I am trying to use an external library called iniparser in my C program. I'm using gcc 4.4.
I put the iniparser library in a subdirectory called lib/ header files are in lib/iniparser/src and the library is compiled to lib/iniparser/libiniparser.so.0.
I wrote a short Makefile to compile it, here's the output of make:
gcc -Wall -Wextra -Werror -c -I include/ src/smag_main.c -L lib/iniparser -liniparser -I lib/iniparser/src
gcc -Wall -Wextra -Werror -c -I include/ -L lib/iniparser -liniparser -I lib/iniparser/src src/agros.c
gcc -Wall -Wextra -Werror -c -I include/ -L lib/iniparser -liniparser -I lib/iniparser/src src/main.c
gcc -Wall -Wextra -Werror -L lib/iniparser -liniparser -o agros smag_main.o main.o agros.o
smag_main.o: In function `sec_haskey':
smag_main.c:(.text+0xa9): undefined reference to `iniparser_find_entry'
smag_main.o: In function `parse_config':
smag_main.c:(.text+0x153): undefined reference to `iniparser_load'
smag_main.c:(.text+0x18b): undefined reference to `iniparser_getint'
smag_main.c:(.text+0x1c6): undefined reference to `iniparser_getstring'
smag_main.c:(.text+0x202): undefined reference to `iniparser_getstring'
smag_main.c:(.text+0x261): undefined reference to `iniparser_getstring'
smag_main.c:(.text+0x2c2): undefined reference to `iniparser_getint'
smag_main.c:(.text+0x2d5): undefined reference to `iniparser_freedict'
collect2: ld returned 1 exit status
make: *** [agros] Error 1
First call to gcc compiles smag_main.o successfully, the second one compiles agros.o and the third one main.o. The 4th call is the linker, that will link all those objects into an executable agros. It obviously fails.
It looks like it has problems locating iniparser.so at linking time. How's my call wrong?
I am confused.
(Alternate question, if anyone could explain how to the linking by calling ld directly it would be great).
Try putting a symlink from libiniparser.so.0 to libiniparser.so
cd lib/iniparser/
ln -s libiniparser.so.0 libiniparser.so
Related
I am trying to make a shared library which consists of one C header file and two C source files, one of which calls a Python file for implementation.
The compilation comand used is
gcc -fPIC -c -I-I/usr/local/include -I/usr/local/include -I/usr/local/include/python3.4m -I/usr/local/include/python3.4m -DNDEBUG -g -fwrapv -O0 -Wall -Wstrict-prototypes -DDOUBLE_PRECISION *.c
I am able to compile all these without any error, but when I try to make a shared object file using the following command
gcc *.o -L/usr/local/lib -lpthread -ldl -lutil -lm -Xlinker -export-dynamic /usr/local/lib/python3.4/config-3.4m/libpython3.4m.a -shared -o libroughness.so
I get the following error which I am unable to resolve
/usr/bin/ld: /usr/local/lib/python3.4/config-3.4m/libpython3.4m.a(abstract.o): relocation R_X86_64_32S against `_PyObject_NextNotImplemented' can not be used when making a shared object; recompile with -fPIC
/usr/local/lib/python3.4/config-3.4m/libpython3.4m.a: could not read symbols: Bad value
collect2: ld returned 1 exit status
I am using -fPIC tag while compilation, however it still asks me to recompile with fPIC. Any help on how to resolve this case would be appreciated.
