I have written this make file and when I tried to execute it gcc compiler occurs errors
cc=gcc
CFLAGS=-I
LDLIBS=-lpthread
OBJECTS= MP.o serial.o MT.o
program:$(OBJECTS)
$(cc) $(CFLAGS) $(OBJECTS) $(LDLIBS) -o program
and this is the message of errors
gcc -I MP.o serial.o MT.o -lpthread -o program
MT.o: In function `main':
MT.c:(.text+0x2bf): multiple definition of `main'
serial.o:serial.c:(.text+0x0): first defined here
collect2: error: ld returned 1 exit status
make: *** [program] Error 1
I am sure that there is no wrong in the 3 files individually
Can anyone tell me what's wrong with my make file?
Can anyone tell me what's wrong with my make file?
The error is not in the makefile, read the linker error:
MT.c:(.text+0x2bf): multiple definition of `main'
serial.o:serial.c:(.text+0x0): first defined here
It's telling you that main is defined twice, first in serial.c and then again in MT.c
The problem is in your program, not the makefile.
(You do also have a broken CFLAGS variable with no path, but that's not the main problem.)
Related
I need to upload a .cpp file for a course application. The code works, i tried their test inputs, but when i upload my file it throws this error
</usr/lib/gcc/x86_64-linux-gnu/7/../../../x86_64-linux-gnu/crt1.o: In function _start': (.text+0x20): undefined reference to main'
collect2: error: ld returned 1 exit status>
On the website it has a list of compilation commands that I assume have to somehow put into my code so the website can process my code?
Maybe that isnt even it, this is my first time dealing with this sort of thing, so any help is appreciated.
Tried just putting it into the code outside of main, didnt work.
I am trying to make a shared library for a particular problem I was working on. It has "point_sense.c" as the main file which uses functions defined in "createPolygon.c." The functions are declared in a header file "createPolygon.h."
To compile them, I used a makefile which looks like the following
all:point_sense
createPolygon.o:createPolygon.c
g++ -c -fpic createPolygon.c
libcreatePolygon.so:createPolygon.o
g++ -shared -o libcreatePolygon.so createPolygon.o
point_sense:point_sense.c libcreatePolygon.so
g++ -o point_sense -L~Desktop/Summer_2020_linux/tutorials/cpp_practise point_sense.c -lcreatePolygon
clean:
rm point_sense createPolygon.o libcreatePolygon.so
but when I make the file, it gives an output as
g++ -c -fpic createPolygon.c
g++ -shared -o libcreatePolygon.so createPolygon.o
g++ -o point_sense -L~Desktop/Summer_2020_linux/tutorials/cpp_practise point_sense.c -lcreatePolygon
/usr/bin/ld: cannot find -lcreatePolygon
collect2: error: ld returned 1 exit status
make: *** [makefile:10: point_sense] Error 1
Initially I thought this was some silly mistake, and to check I used
ld -L~/Desktop/Summer_2020_linux/tutorials/cpp_practise -lcreatePolygon -verbose
and after a long output I got (a few unimportant lines in the code are skipped in between)
ld: mode elf_x86_64
attempt to open ~/Desktop/Summer_2020_linux/tutorials/cpp_practise/libcreatePolygon.so failed
attempt to open ~/Desktop/Summer_2020_linux/tutorials/cpp_practise/libcreatePolygon.a failed
attempt to open /usr/local/lib/x86_64-linux-gnu/libcreatePolygon.so failed
attempt to open /usr/local/lib/x86_64-linux-gnu/libcreatePolygon.a failed
.
.
.
ld: cannot find -lcreatePolygon
But when I try to open 'libcreatePolygon.so' directly, I am able to open it.
$ nano ~/Desktop/Summer_2020_linux/tutorials/cpp_practise/libcreatePolygon.so
There are several threads which explain the process of doing this, but I don't see what it is that I am doing wrong. Any help is appreciated.
I am using Ubuntu 20.04.1 LTS and g++ (Ubuntu 9.3.0-10ubuntu2) 9.3.0 .
I tried to reproduce the problem here, and this error message goes away if you put a space between the -L flag and the tilde character.
The reason is: if there is no space between -L and ~, the tilde character cannot be expanded to the home directory.
