Okay so I need to make a basic Makefile for a program I wrote. Here are the files:
list.c
hash.c
order_book.c
libdefault_hash.a //provided already so I do not need to create.
I need to create libraries for list.c and hash.c so that orderbook can use them when it compiles. So this is what I currently have in Makefile:
all: orderbook
orderbook: orderbook.c liblist.a libhash.a
gcc -std=c99 -o orderbook order_book.c list.c -L. -llist -lhash -libdefault_hash
liblist.a: list.c
gcc -std=c99 -c list.c
ar rcu liblist.a list.o
libhash.a: hash.c
gcc -std=c99 -c hash.c
ar rcu libhash.a hash.o
My understanding of how makefiles work is very small but here is my thought process,
all: orderbook will mean that orderbook: will run.
orderbook.c will then compile, then the code will compile the libraries.
Once the libraries are compiled it will run:
gcc -std=c99 -o orderbook order_book.c list.c -L. -llist -lhash -libdefault_hash
And the result should be a simple program file named orderbook, but the terminal prints out:
$ make
gcc -std=c99 -o orderbook order_book.c list.c hash.c -L. -llist -lhash -libdefault_hash
/usr/lib/gcc/x86_64-pc-linux-gnu/4.6.3/../../../../x86_64-pc-linux-gnu/bin/ld: skipping incompatible ./liblist.a when searching for -llist
/usr/lib/gcc/x86_64-pc-linux-gnu/4.6.3/../../../../x86_64-pc-linux-gnu/bin/ld: cannot find -llist
/usr/lib/gcc/x86_64-pc-linux-gnu/4.6.3/../../../../x86_64-pc-linux-gnu/bin/ld: cannot find -libdefault_hash
collect2: ld returned 1 exit status
make: *** [orderbook] Error 1
$
Any help/guidance is much appreciated.
Let's take this in small steps. First, here's a sequence of commands that looks like what you have in mind:
gcc -std=c99 -c list.c -o list.o
ar rcu liblist.a list.o
gcc -std=c99 -c hash.c -o hash.o
ar rcu libhash.a hash.o
gcc -std=c99 -o orderbook order_book.c -L. -llist -lhash -libdefault_hash
Try these commands without Make, and see which ones work (are you sure "rcu" shouldn't be "-rcu"?). Tell us the results either by commenting on this answer or editing your question. Once any of these commands works, we can start writing the makefile.
Related
I have one program and it uses static or shared library. Now I want to do something like
make static
or
make shared
to compile the project in two cases.
My Makefile looks like
shared: main.o libresult.so
gcc -o shared main.o -L. -lresult -Wl,-rpath,.
main.o: main.c
gcc -c main.c
libresult.so: func.o
gcc -shared -o libresult.so func.o
func.o: func.c
gcc -c -fPIC func.c
static: main.o libresult.a
gcc -o static main.o -L. -lresult
main.o: main.c
gcc -c main.c
libresult.a: func.o
ar cr libresult.a func.o
func.o: func.c
gcc -c func.c
clean:
rm -f *.o *.a *.so static shared
Off course, terminal gives some warnings. It works well, but I dont think that
is much beautiful :). How to make it better?
1) You have two copies of the main.o rule:
main.o: main.c
gcc -c main.c
Delete one of them.
2) You have two versions of the func.o rule:
func.o: func.c
gcc -c -fPIC func.c
func.o: func.c
gcc -c func.c
This is a more serious problem. The object you put in the shared library (libresult.so) must be compiled with -fPIC; the object you put in the static library (libresult.a) may be compiled with -fPIC, but there is no reason to do so and it may prevent the compiler form performing some optimisation. Make doesn't know your intentions, so it is better to make two versions of the object with different names:
func_so.o: func.c
gcc -c -fPIC func.c -o func_so.o
func_a.o: func.c
gcc -c func.c -o func_a.o
(Don't forget to modify the rules that rely on these objects.)
3) Use automatic variables to reduce redundancy and make your makefile cleaner. For example:
main.o: main.c
gcc -c $< -o $#
Further improvements are possible, once you are comfortable with these.