I'm trying to install PintOS on my local Ubuntu 14.04 machine. When I try to run make to compile the utilities. I get the following error.
ankitkal#ankitkal-Inspiron-5521:~/os/pintos/src/utils$ ls
backtrace Makefile pintos pintos.~1.55.~ pintos-mkdisk setitimer-helper.o squish-unix.c
CVS Makefile~ pintos~ pintos-gdb setitimer-helper.c squish-pty.c
ankitkal#ankitkal-Inspiron-5521:~/os/pintos/src/utils$ make
gcc -lm setitimer-helper.o -o setitimer-helper
setitimer-helper.o: In function `main':
setitimer-helper.c:(.text+0xbe): undefined reference to `floor'
collect2: error: ld returned 1 exit status
make: *** [setitimer-helper] Error 1
ankitkal#ankitkal-Inspiron-5521:~/os/pintos/src/utils$
The maths library (for the <math.h> header which is used in setitimer-helper.c) is not getting linked properly. When I look into the Makefile, this is the output.
ankitkal#ankitkal-Inspiron-5521:~/os/pintos/src/utils$ cat Makefile
all: setitimer-helper squish-pty squish-unix
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
Please tell me how to fix it. I'm using gcc-4.8.6 by the way.
gcc -lm setitimer-helper.o -o setitimer-helper
The problem is in the order of your arguments to GCC. Try this:
gcc -o setitimer-helper setitimer-helper.o -lm
This is because of the way that ld resolves undefined symbols when linking. Basically, the way you had it before, ld first sees -lm and says "I have no reason to include this library". It then includes your setitimer-helper.o which has an unresolved reference to floor. After that, there are no more libraries to consider, and floor remains unresolved.
If -lm comes afterward, it is able to resolve the reference to floor.
I'm new to C programming, and I'm trying to compile this Simple training example with GCC on Ubuntu 12.10.
Looks like fann.h should not be included (as stated on the file itself), so I included fixedfann.h instead.
First attempt (without include, just to see what the compiler will ask for):
$ gcc main.c -o output
/tmp/cckKyM92.o: In function `main':
main.c:(.text+0x62): undefined reference to `fann_create_standard'
main.c:(.text+0x7a): undefined reference to `fann_set_activation_function_hidden'
main.c:(.text+0x8e): undefined reference to `fann_set_activation_function_output'
main.c:(.text+0xba): undefined reference to `fann_train_on_file'
main.c:(.text+0xce): undefined reference to `fann_save'
main.c:(.text+0xda): undefined reference to `fann_destroy'
collect2: ld returned 1 exit status
fann_create_standard is on fann.h and fann.c. As fann.h is included by fixedfann.h, and fann.h should not be included directly, I believe I have to compile fann.c and fixedfann.c, and link then (tell me if I'm doing any mistake, I'm still not familiar with this "linking" stuff).
So I did:
$ gcc fann/fixedfann.c -o fann/fixedfann.o
fann/fixedfann.c:22:20: fatal error: config.h: No such file or directory
compilation terminated.
and then I did:
$ gcc fann/fixedfann.c -o fann/fixedfann.o -include fann/include/config.h
fann/fixedfann.c:22:20: fatal error: config.h: No such file or directory
compilation terminated.
Now, why it's not finding the config.h file here?
--update
Thanks #JonathanLeffler, I could make some steps here. But now I'm stuck at:
$ gcc fann/fixedfann.c -o fann/fixedfann.o -I./fann/include/ -lm
/usr/lib/gcc/i686-linux-gnu/4.6/../../../i386-linux-gnu/crt1.o: In function `_start':
(.text+0x18): undefined reference to `main'
collect2: ld returned 1 exit status
and, with grep, I could not find any reference to main on the fann folder... Also no function _start, and I don't know who is linking this crt1.o... Any idea what's wrong here?
--update2
Ok, I got the .o files using Harmeet's Makefile, now I'm trying to link everything.
I created the main.o with gcc -c main.c, and I tried:
gcc -o output main.o fann/fixedfann.o -lm
(-lm for the libmath, that is needed) and I got:
main.c:(.text+0xba): undefined reference to `fann_train_on_file'
This fann_train_on_file is on fann_train_data.c, so I tried:
gcc -o output main.o fann/fixedfann.o fann/fann_train_data.o -lm
but I got lots of multiple definition of... errors... :/
Looks like fann_train_data.o is already included/linked, but if so, why it's not finding fann_train_on_file?
