of Version Selection Rules

A version selection for a certain target is invoked by specifying the name of the
selection rule as first dependency of a target, or by supplying a selection rule name as
argument to the -R option. If no selection rule is specified explicitly, shape uses its
built-in version selection rule that tries to bind a regular file, or the most recent
version to the name of an object.

Variants

The term variant refers to the intention to manage a product that must comply with
different sets of varying external constraints as a unit. Independently from particular
semantics that might be associated with the variant notion, there exists a small number of
techniques to implement software variation on a technical level. These techniques are:

physical separation of variant components. This is achieved by maintaining separate copies
of components in different directories, or by maintaining variant specific branches in
version control systems;

source preprocessing of variant components. With this technique, multiple logical variants
of a source component are maintained in a single file that contains preprocessor
instructions. Before a particular variant can be accessed, a preprocessor must extract it
from the common source. A popular example of this technique is conditional compilation,
controlled by the #if, and #ifdef instructions within the domain of C/C++ programming;

composition variation of complex product variants. This technique addresses the case when
different variants of a complex product (such as a program) are composed from different
sets of components;

derivation variation (or variation of the process) that produces different variants of
derived objects from the same set of sources by modifying parameters of the derivation
process. A typical example for this case is cross compilation of the same sources for
different target platforms, or code instrumentation for various purposes, such as
debugging, testing, profiling, or optimization.

Depending on the particular needs of a project, all of these techniques may be in
simultaneous use, and can occur intermixed as appropriate. Shape allows to associate
logical variant names with a set of definitions that control all of the above mentioned
techniques, making it possible to request builds of particular system variants (and
combinations of compatible variants) without the need to worry about how these variants
are realized technically.

Variant Definitions

Shape derives its flexibility from using macro substitution in the description file
wherever possible. Shape variant definitions are basically groups of macro definitions
that take effect when the variant is activated for a build. A variant definition has the
following format:

<variant-name> :+
\t<Macro name1>=<Value>
...

When a variant is activated, the macro definitions associated with the variant become
effective. Any previous definition of a macro made in the description file, or on the
command line is replaced by the variant macro substitution. If a macro is defined in
several variants that are activated together, the respective values are concatenated.

Locating physically separate Variant Source Objects

Shape provides a special macro, vpath, that is intended to be used in variant definitions.
The vpath macro defines shape's search precedence when source version archives are
located. If vpath is non-empty, shape tries to find any referenced source object in the
vpath directories first. If several activated variants define vpath, the variant search
path is concatenated and searched from right to left, i.e. the last variant that has been
activated has precedence. Only if a referenced source component cannot be found in any of
the vpath directories, the current directory is searched. If a source object has been
found, it will be bound by the current version selection rule, and be temporarily
installed in the build directory. This means that components which are maintained in a
vpath subdirectory are temporarily moved up to the main directory. Thus, it is not
necessary to make any reference to a vpath subdirectory path in the target rules.

Variant Activation

When a product is configured and built, variants are typically activated by supplying a
variant name as argument to the -V options.

Variants can also be activated for a given target by specifying respective, ``+''-prefixed
variant names as dependencies (see section on Target Rules, above). Variant activations
for a target must occur before any real object dependency on the dependency line, and
after the optional version selection rule activation.

Variant Class Definitions

With Variant class definitions, shape offers a construct that allows to define
incompatible variants, i.e. variants that cannot be activated simultaneously. Shape
variant class definitions have the following format:

vclass <variant-class-name> ::= ( <var1>, <var2> ...)

The same variant name can occur in multiple variant class definitions. If a combination
of variants is requested with any two variant names that are member of the same variant
class, shape will issue an error message, and terminate. Checking of variant classes can
be disabled by specifying the -novclass switch on the command line.

NOTE: variant class definitions must occur in the description file before any variant
definition referenced in a variant class. Variant classes that are defined after
referenced variants cannot enforce mutual exclusion of incompatible variants.

An Example

The following example shall illustrate the use of variant definitions, and variant
classes:

vclass compiler ::= (gnu, prop)

gnu:+
CC = gcc -Wall
OPTIMIZE = -O2 -inline-functions
DEBUG = -g -g3
PROFILE = -pg -a
STDC = -ansi

prop:+
CC = cc
OPTIMIZE = +O3
DEBUG = -g -z +Y
PROFILE = -G
STDC = -Aa

vclass quality ::= (debug, profile, optimize)

debug:+
VARCFLAGS = $(DEBUG)

profile:+
VARCFLAGS = $(PROFILE)

optimize:+
VARCFLAGS = $(OPTIMIZE)

CFLAGS += $(VARCFLAGS)

If a variant requires the modification of macros with predefined meaning, it is sometimes
a good idea not to redefine the macro itself in the variant section. In such a case it is
possible to augment an existing macro value by using shape's additive macro definition
facility, and a macro from the variant definition defined for this purpose (e.g. VARCFLAGS
in the example above).

