I am trying to build a static executable of a C program which requires the following libraries from the Postgresql libecpg-dev package: libecpg, libpq, and libpgtypes. The static libraries, libecpg.a, libpq.a, libpgtypes.a, are all located in the same place as their dynamic versions, /usr/lib. I have tried adding the -L option as their path anyway, but I get the same result.
My executable needs to be static so that the binary can be portable so that users will not have to install the libraries onto their systems to use it. The program builds fine when I use the following command with the dynamic libraries: (The -I directory has to be included for some of the Postgresql functions I'm using)
gcc main.o -lecpg -lpq -lpgtypes -I/usr/include/postgresql -o program_name
When I try to link to the static libraries, I am using the following command:
gcc -static main.o -lecpg -lpq -lpgtypes -I/usr/include/postgresql -o program_name
The compiler, however, gives me a long list of "undefined reference" errors as output. There are so many, but here is a small sampling:
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../../lib/libecpg.a(descriptor.o):
In function `get_descriptors':
(.text+0xc3): undefined reference to `pthread_once'
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../../lib/libecpg.a(descriptor.o): In function `ECPGdeallocate_desc':
(.text+0x2c6): undefined reference to `pthread_setspecific'
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../../lib/libecpg.a(descriptor.o): In function `ECPGallocate_desc':
(.text+0x376): undefined reference to `pthread_setspecific'
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../../lib/libecpg.a(descriptor.o): In function `get_descriptors':
(.text+0xd2): undefined reference to `pthread_getspecific'
When I change the order as follows:
gcc -I/usr/include/postgresql -static -lecpg -lpq -lpgtypes -o program_name main.o
the compiler output instead looks like the following (once again, just a small sampling):
main.c:(.text+0x5c6): undefined reference to `ECPGconnect'
main.c:(.text+0x83e): undefined reference to `ECPGdo'
main.c:(.text+0x843): undefined reference to `ECPGget_sqlca'
main.c:(.text+0x85c): undefined reference to `ECPGdisconnect'
main.c:(.text+0x87c): undefined reference to `ECPGget_sqlca'
I have tried using the -I option all around (along with all of the other options), but nothing seems to work.
I think you just can't create a fully static non-trivial executable in modern Linux distribution anymore. But you can statically include some specific libraries.
Try it like that:
gcc main.o /usr/include/postgresql/libecpg.a /usr/include/postgresql/libecpg.a /usr/include/postgresql/libpq.a /usr/include/postgresql/libpgtypes.a -o program_name
Related
while I can use several turtle scripts in the same directory
(have eg. pretty.hs and srv.hs interpreted), I learned that I can have
only have one of them compiled eg. with
ghc -no-user-package-db -package-db .cabal-sandbox/*-packages.conf.d -O2 -threaded -outputdir=. -o srv srv.hs
as this implicitly builds Main.o and Main.hi as well, and and srv and pretty would
need two different object files, obviously.
What's the story of Turtle and the Main module anyway: wouldn't it
have been nicer, if one could use (and thus choose) a module name, like so
Module Whatever
import Turtle
I tried to compile the .o files separatly, but with no luck:
$ ghc -no-user-package-db -package-db .cabal-sandbox/*-packages.conf.d -O2 -threaded -outputdir=. -c -o MainPretty.o pretty.hs
no complaints so far, but then:
$ ghc -no-user-package-db -package-db .cabal-sandbox/*-packages.conf.d -O2 -threaded -outputdir=. -o pretty MainPretty.o
MainPretty.o: In function `rdyO_info':
(.text+0x40e): undefined reference to `transzuGZZTjP9K5WFq01xC9BAGQpF_ControlziMonadziIOziClass_zdfMonadIOIO_closure'
MainPretty.o: In function `rdyQ_info':
(.text+0x4d6): undefined reference to `transzuGZZTjP9K5WFq01xC9BAGQpF_ControlziMonadziIOziClass_zdfMonadIOIO_closure'
MainPretty.o: In function `cfxy_info':
(.text+0x712): undefined reference to `optpazuFpNJ7fLofFNEy3rK4ZZnBoD_OptionsziApplicativeziTypes_AltP_con_info'
MainPretty.o: In function `cfxy_info':
(.text+0x72e): undefined reference to `systezu0e3pMPmZZzzix21iFp2U03Lc_FilesystemziPathziRules_posixFromText_closure'
MainPretty.o: In function `cfyR_info':
(.text+0x92a): undefined reference to `optpazuFpNJ7fLofFNEy3rK4ZZnBoD_OptionsziApplicativeziTypes_AltP_con_info'
and so on...