--update3
I'm still really stuck here... Any idea of which (if any) of this two lines should work?:
gcc -o output main.o hello.o fann/fixedfann.o fann/fann_train_data.o -lm
or
gcc -o output main.o hello.o fann/fixedfann.o -lm
--update for Harmeet
The output was:
$ make
gcc -L./fann -lfann main.o -o main
main.o: In function `main':
main.c:(.text+0x62): undefined reference to `fann_create_standard'
main.c:(.text+0x7a): undefined reference to `fann_set_activation_function_hidden'
main.c:(.text+0x8e): undefined reference to `fann_set_activation_function_output'
main.c:(.text+0xba): undefined reference to `fann_train_on_file'
main.c:(.text+0xce): undefined reference to `fann_save'
main.c:(.text+0xda): undefined reference to `fann_destroy'
collect2: ld returned 1 exit status
make: *** [main] Error 1
You can use ar to make a static library and work with that.
Create a Makefile under your hello-fann-3/fann/ folder with the following contents -
SOURCES = $(wildcard *.c)
OBJECTS = $(SOURCES:.c=.o)
CFLAGS = -c -Iinclude
all: libfann.a
libfann.a: $(OBJECTS)
ar rcs $# $^
%.o: %.c
gcc $(CFLAGS) $^
Then use the make command in hello-fann-3/fann/ to build the static library. The above Makefile will generate libfann.a that you can link to your program.
Create a Makefile under your hello-fann-3/ folder with the following contents -
SOURCES = $(wildcard *.c)
OBJECTS = $(SOURCES:.c=.o)
CFLAGS = -c -I./fann/include
LFLAGS = -L./fann -lfann
main: $(OBJECTS)
gcc $(LFLAGS) $^ -o $#
%.o: %.c
gcc $(CFLAGS) $^
Then use the make command in hello-fann-3/ to build the main program.
In your main.c, you must include fan.h like -
#include "fann.h"
If you do not understand the Makefile, you can read about it here -
http://www.gnu.org/software/make/manual/html_node/index.html
You just need to link the fann library.
If you compile manually do this
gcc main.c -lfann -lm -o main
then simply run it like
./main
If you are on Ubuntu and you faced the following error
./main: error while loading shared libraries: libfann.so.2: cannot open shared object file: No such file or directory
Then run
sudo ldconfig
If you are using NetBeans, then simply Right click on your project -> Properties -> Build -> Linker,
then in the Libraries section click on the browse button [...] then in the new window click on Add Library...
Then add fann library (for example my fann library path is: /usr/local/lib/libfann.a) and click Ok
A fellow helped me, and we came to this line that compiled everything, and make the executable:
$ gcc fann/fann.c fann/fann_io.c fann/fann_train.c fann/fann_train_data.c fann/fann_error.c fann/fann_cascade.c main.c -Ifann/include -lm
And this is the answer.
That said, this is exactly what fixedfann.c is doing (include all this .c files). But if I try:
$ gcc fann/fixedfann.c main.c -Ifann/include -lm
..I get:
undefined reference to `fann_train_on_file'
This fann_train_on_file is on fann_train_data.c, which is included by fixedfann.c, so why it is undefined? I don't know... :/
--update
I realized that:
$ gcc fann/fixedfann.c main.c -Ifann/include -lm
will work if I comment the headers on fixedfann.c:
//#include "config.h"
//#include "fixedfann.h"
#include "fann.c"
#include "fann_io.c"
#include "fann_train.c"
#include "fann_train_data.c"
#include "fann_error.c"
#include "fann_cascade.c"
I'm trying to compile my project and I use the lib ncurse. And I've got some errors when compiler links files.