OPERATION

When invoked, shape first parses the command line. Shape records the names of the variants
to be activated from the command line via the -V option. Next, shape initializes the
built-in, and special macros. Also, shape's built-in derivation rules are initialized.

Reading the Description File

After that, all macro definitions made on the command line are made effective. Shape then
locates and opens its description file. If no description file is specified as argument to
the -f option, shape tries to find one of the files Shapefile, shapefile, Makefile, or
makefile. For each of these names, shape tries to find a regular file first, and, if no
such file exists, to find the most recent version of that file in a version control
archive. If no such version can be found, shape tries the next name.

When shape reads the description file, it collects all macro definitions, and makes them
immediately effective, unless a macro of the same name has been defined on the command
line. If the special macro IMPORT is encountered, the listed environment variables are
defined as macros. If macros with the same name as an imported environment variable occurs
in the description file, it has precedence over the definition from the environment,
unless the -e switch is in effect.

When shape reads an include directive, it evaluates the rest of the line (i.e. the
characters that immediately follow the directive), and interprets each word as the name of
a file to be read. Each of the file names is bound to either a regular file, or the most
recent version of the file. Shape opens each of the included files, suspends reading the
current description file, and continues to read the contents of the included file(s),
before it resumes reading of the original control file. If multiple file names are
specified in an include directive, shape reads each of the files in turn, starting with
the leftmost, and ending with the rightmost file name. If an included file could not be
opened, shape issues a warning.

While shape reads its description files, version selection rules, and target rules are
collected. They are defined only after shape has finished reading the description file.
Macro-, variant-, and variant class definitions are made effective as soon as they have
been recognized.

The Build Process

After the description file has been read, shape determines which targets have been
requested. If targets have been requested from the command line, shape will attempt to
build each of them, starting with the leftmost target and proceeding towards the
rightmost. If no target has been requested from the command line, shape searches the
description file for a target named .DEFAULT. If such a target exists, and there are any
dependencies associated with it, shape will attempt to build each of these dependencies,
from left to right. If no .DEFAULT target rule has been defined in the description file,
shape will attempt to build the first target defined in the description file.

When shape builds a target, it proceeds as follows:

1)
determine the names of the source objects for a given target by traversing the
dependency graph, using built-in and user supplied target rules. The dependency graph
is traversed depth first. The ids of all applied rules are recorded.

2)
for each required source object, locate the source version archive in the repository.
Locating of source version archives takes the current vpath into account.

3)
bind each of the source object's names to an appropriate version as implied by the
currently active version selection rule. Record the id of each bound dependency. If a
dependency is itself a derived object, use its cache key as id.

4)
construct the derivation key for the current target from the target name and the
records resulting from steps 1) and 3).

5)
search the derived object cache for an object that has a derivation key identical to
the key constructed in step 4).

6a)
if an appropriate derived object was found, a copy of it is installed in the build
directory, rather than deriving it from its sources.

6b)
if no appropriate derived object was found, it is created by deriving it from its
parts. The resulting derived object is put into the derived object cache, and
associated with the derivation key resulting from step 4).

Targets with an empty list of dependencies - and thus an empty derivation key - are always
(re-) derived.

When shape determines the dependencies of a requested target, it does so by evaluating
either explicit target rules, or by applying - possibly built-in - implicit rules. If
explicit target rules specify object dependencies but no derivation script in the rule
body, shape will attempt to supply an appropriate default derivation script. When
searching for such a default derivation script, shape tries to find an applicable implicit
rule for the current target. An implicit rule is considered applicable, if it has the
current target in its list of targets (after pattern substitution), and all - explicit,
and implied - dependencies exist. If no implicit rule is found to be applicable, shape
looks for the .DEFAULT target rule. If such a rule exists, and if it has an associated
derivation script in its rule body, this script will be supplied as default derivation
script. If neither of the two possibilities leads to a default derivation script, shape
gives up.