Hi I've never written a makefile before, but I tried my hand at it with my fortran90 final project and the makefile seems to have delete my main program. here's my makefile
# Sample makefile for several modules
#
FC = gfortran
final.x: subs.o func.o maina.o
gfortran -o final.x subs.o func.o maina.o
subs.o: subs.f90
gfortran -c subs.f90
func.o: func.f90
gfortran -c func.f90
maina.o: maina.f90
gfortran -c maina.f90
after running this, my maina.f90 was deleted and the I did not have a copy. this was what it showed when it was running. (The first output is when I ran it and found an error in subs, and after fixing these errors, I got the second output)
$ make
gfortran -o final.x subs.o func.o maina.o
subs.o: In function `__subs_MOD_gauss':
subs.f90:(.text+0x350): undefined reference to `f_'
subs.f90:(.text+0x366): undefined reference to `f_'
subs.o: In function `__subs_MOD_simp':
subs.f90:(.text+0x434): undefined reference to `f_'
subs.f90:(.text+0x4a2): undefined reference to `f_'
subs.f90:(.text+0x51b): undefined reference to `f_'
subs.o:subs.f90:(.text+0x571): more undefined references to `f_' follow
collect2: ld returned 1 exit status
make: *** [final.x] Error 1
$ make
gfortran -c subs.f90
gfortran -o final.x subs.o func.o maina.o
does anyone know why this file deleted my maina.f90, or (though it's probably unlikely) how to get my work back?
EDIT- I should add that I do not have admin or sudo privileges on this computer
This question already has answers here:
What is an undefined reference/unresolved external symbol error and how do I fix it?
(39 answers)
Closed 4 years ago.
I am trying to compile a Fortran 90 code that uses HDF5. For that purpose, I am using the following Makefile:
# Location of HDF5 binaries (with include/ and lib/ underneath)
HDF5 = /fs/posgrado16/other0/guido/libraries/hdf5/serial
# Compiler
FC = gfortran
# ------ No machine-specific paths/variables after this -----
FORTRANLIB=-I$(HDF5)/include $(HDF5)/lib/libhdf5_fortran.a
FSOURCE = h5_crtgrpar.f90
OBJECTS = $(FSOURCE:.f90=.o)
EXECUTABLE = $(FSOURCE:.f90=.exe)
LIBSHDF = $(FORTRANLIB) $(HDF5)/lib/libhdf5.a
all:$(EXECUTABLE)
$(EXECUTABLE):$(OBJECTS)
$(FC) -o $# $^ $(LIBSHDF)
$(OBJECTS):$(FSOURCE)
$(FC) -c $# $< $(LIBSHDF)
.PHONY : clean
clean:
rm -f $(FSOURCE) $(OBJECTS) *.h5
But, I get the following error:
$ make -f Makefilef
gfortran -o h5_crtgrpar.exe h5_crtgrpar.o -I/fs/posgrado16/other0/guido /libraries/hdf5/serial/include /fs/posgrado16/other0/guido/libraries/hdf5/serial/lib/libhdf5_fortran.a /fs/posgrado16/other0/guido/libraries /hdf5/serial/lib/libhdf5.a
/fs/posgrado16/other0/guido/libraries/hdf5/serial/lib/libhdf5.a(H5PL.o): In function `H5PL_term_interface':
H5PL.c:(.text+0x205): undefined reference to `dlclose'
/fs/posgrado16/other0/guido/libraries/hdf5/serial/lib/libhdf5.a(H5PL.o): In function `H5PL_load':
H5PL.c:(.text+0x477): undefined reference to `dlsym'
H5PL.c:(.text+0x5be): undefined reference to `dlopen'
H5PL.c:(.text+0x5d7): undefined reference to `dlsym'
H5PL.c:(.text+0x704): undefined reference to `dlclose'
H5PL.c:(.text+0x789): undefined reference to `dlerror'
H5PL.c:(.text+0x960): undefined reference to `dlclose'
collect2: error: ld returned 1 exit status
make: *** [h5_crtgrpar.exe] Error 1
I have no idea what the error is. Probably, there is something wrong with my Makefile.
To compile Fortran code with HDF5 enabled, you can replace
FC = gfortran
by
FC = h5fc
and skip all the hdf5 flags, as the h5fc wrapper will take care of those.
