It seems I'm having issues with the pthread when I try compiling with a Makefile:
/csapp.c:462: undefined reference to `pthread_create'
I think it might have something to do with the -lpthread?
Here is my Makefile (yes they are tabbed once):
CC = gcc
CFLAGS = -Wall -g
LDFLAGS = -lpthread
OBJS = proxy.o csapp.o
all: proxy
proxy: $(OBJS)
csapp.o: csapp.c
$(CC) $(CFLAGS) -c csapp.c
proxy.o: proxy.c
$(CC) $(CFLAGS) -c proxy.c
clean:
rm -f *~ *.o proxy
I believe your problem is with LDFLAGS.
From 10.3 Variables Used by Implicit Rules:
LDFLAGS Extra flags to give to compilers when they are supposed to invoke the linker, ld, such as -L. Libraries (-lfoo) should be added to the LDLIBS variable instead.
LDLIBS Library flags or names given to compilers when they are supposed to invoke the linker, ld. LOADLIBES is a deprecated (but still supported) alternative to LDLIBS. Non-library linker flags, such as -L, should go in the LDFLAGS variable.
So try:
LDLIBS = -lpthread
Related
I am trying to compile a C language library as a shared object on my new install of Fedora 22. The project compiled fine on my old install of Fedora 20. But now, when I run my makefile:
CC=gcc
vpath %.c src
vpath %.h inc
CFLAGS = -fPIC
INCLUDE = -Iinc -I/usr/include -I/usr/local/include
LIBPATH = -L/usr/lib -L/lib64
LIBS = -lportaudio -lm -lpthread -ldl
OBJ_PATH = ./objs
SRCS = my_code1.c my_code2.c # etc.
OBJS = $(SRCS:.c=.o)
.PHONY: libmylib.so
all: libmylib.so
debug: $(CFLAGS) += -DDEBUG -O0 -g3 -DPD
debug: all
release: $(CFLAGS) += -DTESTING -O2 -DPD -funroll-loops -fomit-frame-pointer
release: all
%.o: %.c
$(CC) $(CFLAGS) $(INCLUDE) $(LIBPATH) $(LIBS) -c -o $# $^
libmylib.so: $(OBJS)
$(CC) -shared -Wl,-soname,libmylib.so \
-Wl,--no-undefined $(OBJS) -lc -lportaudio -ldl -lm -lpthread
mv libmylib.so ./bin
mv *.o $(OBJ_PATH)
clean:
rm $(OBJ_PATH)/*.o
rm bin/libmylib.so
I get very many undefined reference errors:
my_code1.o: In function `func_in_my_code1':
my_code1.c:(.text+0x1b8): undefined reference to `func_from_my_code2'
my_code2.o: In function `func_in_my_code2':
my_code2.c:(.text+0x310): undefined reference to `func_from_my_func1'
The functions in question are most certainly defined in the code. Presumably these are compiled into .o files in the compile stage.
The exact same build environment worked on my previous fedora installation. I am at a loss as to why I should get these errors.
Also, if I compile without the -Wl,--no-undefined flag, it compiles fine, but when I try to load the library from another application, it tosses the same set of undefined errors.
This may have nothing to do with the new version of Fedora. It is possible that there are some environment variables or something that didn't make through to my new install, but I have no idea what they could be.
Apparently I now need to insert the extern keyword into these functions. The code compiled and ran perfectly well before... I would like to reiterate, for posterity's sake, that I did post the entire makefile in my question.
A static library is linked fine in the command line, but not through makefile. Compiling part accessing include files seems ok, but ld process must be wrong in the makefile.
Thanks for your help in advance!