Is it possible nevertheless to compile two different turtle scripts in the same dir? how?
Thanks.
Ah, to answer my own question: I saw that I just have to remove these Main.o/Main.hi files after compiling (to have different one created anew then),
like so:
ghc -no-user-package-db -package-db .cabal-sandbox/*-packages.conf.d -O2 -threaded -outputdir=. -o pretty pretty.hs
rm -f Main.o Main.hi
Sorry for the noise
I'm trying to link a library using mex from command line, or more exactly, from a makefile. I do this from a Makefile which I post here:
BDDM_MATLAB = #matlabhome#
MEXCC = $(BDDM_MATLAB)/bin/mex
MEXFLAGS = -v -largeArrayDims -O
MEXEXT = mexa64
TDIR = $(abs_top_srcdir)/test
IDIR = $(abs_top_srcdir)/src
LDIR = $(abs_top_srcdir)/lib
LOP1 = $(CUDA_LDFLAGS) $(LIBS)
SOURCES := $(wildcard *.cpp)
OBJS = $(SOURCES:.cpp=.o)
mTESTS = $(addprefix $(TDIR)/, $(SOURCES:.cpp=.$(MEXEXT)))
all: $(TDIR) $(mTESTS)
$(OBJS) : %.o : %.cpp
$(MEXCC) $(MEXFLAGS) -c -outdir ./ -output $# $(CUDA_CFLAGS) -I$(IDIR) CFLAGS="\$$CFLAGS -std=c99" $^
$(mTESTS) : $(TDIR)/%.$(MEXEXT) : %.o
$(MEXCC) $(MEXFLAGS) -L$(LDIR) -outdir $(TDIR) $^ $(LOP1) -lmpdcm LDFLAGS="-lcudart -lcuda"
.PHONY = $(TDIR)
$(TDIR):
$(MKDIR_P) $#
clean:
$(RM) *.o
libmpdcm is a static library that includes calls to two shared libraries libcuda and libcudart. My environment has
export LD_LIBRARY_PATH=/usr/local/cuda-7.0/lib64:$LD_LIBRARY_PATH:
My make rule produces
/usr/local/MATLAB/R2014a/bin/mex -v -largeArrayDims -O -L/home/eaponte/projects/test_cpp/lib -outdir /home/eaponte/projects/test_cpp/test test_LayeredEEG.o -L/usr/local/cuda/lib64 -lcudart -lcuda -lmpdcm LDFLAGS="-lcudart -lcuda"
This produces the following g++ command:
/usr/bin/gcc -lcudart -lcuda -shared -O -Wl,--version-script,"/usr/local/MATLAB/R2014a/extern/lib/glnxa64/mexFunction.map" test_LayeredEEG.o -lcudart -lcuda -lmpdcm -L/home/eaponte/projects/test_cpp/lib -L/usr/local/cuda/lib64 -L"/usr/local/MATLAB/R2014a/bin/glnxa64" -lmx -lmex -lmat -lm -lstdc++ -o /home/eaponte/projects/test_cpp/test/test_LayeredEEG.mexa64
The problem is that afterwards I get a linking error in Matlab:
Invalid MEX-file '/home/eaponte/projects/test_cpp/test/test_Fmri.mexa64': /home/eaponte/projects/test_cpp/test/test_Fmri.mexa64: undefined symbol: cudaFree
I know that the solution is simply to put the cuda libraries at the end of the g++ command
/usr/bin/gcc -lcudart -lcuda -shared -O -Wl,--version-script,"/usr/local/MATLAB/R2014a/extern/lib/glnxa64/mexFunction.map" test_LayeredEEG.o -lmpdcm -L/home/eaponte/projects/test_cpp/lib -L/usr/local/cuda/lib64 -L"/usr/local/MATLAB/R2014a/bin/glnxa64" -lmx -lmex -lmat -lm -lstdc++ -lcudart -lcuda -o /home/eaponte/projects/test_cpp/test/test_LayeredEEG.mexa64
How can achieve that running mex from command line (or from a Makefile)?