If you have some specific reason of calling the compiler by its name, you can learn about what flags are needed by calling
h5fc -show
that will show you what flags are added to the compiler.
On my computer (linux with gfortran), the result is:
gfortran -g -O2 -fstack-protector-strong -I/usr/include/hdf5/serial -L/usr/lib/x86_64-linux-gnu/hdf5/serial /usr/lib/x86_64-linux-gnu/hdf5/serial/libhdf5hl_fortran.a /usr/lib/x86_64-linux-gnu/hdf5/serial/libhdf5_hl.a /usr/lib/x86_64-linux-gnu/hdf5/serial/libhdf5_fortran.a /usr/lib/x86_64-linux-gnu/hdf5/serial/libhdf5.a -Wl,-z,relro -lpthread -lz -ldl -lm -Wl,-rpath -Wl,/usr/lib/x86_64-linux-gnu/hdf5/serial
Often you can get by with less flags than that, which you can find with some experimentation.
Given the error message you report, you lack the -ldl flags that enables linking of the dynamic linking library, see for isntance this other SO question.
I try to write a Makefile that takes several static libraries that have been created before and link the to an executable. Although one libary has a main-routine.
I get the error:
/lib/../lib64/crt1.o: In function `_start':
(.text+0x20): undefined reference to `main'
collect2: error: ld returned 1 exit status
make: *** [dockSIM_gcc_release] Error 1
I tried it with just linking the library that has the main routine but the error stays the same and comes directly after invoking make.
The Makefile:
SHELL = /bin/sh
RM=/bin/rm -f
CXX=g++
PROGNAME=dockSIM_gcc_release
DEFINES=-DDOCKSIM_VERBOSE=FALSE -DNDEBUG -DPRINT_LOG_MSG=0 -DPRINT_DEBUG_MSG=0
LDFLAGS = -fopenmp -g -O3 -std=c++11 -mavx -mstackrealign -fstrict-aliasing
LIBS= -lnagc_mkl -lm -L../externalCode -lpardiso500-GNU481-X86-64 -lacml
FILENAMES = commandInterpreter_lib.a
OBJNAMES =
all: $(PROGNAME)
$(PROGNAME): $(FILENAMES)
$(CXX) $(LDFLAGS) $(DEFINES) -o $(PROGNAME) $(FILENAMES)
clean:
$(RM) *.mo *.ho *.o $(PROGNAME) core *~
test:
echo $(FILENAMES)
showlibs:
echo $(LIBS)
The flags are compatible with those that were used to compile the code.
g++ 4.9.3 is used.
Signature of the main-Routine:
int main(int argc, char* argv[])
Thanks for help and kind regards.
I can only guess what's wrong.
There is more to linking a static library than just a convenient bundle of object files to reduce command line length. In addition to that, the linker only links in object files which it thinks are needed. An object file is needed if there's some undefined symbol that the linker is looking for, that is contained in that object. If there's no symbol that the linker needs in the object, then the linker ignores the object and doesn't link it.
The normal way to build a program is to have the main program listed as object files on the command line: the linker always links every object file. This gives the linker a set of symbols which are defined (by the object files) and undefined (things the object files use but that aren't defined by them). Then the linker will go through the libraries on the link line and add in object files that resolve undefined symbols. These object files in turn may have other undefined symbols that the linker will need to resolve later, etc.
All I can guess is that by not having any object files on your link line, the linker doesn't see the object file in the library containing main as needed and so it doesn't link it.
I don't know why building with debug vs. non-debug makes a difference.
I didn't understand your comment about why you need to do things this way: even if the person who knew about this left, someone will need to learn about it to maintain the software.
In any event you have a few options.
One simple one is to use the "ar" program to extract out the object file containing main and link it directly: in addition to adding objects to libraries ar can extract them. Then you can link that object directly. See the man page for ar.
Another would be to look at the documentation for your compiler and linker and find flags that will force it to include the entire library, not just the unresolved symbols in the library. For the GCC/binutils linker, for example, you can pass -Wl,--whole-archive before the libraries you want to be fully included on the command line, then -Wl,--no-whole-archive after them to turn off that feature.