Here is my command line:
gcc -o quadEq.exe quadEq.c -I../include -L../lib -lnowic
Here is my Makefile:
CFLAGS = -Wall -g -c
INCLUDE = -I../include
LDFLAGS = -L../lib
LDLIBS = -lnowic
SOURCES = quadEq.c
OBJECTS = $(SOURCES:.c=.o)
EXE = quadEq
all: $(SOURCES) $(EXE)
$(EXE): $(OBJECTS)
gcc $(OBJECTS) $(LDFLAGS) $(LDLIBS) -o $#
.c.o:
gcc $(CFLAGS) $(INCLUDE) $< -o $#
Here is my screen capture that ran Makefile and the command line.
Static libraries care in which order you link them. If libA.a depends on libB.a, then you have to do -lB -lA.
If a libA.a symbol depends on libB.a that depends on a libA.a symbol, you have to cyclically link: -lB -lA -lB. I've seen some cycles get to about 3 or 4 loops, but generally 2 is enough in my experience.
This is different from dynamic library linking which not only doesn't care what order you link them, but you don't need to also link dependent libraries since the .so specifies them.
Based on Aggieboy's suggestions, I rewrote the makefile and made it work.;
CC = gcc
CFLAGS = -x c -Wall -g
INCPATH = -I../include
LIBPATH = -L../lib
LLIBS = -lnowic
%: %.c
$(CC) -o $# $(CFLAGS) $(INCPATH) $< $(LIBPATH) $(LLIBS)
By the way, this accepts a filename to make from the command line argument.
Thank you Aggieboy again!
I'm experiencing some compilation issues with my dynamic library. It should be linked to main.c but for all references to it I receive "undefined reference to function_name".
The contents of main.c isn't really that important; I include my library:
#include "matrix.h"
Then I have a simple Makefile to link the two.
#Variables
LIB = matrix
# Usual compilation flags
CFLAGS = -std=c99 -Wall -Wextra -g
CPPFLAGS = -I../include -DDEBUG
LDFLAGS = -lm
# Special rules and targets
.PHONY: all clean help
all: $(LIB).o libmatrix.so main
$(LIB).o: $(LIB).c $(LIB).h
$(CC) $(CFLAGS) $(CPPFLAGS) -fPIC -c -o $# $<
libmatrix.so: $(LIB).o
$(CC) $(CFLAGS) -fPIC -shared -o $# $< $(LDFLAGS)
main: main.o libmatrix.so
$(CC) $(CFLAGS) -o $# $< -L -lmatrix
Can anyone direct me to where I might be going wrong? Many thanks in advance.
You probably want -L. not -L in your last line, so:
main: main.o libmatrix.so
$(CC) $(CFLAGS) -o $# $< -L. -lmatrix
You should read Program Library HOWTO and Drepper's paper: How to Write Shared Libraries; you might want to set some -rpath at link time (maybe using -Wl,-rpath,. ...), and you might want to link with -rdynamic ....
Alternatively, set your LD_LIBRARY_PATH environment variable to contain . (I don't recommend that), or install your shared library in /usr/local/lib/ (and add it to /etc/ld.so.conf then run ldconfig). See also dlopen(3), environ(7), ld.so(8), ldconfig(8)
I want to create a makefile that supports posix semaphores.
That is what I've got so far:
CFLAGS=-g -ansi -pedantic -Wall -Werror -D_XOPEN_SOURCE=600
LDFLAGS=-pthread
CC=gcc
OBJECTS=MsgQueueMain.o MsgQueue.o Queue.o MyMalloc.o
TARGET=MsgQueueMain
all: $(TARGET)
$(TARGET): $(OBJECTS)
$(CC) $(OBJECTS) -o $#
include depends
depends:
$(CC) -MM $(OBJECTS:.o=.c) > depends
clean:
rm ./$(TARGET) *.o
For some reason, I'm getting "undefined reference" for all calls to semaphore.h api functions.
You need to link with the rt or pthread library. From man sem_destroy reference page:
Link with -lrt or -pthread.
Add to the end of the compiler command as order is important (unsure if order is important for -pthread as this defines some macros and adds -lpthread).