Just to illuminate the problem and solution and offer some help in avoiding the like:
The fundamental rule of linkage with the GNU linker
that your problem makefile transgressed is: In the commandline sequence of entities to be linked, ones that need symbol definitions
must appear before the ones that provide the definitions.
An object file (.o) in the linkage sequence will be incorporated entire in the output executable,
regardless of whether or not it defines any symbols that the executable uses. A library
on the other hand, is merely examined to see if it provides any definitions for symbols
that are thus-far undefined, and only such definitions as it provides are linked into in
the executable (I am simplifying somewhat). Thus, linkage doesn't get started until some object file is seen,
and any library must appear after everything that needs definitions from it.
Breaches of this principle usually arise from inept bundling of some linker flag-options
and some library-options together into a make-variable and its placement in the linkage recipe,
with the result that the bundled options are interpolated at a position that is valid for
the flags but not valid for libraries. This was so in your problem makefile, with LOP1 the
bad bundle.
In the typical case, the bundling causes all of the libraries to be placed before all the object files,
and never mentioned again. So the object files yield undefined symbol errors, because the libraries
they require were seen by the linker before it had discovered any undefined symbols, and were ignored.
In your untypical case, it resulted in libcudart and libcuda being seen later than your only
object file test_LayeredEEG.o - which however required no symbols from them - but earlier than
the only thing that did require symbols from them, the library libmpdcm. So they were ignored,
and you built a .mex64 shared library that had not been linked with them.
Long ago - pre-GCC 4.5 - shared libraries (like libcudart and libcuda) were exempt
from the requirement that they should be needed, at the point when the linker sees them,
in order to be linked. They were linked regardless, like object files, and the belief that
this is so has not entirely died out. It is not so. By default, shared libraries and
static libraries alike are linked if and only if needed-when-seen.
To avoid such traps it is vastly helpful to understand the canonical nomenclature of
the make variables involved in compilation and linkage and their semantics, and
their canonical use in compilation and linkage recipes for make. Mex is a
manipulator of C/C++/Fortran compilers that adds some commandline options of its own:
for make purposes, it is another compiler. For the options that it inherits from and
passes to the underlying compiler, you want to adhere to the usage for that compiler in make recipes.
These are the make variables most likely to matter to you and their meanings:
CC = Your C compiler, e.g. gcc
FC = Your Fortran compiler, e.g. gfortran
CXX = Your C++ compiler, e.g. g++.
LD = Your linker, e.g. ld. But you should know that only for specialized uses
should the linker be directly invoked. Normally, the real linker is invoked on your
behalf by the compiler. It can deduce from the options that you pass it whether you
want compiling done or linking done, and will invoke the appropriate tool. When you
want linking done, it will quietly augment the linker options that you pass with
additional ones that it would be very tiresome to specify, but which ensure
that the linkage acquires all the the correct flags and libraries for the language of the
program you are linking. Consequently almost always, specify your compiler as your
linker.
AR = Your archiving tool (static library builder)
CFLAGS = Options for C compilation
FFLAGS = Options for Fortran compilation
CXXFLAGS = Options for C++ compilation
CPPFLAGS = Options for the C preprocessor, for any compiler that uses it. Avoid the common mistake of writing CPPFLAGS when you mean CXXFLAGS
LDFLAGS = Options for linkage, N.B. excluding library options, -l<name>
LDLIBS = Library options for linkage, -l<name>
And the canonical make rules for compiling and linking:
C source file $< to object file $#:
$(CC) $(CPPFLAGS) $(CFLAGS) -c $# $<
Free-from Fortran file $< to object file $#, with preprocessing:
$(FC) $(CPPFLAGS) $(FFLAGS) -c $# $<
(without preprocessing, remove $(CPPFLAGS))
C++ source file $< to object file $#:
$(CXX) $(CPPFLAGS) $(CXXFLAGS) -c $# $<
Linking object files $^ into an executable $#:
$(<compiler>) $(LDFLAGS) -o $# $^ $(LDLIBS)
If you can as much as possible write makefiles so that a) you have assigned the right options to the right variables from
this glossary, and b) used the canonical make recipes, then your path will be much smoother.