I am working on a C project for Linux-environment (compiled with gcc). I am using two libraries:
SDL image (source is stored at the directory SDL_img).
SDL TTF (source is stored at the directory SDL_ttf).
My CFLAGS variable:
CFLAGS = -std=c99 -pedantic-errors -Wall -g -lm `sdl-config --cflags` -ISDL_img -ISDL_ttf
As you can see, I am including those two library-directories.
My gcc command include the following:
`sdl-config --libs` -lSDLmain -lSDL -lSDL_img -lSDL_ttf
Finally, in my project I have the following includes:
#include "SDL_ttf.h"
#include "SDL_image.h"
For some reason, I get errors of the type:
undefined reference to 'IMG_Load'
Why?
EDIT:
all: Chess.o Commons.o Console.o Controls.o Coords.o File.o GameState.o GUI.o Keyboard.o List.o Minimax.o Move.o Piece.o SettingsState.o Slots.o Square.o Str.o
gcc $^ -lm -std=c99 -pedantic-errors -g -o Chess `sdl-config --libs` -lSDLmain -lSDL -lSDL_img -lSDL_ttf
Just cd to those src/SDL_xxx dirs and do make to build those libraries and then set the correct -L and -I. It failed on linking so the -I is "good" but your path to your libraries is incorect
basically linker is now searching its paths to find libSDL_img and libSDL_ttf then it also searches /usr/lib/x86_64-linux-gnu and it still can not find it, that is why you are getting undefined referecne.
To fix this: first build those SDL_xxx and then search where are those libraries and pass somethig like this along with other to gcc:
-Lsrc/SDL_img/lib -lSDL_img -Lsrc/SDL_ttf/lib -lSDL_ttf
I am learning how to write C code in Linux and I am learning makefiles at a very beginner level.
I am having problems when making shared libraries.
The exercise is to make a simple function calculator C program with files:
main.c
add.c
subt.c
mult.c
div.c
The names of the files define the function they do.
The function in the file subt.c is in the static library:
libsubstatic.a
The function in the file mult.c is in the shared library:
libmultshared.so
For this program, I write the following makefile:
calc.exe: main.o add.o div.o libsubstatic.a libmultshared.so
gcc -o calc.exe main.o add.o div.o libsubstatic.a -Wl,-rpath,/home/ahmed/Desktop/labTask3 -lmultshared.so
main.o: main.c header.h
gcc -c main.c
add.o: add.c header.h
gcc -c add.c
libsubstatic.a: subt.o
ar cr libsubstatic.a subt.o
subt.o: subt.c header.h
gcc -c subt.c
libmultshared.so: mult.o
gcc -shared -fPIC -o libmultshared.so mult.o
mult.o: mult.c header.h
gcc -c -fPIC mult.c
div.o: div.c header.h
gcc -c div.c
The path where the code and makefile is placed:
/home/ahmed/Desktop/labTask3
I get the following message after I type "make" in the terminal:
gcc -o calc.exe main.o add.o div.o libsubstatic.a -Wl, -rpath, /home/ahmed/Desktop/labTask3 -lmultshared.so
gcc: error: unrecognized command line option ‘-rpath,’
make: *** [calc.exe] Error 1
What am I missing? Did I write this makefile correctly?
Please explain shared libraries, my concept might be faulty.
Please help.
Note that, I'm new to linux and I don't have much experience in makefiles.
EDIT: I removed the spaces as directed in the first answer. Now the terminal says:
gcc -o calc.exe main.o add.o div.o libsubstatic.a -Wl,-rpath,/home/ahmed/Desktop/labTask3 -lmultshared.so
/usr/bin/ld: cannot find -lmultshared.so
collect2: error: ld returned 1 exit status
make: *** [calc.exe] Error 1
Should I do something with the "-lmultshared.so"? What should I do?
-Wl, -rpath, /home/ahmed/Desktop/labTask3
Get rid of the spaces. This should all be one long argument.
-Wl,-rpath,/home/ahmed/Desktop/labTask3
See this excellent answer by #KerrekSB for a detailed explanation about passing arguments to the linker with -Wl.
I am trying to compile a very simple program using the -m32 flag.