As commented by Vlad Lazarenko the LDFLAGS is not part of your TARGET. Change to:
$(CC) $(OBJECTS) -o $# $(LDFLAGS)
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Linker errors when compiling against glib…?
Okay, I know this may be a duplicate, but I can't find any other answer to my problem.
I am trying to install Pintos and when I run 'make' in the src/utils directory, I get the error that there is an undefined reference to 'floor'. I checked the makefile and here's what I got:
all: setitimer-helper squish-pty squish-unix
# 2207718881418
CC = gcc
CFLAGS = -Wall -W
LDFLAGS = -lm
setitimer-helper: setitimer-helper.o
squish-pty: squish-pty.o
squish-unix: squish-unix.o
clean:
rm -f *.o setitimer-helper squish-pty squish-unix
I tried adding LIBS = -lm but that didn't help.
Output of make:
gcc -lm setitimer-helper.o -o setitimer-helper
setitimer-helper.o: In function `main':
setitimer-helper.c:(.text+0xbb): undefined reference to `floor'
collect2: ld returned 1 exit status
make: *** [setitimer-helper] Error 1
Any solutions to this dilemma?
Your original makefile defines a bunch of variables
CC = gcc
# etc
and lists some dependencies
setitimer-helper: setitimer-helper.o
# etc
but doesn't have any recipes giving the exact commands to be used to remake the targets, except for the clean rule. This means that built-in implicit rules will be used; e.g., to link setitimer-helper the following built-in rule will be used:
$(CC) $(LDFLAGS) $^ $(LDLIBS) -o $#
For setitemer-helper, the automatic variables are filled in using the relevant dependency:
$(CC) $(LDFLAGS) setitimer-helper.o $(LDLIBS) -o setitimer-helper
and from this you can see how the remaining variables -- $(CC), $(LDFLAGS), and $(LDLIBS) -- were filled in to give the output of make that you saw.
As various people have noted, you need to make sure that -lm goes at the end of the link command so that it can be used to satisfy references to library functions like floor(). At the moment, your makefile sets $(LDFLAGS) to -lm, but that variable is used at the start of the link command.
The conventional variables are set up in this built-in rule so that LDFLAGS can be used for options (a.k.a. "flags") that (historically) need to be at the start of the link command, and LDLIBS can be used for libraries that need to be specified after the *.o object files.
So to fix this in terms of the makefile you are using, you need to remove -lm from the LDFLAGS variable that is defined, and instead add another variable definition for LDLIBS:
LDLIBS = -lm
(I'm oversummarising slightly: the built-in rule also contains $(TARGET_ARCH) and $(LOADLIBES), but those aren't of interest here.)
It's compiled in wrong order, the way to proceed is:
CC = gcc
CFLAGS = -Wall -W
LDFLAGS = -lm
myprog: myprog.o more_code.o
${CC} ${CFLAGS} myprog.o more_code.o ${LDFLAGS} -o myprog
myprog.o: myprog.c
${CC} ${CFLAGS} -c myprog.c
more_code.o: more_code.c
${CC} ${CFLAGS} -c more_code.c
clean:
\rm myprog.o more_code.o myprog
More info: http://www.physics.utah.edu/~p5720/rsrc/make.html
Can you show me in terms of the original makefile?
I can try :)
CC = gcc
CFLAGS = -Wall -W
LDFLAGS = -lm
OBJECTS = setitimer-helper.o squish-pty.o squish-unix.o
all: setitimer-helper
setitimer-helper: $(OBJECTS)
${CC} ${CFLAGS} $(OBJECTS) ${LDFLAGS} -o setitimer-helper
setitimer-helper.o: setitimer-helper.c
${CC} ${CFLAGS} -c setitimer-helper.c
squish-pty.o: squish-pty.c
${CC} ${CFLAGS} -c squish-pty.c
squish-unix.o: squish-unix.c
${CC} ${CFLAGS} -c squish-unix.c
And since you are new to Makefile, it's a good idea to add -Wextra -pedantic to CFLAGS