And BTW...
Your makefile has the following bug:
.PHONY = $(TDIR)
This is apparently an attempt to make $(TDIR) a phony target,
but the syntax is wrong. It should be:
.PHONY: $(TDIR)
what the assignment does is simply create a make variable called, .PHONY with the value of $(TDIR),
and does not make $(TDIR) a phony target.
Which is fortunate, because $(TDIR) is your output directory and not a phony
target.
You wish to ensure that make creates $(TDIR) before you need to output anything into
it, but you do not want it to a normal prequisite of those artefacts, which would oblige
make to rebuild them whenever the timestamp of $(TDIR) was touched. That is presumably
why you thought to make it a phony target.
What you actually want $(TDIR) to be is an order-only prerequsite
of the $(mTESTS) that will be output there. The way to do that is to amend the $(mTESTS) rule to be:
$(mTESTS) : $(TDIR)/%.$(MEXEXT) : %.o | $(TDIR)
This will cause $(TDIR) to be made, if needed, before $(mTESTS) is made, but
nevertheless $(TDIR) will not be considered in determining whether $(mTESTS) does
need to be made.
On the other hand, the targets all and clean are phony targets: no such artefacts
are to be made, so you should tell make so with:
.PHONY: all clean
As pointed out in the comments, the problem was in the order of the dynamic libraries in the compilation flags. After searching the reason for this I found in SO that static libraries need to be linked taking into account the order of dependency. In my case, the library libmpdc had dependencies on libcuda and libcudart but was on the left. The solution is to swap the order in the makefile from:
$(mTESTS) : $(TDIR)/%.$(MEXEXT) : %.o
$(MEXCC) $(MEXFLAGS) -L$(LDIR) -outdir $(TDIR) $^ $(LOP1) -lmpdcm LDFLAGS="-lcudart -lcuda"
to
$(mTESTS) : $(TDIR)/%.$(MEXEXT) : %.o
$(MEXCC) $(MEXFLAGS) -L$(LDIR) -outdir $(TDIR) $^ -lmpdcm $(LOP1)
This question already has an answer here:
Reading data from matlab files into C
(1 answer)
Closed 7 years ago.
I have to import a MAT-file in a fortran program. I followed the example file but I am facing some problems while linking. The compilation happens fine.
Minimal code:
#include "fintrf.h"
PROGRAM main
USE ssa
USE dmotifs
USE param
IMPLICIT NONE
! MAT-FILE Declarations !
INTEGER matOpen, matGetDir
INTEGER matGetVariableInfo
INTEGER mp, dir, adir(100), pa
INTEGER mxGetM, mxGetN, matClose
INTEGER ndir, i, clstat
CHARACTER*32 names(100)
!===========================!
if(all(fnames(:)%fn .NE. argfun)) then
write(*,*) "No such motif: ",argfun
write(*,*) "Input format-> main <motifname>"
stop
else
fin=fchton(argfun)
y0=nM2m*analys(p,argfun)
! ==> OPEN MAT-file <== !
mp=matOpen('./PRMS_lxr_29Apr15.mat','r')
if (mp .eq. 0) then
write(6,*) "Can't open MAT-file"
stop
end if
dir = matgetdir(mp, ndir)
if (dir .eq. 0) then
write(6,*) "Can't read MAT-file-directory."
stop
endif
call mxCopyPtrToPtrArray(dir, adir, ndir)
do 20 i=1,ndir
call mxCopyPtrToCharacter(adir(i), names(i), 32)
20 continue
write(6,*) 'Directory of Mat-file:'
do 30 i=1,ndir
write(6,*) names(i)
30 continue
write(6,*) 'Getting Header info from first array.'
