Copyright © 2015 Curt Hill Make An Indispensable Developer’s Tool.

Copyright © 2015 Curt Hill

MakeAn Indispensable Developer’s

Tool

Introduction• Make is the name of a “scripting

language” interpreter – Designed specifically for compiling and

linking a programming project

• Originally a UNIX program• Has escaped the UNIX ecosystem and

is now everywhere• Refers to any of a set of programs that

do approximately the same thing• Every IDE either uses an existing

make or has a custom one


Components• There are typically two

– The program itself– The script file that describes the

executable build process• This often has the name make or makefile• With or without an extension


Process• Making a project is a matter of

checking dependencies and dates• A dependency exists when one file

depends upon another• Thus the executable usually depends

upon object files– Object files depend upon source files

• If an item is older than what it depends upon it must be rebuilt


Example• Suppose x.exe depends upon x.obj,

date.obj and classy.obj• When make is executed it finds that

x.exe is newer than data.obj and x.obj but older than classy.obj

• It now knows that it must re-link x.exe so as to incorporate the new class.obj

• It does the same process for obj files that depend on source files– Thus it only compiles and/or links what is out

of date


Statement Types• Comments – not really a statement• Assignments• Directives• Implicit rules• Explicit rules


Syntax• Comments are indicated by an

octothorp (#)– These are ignored– Standard UNIX scripting practice

• Assignment statement has a mostly standard format– Variable = expression– The expression does not necessarily

look like a C style expression– Often files separated by blanks


Explicit Rules• General form is two linestarget: dependencies[tab] system commands

• Targets are typically executables or object files– Other things possible

• The dependencies are one or more files that the target needs to be built

• The command is how to accomplish it


Explicit Rules Again• The usual form is target as a file:xyz.o: xyz.cpp classy.h [tab] gcc –c xyz.cpp

• If either classy.h or xyz.cpp is newer than xyz.o or if xyz.o does not exist then gcc with the c option is run on xyz.cpp


Target • Usually the target is a file like that

previously shown• Does not have to be a real file• We could do something like:all: xyz.cpp classy.cpp[tab]gcc xyz.cpp classy.cpp

• The normal execution of gcc will produce xyz.exe not all or all.exe


The $ • The $ function is an inclusion of variable’s

value• Form: $(variable)• Thus if we have:CPP = g++.exe

• Then we later see:$(CPP) -c ggapp.cpp

• This becomes the command line:g++.exe -c ggapp.cpp

• We can now easily change compilers or set options


Example:• This is from a DevC++ make file• Create ggFrm.oObjects/MingW/ggFrm.o: $(GLOBALDEPS)

ggFrm.cpp ggFrm.h date.h

$(CPP) -c ggFrm.cpp –o Objects/MingW/ggFrm.o $(CXXFLAGS)


Implicit Rules• Also known as inference rules• This keeps us from explicitly specifying

all the rules explicitly• Usually involve a wildcard character %• Consider the following implicit rule:

%.obj : %.cpp[tab] $(CPP) –c $(.SOURCE)

• This says: whenever you need an object file, such as x.obj, then do a gcc –c x.cpp


Directives• If statements that allow some

alternatives• The keywords are if, else, elif, endif

– Sometimes these are prefixed by a % or ! in various derivatives

• This allows us to parameterize a makefile


Example:if $(CC) == bcc LDFLAGS = /Lf:\bc\lib

elif $(CC) == cl LDFLAGS = /Lf:\c6\lib; else

abort endif


Languages• Do not be confused, the C family is not

the only language processing that can occur

• Many C/C++ projects have one or more subroutines in assembly– FORTRAN numerical routines are also

common

• Most GUIs in Windows have a source file, often a .rc, that compiles into a .res file – Wxforms compile eventually into .res


DevC++• Uses a rather normal UNIX style

make• The script is in:

makefile.win– Even in a console program

• Program itself is:…\MinGW32\bin\mingw32-make.exe

• The project file is not the make file– It looks like a UNIX initialization file


Alternatives• There is no compelling reason why a

system has to follow the UNIX pattern for a make file

• Eclipse merely compiles all Java files in the projects directory

• Visual Studio has a proprietary (and hidden) make process

• Borland/CodeGear/Embarcadero used a variant of UNIX make up through version 6 and then switched to an XML format


References• Here are some web references for

more information:• http://mrbook.org/blog/tutorials/make/• http://www.cs.colby.edu/maxwell/

courses/tutorials/maketutor/• http://www.cs.swarthmore.edu/

~newhall/unixhelp/howto_makefiles.html

• http://www.opussoftware.com/tutorial/TutMakefile.htm


Finally• We should browse through a make

file or two• Inher_demo has several classes

including an inheritance hierarchy• Projects\p2c\src\make is a standard

UNIX make


Copyright © 2015 Curt Hill Make An Indispensable Developer’s Tool.

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