Here is my flags line in Makefile:
-W -Wall -Werror -Wextra -lncurses
I've included ncurses.h
Some layouts :
prompt$> dpkg -S curses.h
libslang2-dev:amd64: /usr/include/slcurses.h
libncurses5-dev: /usr/include/ncurses.h
libncurses5-dev: /usr/include/curses.h
prompt$> dpkg -L libncurses5-dev | grep .so
/usr/lib/x86_64-linux-gnu/libncurses.so
/usr/lib/x86_64-linux-gnu/libcurses.so
/usr/lib/x86_64-linux-gnu/libmenu.so
/usr/lib/x86_64-linux-gnu/libform.so
/usr/lib/x86_64-linux-gnu/libpanel.s
And here are my erros :
gcc -W -Wall -Werror -Wextra -I./Includes/. -lncurses -o Sources/NCurses/ncurses_init.o -c Sources/NCurses/ncurses_init.c
./Sources/NCurses/ncurses_init.o: In function `ncruses_destroy':
ncurses_init.c:(.text+0x5): undefined reference to `endwin'
./Sources/NCurses/ncurses_init.o: In function `ncurses_write_line':
ncurses_init.c:(.text+0xc5): undefined reference to `mvwprintw'
./Sources/NCurses/ncurses_init.o: In function `ncurses_init':
ncurses_init.c:(.text+0xee): undefined reference to `initscr'
collect2: error: ld returned 1 exit status
Thanks a lot
You need to change your makefile so that the -lncurses directive comes after your object code on the gcc command line, i.e. it needs to generate the command:
gcc -W -Wall -Werror -Wextra -I./Includes/. -o Sources/NCurses/ncurses_init.o -c Sources/NCurses/ncurses_init.c -lncurses
This is because object files and libraries are linked in order in a single pass.
In C++ , I fixed it just by linking the ncurses library .
Here is the command :
g++ main.cpp -lncurses
I got flags to correct order by using LDLIBS variable:
ifndef PKG_CONFIG
PKG_CONFIG=pkg-config
endif
CFLAGS+=-std=c99 -pedantic -Wall
LDLIBS=$(shell $(PKG_CONFIG) --libs ncurses)
man gcc | grep -A10 "\-l library"
-l library
Search the library named library when linking. (The second alternative with the library as a separate argument is only for POSIX
compliance and is not recommended.)
It makes a difference where in the command you write this option; the linker searches and processes libraries and object files
in the order they are specified. Thus, foo.o -lz bar.o searches
library z after file foo.o but
before bar.o. If bar.o refers to functions in z, those functions may not be loaded.
Why am I getting an "undefined reference" error using gcc?
I am trying to create a shared object (.so) that exports one function, "external()". I then try to link against the .so but get "undefined reference 'external'". What am I doing wrong here?
File: external.c
int external() {
return 5;
}
File: program.c
int external();
int main(char** argv, int* argc) {
return external();
}
Commands:
$ gcc -fPIC -c external.c
$ gcc -shared -o libexternal.so external.o
$ gcc -L. -lexternal -o program program.c
/tmp/cc3MmhAE.o: In function `main':
program.c:(.text+0x7): undefined reference to `external'
collect2: ld returned 1 exit status
I can even run nm and see that the .so is defining 'external':
Command:
$ nm libexternal.so | grep external
0000040c T external
What am I missing here?
Recent versions of gcc/ld default to linking with --as-needed.
This means if you write -lexternal before the C file the library will automatically get excluded (the order matters when testing if things are "needed" like this)
You can fix this with either of:
gcc -L. -o program program.c -lexternal
gcc -L. -Wl,--no-as-needed -lexternal -o program program.c
The latter of which passes --no-as-needed to the linker, which would cause the library to still be linked, even if you didn't call external() from it.
Note: -Wl,--no-as-needed isn't applied globally to everything that's linked, it's only applied to things that follow it in the command line order. So -lexternal -Wl,--no-as-needed also wouldn't work. This does mean that you can mix and match behaviours though, for example gcc -L. -Wl,--no-as-needed -lexternal -Wl,--as-needed -o program program.c -lmightneed would always link against external, but only link against mightneed if one or both of program.c/libexternal.so caused it to be needed.