Changes between Initial Version and Version 1 of Workshops/IntroToHpc2015/Programming/MakeFile

Timestamp:

10/12/15 16:03:55 (9 years ago)

Author:

pdejesus

Comment:

—

Workshops/IntroToHpc2015/Programming/MakeFile

@@ +1 @@
+= Basics of Makefile =
+[[http://en.wikipedia.org/wiki/Make_(software)|Wiki]]
+
+== !Subprogram/Module/Class ==
+* functions can be defined in separated files.
+  * subprogram/module (Fortran, C...)
+  * class (C++, python, Objective-C,Java...)
+* subprogram/module/class is defined for some specific purpose. one can use it without looking in the detail, just   know what inputs and outputs / functions...
+  * C module
+  * .c files: source code / functions
+  * .h files: header files, define functions and etc...
+
+== Makefile ==
+* A common way of automating software builds and other complex tasks with dependencies.
+* A Makefile is itself a program in a special language.
+* The command 'make' reads 'Makefile' and do some tasks.
+* Can specify file name 'make -f mymakefile'.
+* The default name is "Makefile"
+
+== Structure of Makefile ==
+Typical element in the simple Makefile:
+
+{{{
+target: dependencies
+[TAB] command to make target
+}}}
+
+It is important to use tab character, not spaces.
+
+command 'make target' means:
+* Make sure all the dependencies are up to date
+* If target is older than any dependency, recreate it using the specified commands.
+
+For example:
+{{{#!make
+#
+# Large Scale Computing
+# Heat / Mass Transfer
+#
+ALL: ex20 ex21
+#
+CC = gcc
+CFLAGS = -g
+#
+SRC_EX20 = ex20.c cg.c
+SRC_EX21 = ex21.c cg.c
+#
+OBJ_EX20 = $(SRC_EX20:.c=.o)
+OBJ_EX21 = $(SRC_EX21:.c=.o)
+#
+ex20 : $(OBJ_EX20)
+        $(CC) $(CFLAGS) -o $@ $(OBJ_EX20)
+ 
+ex21 : $(OBJ_EX21)
+        $(CC) $(CFLAGS) -o $@ $(OBJ_EX21)
+#
+%.o : %.c
+        $(CC) $(CFLAGS) -c $<
+cg.o : cg.c cg.h
+        $(CC) $(CFLAGS) -c cg.c 
+clean:  
+        rm -f *.o ex20
+}}}
+lines begin with # is comments
+
+== Age of dependency ==
+The last modification time of the file is used.
+{{{
+$ ls -l
+-rw-r--r--  1 fuji  staff    388 Sep 21 22:37 Makefile
+-rw-r--r--  1 fuji  staff   2030 Sep 21 19:31 cg.c
+-rw-r--r--  1 fuji  staff    838 Sep 21 19:31 cg.h
+-rw-r--r--  1 fuji  staff   4768 Sep 21 22:37 cg.o
+-rwxr-xr-x  1 fuji  staff  13308 Sep 22 09:44 ex20
+-rw-r--r--  1 fuji  staff   3035 Sep 21 22:39 ex20.c
+-rw-r--r--  1 fuji  staff   7728 Sep 22 09:44 ex20.o
+}}}
+* '''cg.c''' and '''cg.h''' to generate '''cg.o'''
+* '''ex20.c''' to generate '''ex20.o'''
+* '''ex20.o''' and '''cg.o''' to generate '''ex20'''
+Since all target files are newer than dependencies,
+
+{{{
+$ make
+make: Nothing to be done for `ALL'.
+}}}
+
+'''make''' command does not do anything.
+
+{{{
+$ touch cg.h
+$ ls -l
+-rw-r--r--  1 fuji  staff    388 Sep 21 22:37 Makefile
+-rw-r--r--  1 fuji  staff   2030 Sep 21 19:31 cg.c
+-rw-r--r--  1 fuji  staff    838 Sep 22 09:51 cg.h
+-rw-r--r--  1 fuji  staff   4768 Sep 21 22:37 cg.o
+-rwxr-xr-x  1 fuji  staff  13308 Sep 22 09:44 ex20
+-rw-r--r--  1 fuji  staff   3035 Sep 21 22:39 ex20.c
+-rw-r--r--  1 fuji  staff   7728 Sep 22 09:44 ex20.o
+}}}
+
+Now '''cg.h''' is newer than '''cg.o''',
+{{{
+$ make
+gcc -g -c cg.c
+gcc -g -o ex20 ex20.o cg.o
+}}}
+'''make''' command generates '''cg.o''' then generates '''ex20'''.
+
+
+== implicit rules ==
+General rule to make the *.o files from *.c files:
+{{{
+%.o : %.c %.h
+        gcc  -c $<
+}}}
+To make target
+{{{
+ex20 : $(OBJ_EX20)
+        gcc -o $@ $(OBJ_EX20)
+}}}
+== variables / macros ==
+{{{#!make
+CC = gcc
+CFLAGS = -g
+#
+SRC_EX20 = ex20.c cg.c
+SRC_EX21 = ex21.c cg.c
+#
+OBJ_EX20 = $(SRC_EX20:.c=.o)
+OBJ_EX21 = $(SRC_EX21:.c=.o)
+}}}
+
+[[http://www.gnu.org/software/make/manual/make.html|GNU make web pape]]