Derived Object Caching

Before the derivation process for a requested target is started, it is attempted to find a
suitable derived object in the derived object cache that matches the required properties.
Shape is based on the derivation key concept for target objects. The derivation key is
constructed according to the algorithm described above. Relevant parameters that go into
the derivation key are the list of dependency ids, the target rule id, the list of
production ingredients, the build platform (usually defined by the macro HOSTTYPE; if this
macro is not defined, shape takes the host id as build platform), and the attribute
expansion status of each source object. When an object has been derived, shape stores it
in the derived object cache, and marks it with the derivation key attribute. For a
detailed trace of shape's derived object cache handling, and the use of derivation keys,
run shape with the -D switch.

Command Execution

When a target needs to be (re-) derived, shape executes the commands associated with the
target. Before the commands are executed, shape sets up the command execution context. The
version objects of the target's dependencies are installed as regular files in the file
system. If necessary, shape retrieves source objects from the version control archive. If
a file with the object's name already exists in the place where a version is to be
installed, shape will temporarily move it to the AtFS subdirectory. After the command
script has completed, shape will restore the original state of all affected directories.

Shape executes a command line by starting the program referenced in the $(SHELL) macro,
and opening a pipe to the resulting process. The command line is written to the pipe, and
thus sent to the $(SHELL) process' standard input.

Each of the command lines in a rule body are executed by a separate process. Thus, the
execution status of separate commands is not preserved. If multiple commands are needed
that rely on the execution status of previous commands, all these commands must occur in a
single command line. This is possible with line continuations (see section on Syntactical
Structure, above).
NOTE: many command interpreters use the ``$'' character as special symbol (typically as
variable reference). Make sure to pass ``$'' characters in commands to the $(SHELL)
process by using the ``$$'' special macro (see section on Macro References, above).

INCOMPATIBILITIES

In order to facilitate migration from make(1), shape was designed to be upward compatible
with Makefiles. Although most of make's description file features are present in shape,
there is a number of incompatibilities that may need to be taken care of. There exists
also a number of popular extensions of the original make program (e.g. Sun's Make, HP's
Make, GNU Make, nmake etc.) that offer various special features that aren't supported by
other make extensions, or by shape. When a migration from make to shape is planned, it
should be checked whether special extensions or incompatible features are used.

Features not supported by shape

Double colon rules
Double colon rules associate the same target with different derivation scripts.
This type of rule is useful to support different derivations for a target depending
on which dependencies are out of date. Because shape bases its decision whether to
derive on the derivation key, rather than mere modification time stamps of files,
this sort of rule makes no sense in shape.

Archive member targets
Archive member targets are objects that live in an archive file (see ar(1)) rather
than the file system. Within these archives, make bases its decisions on the
modification time stamps of source files, and archive entry dates. There is no way
for shape to simulate the concept of derivation keys for archive members.
Maintenance of archives, however, is easy with shape, because all data for compiled
object files is maintained in the derived object cache. If the source for an object
that is stored in an archive is modified, shape can rederive this object, and
selectively replace the entry in the archive.

SCCS stuff
In order to provide basic support for team oriented development processes, make
allows to retrieve the most recent version of source files from SCCS archives.
Because of the awkward naming convention for SCCS version archive files, special
support for dealing with these archives had to be built into make. Because shape is
tightly integrated with the AtFS version object repository, there is no need for
any special SCCS support.

Special targets
Shape does not recognize the special targets .PRECIOUS:, and .SUFFIXES:. The
.PRECIOUS target in Makefiles has the purpose to prevent deletion of expensively
derived intermediate targets (by default, make deletes intermediate targets).
Because shape stores intermediate targets in the derived object cache, there is no
need for the .PRECIOUS feature. To prevent caching of possibly large, useless
intermediate targets, use the .NOBPOOL: special target (see section on Special
Targets, above). The .SUFFIXES target in Makefiles has the purpose to introduce new
suffix types into make's derivation engine, and to determine the order in which
implicit rules (suffix rules in make terminology) are applied. In shape, new suffix
types can be added dynamically, simply by introducing new implicit rules. Moreover,
shape has an intelligent algorithm the determines the applicable implicit rule.

Features with different semantics

Environment Variables
Many make programs import the entire set of environment variables as macro
definitions into the build process. This can sometimes produce surprising results.
In shape, environment variables are explicitly imported with the IMPORT special
macro.

? Macro
In make's target rules, the special macro reference $? is substituted by the names
of those dependency file names that have been updated since the current target has
been derived. Because shape bases its decision whether to derive on the concept of
derivation key, rather than mere file modification time stamps, the ? macro cannot
be correctly defined. Instead, shape substitutes the entire list of dependency
names - updated or not.

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