If I try to do this using gcc -m32 it works just fine(I have the needed libs)
Yet, when I add this flag to my flags in a makefile, I get a weird error
This is the makefile that I have
CC=gcc
CFLAGS=-m32 -O1 -W -Wall -pedantic -std=c99
all: main.o
$(CC) -o main main.o
rm main.o
clean:
rm main
The error that I receive is the following
gcc -o main main.o
/usr/bin/ld: i386 architecture of input file `main.o' is incompatible with i386:x86-64 output
collect2: ld returned 1 exit status
make: *** [all] Error 1
Can someone please tell me what does this mean? and how can I fix it?
As for the code, the code does NOTHING except printing 'hello world'
I am using GCC 4.4.3 under Linux 2.6.35 64-bits
Your mistake is that you don't pass -m32 to the linker.
You actually need to change your Makefile to look like this:
CC=gcc
CFLAGS=-m32 -O1 -W -Wall -pedantic -std=c99
LDFLAGS = -m32
all: main.o
$(CC) $(LDFLAGS) -o main main.o
rm main.o
clean:
rm main
An even better approach would be the following Makefile:
CC=gcc
CFLAGS=-m32 -O1 -W -Wall -pedantic -std=c99
LDFLAGS=-m32
.INTERMEDIATE: main.o
all: main
main: main.o
clean:
-rm main
In the later you just say that main depends on main.o and GNU Make will invoke the linker with the LDFLAGS as arguments for you as it invokes the compiler with the CFLAGS as arguments for the main.o
"The targets which .INTERMEDIATE depends on are treated as intermediate files. See section Chains of Implicit Rules. .INTERMEDIATE with no dependencies marks all file targets mentioned in the makefile as intermediate." Special Built-in Target Names
You should inform the linker as well about the architecture being 32-bit. Try adding
LD = $(CC)
LDFLAGS = -m32
to your Makefile and change
$(CC) -o main main.o
to
$(LD) $(LDFLAGS) -o main $^
and it shoud work.
(Why it worked? If you use GCC to compile and link your code in one step, all the relevant flags and options will be passed down not only to the compiler but to the linker as well.)
Am facing a problem that may be slightly complicated to explain and understand as giving the entire picture would be too big and difficult.
Please excuse me for it.
Consider the following Makefile:
all: clients.so simulator backup
LD_PRELOAD=/home/Juggler/client/clients.so ./simulator
backup: backup.c libclient.a
gcc backup.c -o backup -L /home/Juggler/client -L. -lclient -ldl
simulator: simulator.c libclient.a
gcc -g simulator.c -o simulator -L /home/Juggler/client -L. -lclient -ldl -pthread
libclient.a: libclient.o client.o
ar rcs libclient.a libclient.o client.o
libclient.o:libclient.c
gcc -c libclient.c -o libclient.o -pthread
clients.so: client.o client_invoke.o
ld -shared -o clients.so client_invoke.o client.o -ldl
client_invoke.o: client_invoke.c
gcc -Wall -fPIC -DPIC -c -g client_invoke.c
client.o: client.c
gcc -Wall -fPIC -DPIC -c -g client.c -ldl -pthread
We call function written in client.c from libclient.c and these functions in client.c make call to pthread_key_create(), pthread_setspecific..etc.
Threads are created by simulator.c and theses threads access functions written in he other files.
On doing make...Errors like the following appear.
/home/Juggler/client/libclient.a(client.o):In function 'setup_connection':
/home/Juggler/client/client.c:35: undefined reference to 'pthread_setspecific'
pthread.h has been included in both client.c and libclient.c
Would be grateful for anypointers . I understand information is very less...
Thanks
On linux, pthread functions live in the libpthread library. So you have to link to that.
The proper way, when using pthreads, is to compile and link using the -pthread , which, among other things, will link in the pthread library. You have the -pthread flag for some of your executables, but not for others, and not for your clients.so library, so add the flag where required.
Also, remember, when you are creating a shared library, you should compile the source files with the -fPIC flag.
(And, seems you are calling ld directly to produce the client.so library, you really should use gcc to do the linking.)