GNU make. Michal Koutný. Software development and monitoring tools (NSWI126)

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1 GNU make Michal Koutný Software development and monitoring tools (NSWI126)

2 Make basics Dependency tree (target and prerequisites) Check prerequisites, build target with recipe Configured via Makefile (a textfile) target prerequisites recipe results.tex: results.csv iconv -f latin2 -t utf8 $< \ cut -d\; -f1,2,3,4,5,6,7,8,9,10,12,13,14 \ sed '/^$$/d;/^%/d;s/;;/;--;/g;s/;;/;--;/g;s/;/ \& /g;s/$$/\\\\/' \ sed -e '2i\\\\midrule' > $@ TAB!.RECIPEPREFIX variable Shell command $(SHELL) variable

3 Makefile content Explicit rules (mentioned previously) Implicit rules More generic Variable definitions Configuration, macros, readability Directives configuration Comments Documentation, readability

4 Implicit rules (pattern rules) Pattern rules %.dvi: %.tex tex $< Only one % Chaining of implicit rules %.pdf: %.dvi dvipdfm $< Intermediate files are removed unless listed in.secondary or.precious prerequisites. Static pattern rules Apply only to specified targets final.pdf draft.pdf: %.pdf: %.dvi dvipdfm $<

5 Implicit rules (predefined) C programs %.o: %.c $(CC) $(CPPFLAGS) $(CFLAGS) -c C++ programs %.o: %.cc # also.cpp or.c $(CXX) $(CPPFLAGS) $(CXXFLAGS) -c assembler %.o: %.s $(AS) $(ASFLAGS) %.s: %.S # preprocessing $(CPP) $(CPPFLAGS) linking %: %.o $(CC) $(LDFLAGS) n.o $(LOADLIBES) $(LDLIBS) other Yacc, Lex, Fortran

6 Specialties Ignore errors In recipe -rm -rf *.o Globally with option -i Suppress echoing In 'Show once.' Globally with option -s

7 Phony targets Targets that represent no real file Used for naming actions (clean) Performance optimization Ultimate solution for recursive make Error handling Dependencies Parallel builds SUBDIRS = foo bar baz subdirs: for dir in $(SUBDIRS); do \ $(MAKE) -C $$dir; \ done SUBDIRS = foo bar baz.phony: subdirs $(SUBDIRS) subdirs: $(SUBDIRS) $(SUBDIRS): $(MAKE) -C $@ foo: baz

8 Common (phony) targets (goals) all Make all the top-level targets the makefile knows about. Usually first specified target => default target clean Delete all files that are normally created by running make. distclean Usually delete more files than clean does. For example, this would delete configuration files or links that you would normally create as preparation for compilation, even if the makefile itself cannot create these files. install Copy the executable file into a directory that users typically search for commands; copy any auxiliary files that the executable uses into the directories where it will look for them. uninstall target as inverse for install (however, not always supported) check, test Perform self tests on the program this makefile builds.

9 Variables Make supports simple text preprocessing. Setting variables (decreasing precedence) From the environment (only exception SHELL) Inside Makefile On CLI override inside Makefile override foo=new value Flavors of variables foo=world Recursively expanded bar=$(foo) Simply expanded baz:=$(foo) foo=hello echo $(bar) $(baz)

10 Text manipulation Substitutions At the end of a word (ignoring trailing whitespace) foo=bar.a baz=$(var:a=b) # baz == bar.b Appending ( two flavors of operator +=) Internally foo = first $(param) temp = first $(param) foo += second foo = $(temp) second# param will be expanded after use of foo foo = $(Foo) second# recursion foo := first $(param) # param must be defined when using += foo += second Text (and filename) functions $(function argument[, argument[,argument...]]) $(subst ping,pong,ping pong) pong pong $(patsubst.%,%,.hidden.hidden visible) hidden hidden visible $(dir somewhere/file local) somewhere./ (complementary notdir) $(suffix file.ext file.foo) ext foo (complementary basename) $(addsuffix.o, foo bar) foo.o bar.o (also addprefix) $(wildcard *.c *.p?f) foo.c file.pdf (use in non-expanding contexts) Wildcard expansion in targets, prerequisites automatically made by make. In recipes wildcard expansion made by shell. $(filter %.c %.s,foo.c bar.c baz.s ugh.h) foo.c bar.c baz.s

11 Automatic variables Useful variables whose value depends on context. The file name of the target of the rule. $< The name of the first prerequisite. $^ The names of all the prerequisites, with spaces between them. $* The stem with which an implicit rule matches (%). The directory part of the file name of the target (semiobsolete $(dir The file-within-directory part of the file name of the target. $(.D) or $(.F) variants of other aforementioned variables also exist.

12 Implicit rules variables Variable Default Meaning AS as Assembler CC cc C compiler CXX g++ C++ compiler CPP $(CC) -E C preprocessor YACC yacc Parser generator LEX lex Lexical analyzer generator RM rm -f Command to remove file CFLAGS Flags for C compiler CXXFLAGS Flags for C++ compiler CPPFLAGS Flags for C preprocessor LDFLAGS Flags for linker

13 Generating prerequisites Problem: code development introduces new dependencies Makefile obsoletes. C compiler's option -M, read #include directives and output in Makefile format # create dependency file %.d: -e; rm -f $@; \ $(CC) -M $(CPPFLAGS) $< > $@.$$$$; \ sed 's,$$*$\.o[ :]*,\1.o $@ :,g' < $@.$$$$ > $@; \ rm -f $@.$$$$ sources = foo.c bar.c # include causes.d files be remade when necessary include $(sources:.c=.d) LaTeX Makefile ( Automatically generates prerequisites via sed extraction.

14 Extras Parallel execution -j N Number of slots, i.e. parallel processes run Consequences: Interleaved output Unavailable stdin (not accessible for more processes) In recursive makes -j is passed so it ensures correct behavior. Order-only prerequisites Only existence is taken into account, not timestamp. OBJDIR := objdir OBJS := $(addprefix $(OBJDIR)/,foo.o bar.o baz.o) $(OBJDIR)/%.o : %.c $(COMPILE.c) $(OUTPUT_OPTION) $< $(OBJS): $(OBJDIR) $(OBJDIR): mkdir $(OBJDIR)

15 Extras II Multiple targets per rule targeta targetb: prerequisite recipe is equivalent to targeta: prerequisite recipe targetb: prerequisite recipe Distinguished with variable. Can be used to group targets by prerequisite. foo.o bar.o baz.o: common_header.h Useful options -B make all targets -n dry run (only prints commands) -d print what decisions are being made about dependencies

16 Reference GNU make manual

[Software Development] Makefiles. Davide Balzarotti. Eurecom Sophia Antipolis, France

[Software Development] Makefiles Davide Balzarotti Eurecom Sophia Antipolis, France 1 Software Development Tools 1. Configuring and Building the program GCC Makefiles Autotools 2. Writing and managing