pa = matGetVariableInfo(mp, names(1))
write(6,*) 'Retrieved ', names(1)
write(6,*) ' With size ', mxGetM(pa), '-by-', mxGetN(pa)
call mxDestroyArray(pa)
clstat=matClose(mp)
end if
END PROGRAM main
I am using gfortran 4.8.3 for compiling+linking using the default command:
gfortran main.f90 dmotifs.o param.o ssa.o -o main
This code compiles fine (without linking) when I do not include: #include "finitrf.h", otherwise the compiler says
Warning: main.f90:1: Illegal preprocessor directive
I tried renaming finitrf.h to finitrf.f90 but it did not make any difference. Nonetheless during linking I am getting these errors:
main.f90:(.text+0x3ea): undefined reference to `matopen_'
main.f90:(.text+0x487): undefined reference to `matgetdir_'
main.f90:(.text+0x52b): undefined reference to `mxcopyptrtoptrarray_'
main.f90:(.text+0x583): undefined reference to `mxcopyptrtocharacter_'
main.f90:(.text+0x71b): undefined reference to `matgetvariableinfo_'
main.f90:(.text+0x804): undefined reference to `mxgetm_'
main.f90:(.text+0x855): undefined reference to `mxgetn_'
main.f90:(.text+0x89c): undefined reference to `mxdestroyarray_'
main.f90:(.text+0x8b0): undefined reference to `matclose_'
collect2: error: ld returned 1 exit status
Do I need a makefile or add additional arguments in the compile command?
EDIT:
I added the -cpp option and that eliminates the problem of Illegal preprocessor directive
Now when I am compiling with paths to matlab external components (where finitf.h) is, I am still getting the same error.
gfortran main.f90 dmotifs.o param.o ssa.o -I/usr/local/matlab2008a/extern/include -L/usr/local/matlab2008a/extern/lib -cpp -o main
If I provide library path to /usr/local/matlab2008a/bin/glnxa64 that contains other matlab libraries including libmat.so, I still get the same errors.
For lower case file extensions *.f90 or *.f the pre-processor is typically deactivated. To enable that, either rename the (main) file to have a capital extension *.F90 or *.F, or provide the corresponding command-line option (-cpp for gfortran, -fpp for ifort).
Assuming the missing subroutines/functions are actually declared in fintrf.h, this should solve your problem.
You should additionally tell the compiler to link against the libraries containing the Matlab functions.
As pointed out by Alexander Vogt, the compiler requires -cpp option for the pre-processor to recognize the header file and not to treat it as illegal.
Linking requires finitrf.h which is usually located in the <matlabroot>/extern/include and the essential libraries are present in <matlabroot>/bin/<arch>/.
But just specifying this does not work and specification of the exact matlab library seems essential; these are libmat.so and libmx.so.
These libraries are in turn dependent on other libraries so another flag is required to set the rpath.
Finally it works with following command:
gfortran main.f90 dmotifs.o param.o ssa.o -I/usr/local/matlab2008a/extern/include -L/usr/local/matlab2008a/bin/glnxa64 -cpp -o main -lmat -lmx -Wl,-rpath /usr/local/matlab2008a/bin/glnxa64/
or in general
gfortran program.f90 -I<matlabroot>/extern/include -L<matlabroot>/bin/<arch> -cpp -lmat -lmx -Wl, -rpath <matlabroot>/bin/<arch> -o program.out
Also see this post that is about the same problem in C.
I am beginner in Iphone programming. I am trying to compile (ubuntu).
#import <Foundation/Foundation.h>
int main (void)
{
NSLog (#"Executing");
return 0;
}
I compiled it but getting following error
subhash#subhash-Lenovo-G570:~/grit/iphone/mac$ gcc -lgnustep-base -lpthread -lob
jc -lm -I/usr/local/include/GNUstep -I/usr/include/GNUstep -fconstant-string-cla
ss=NSConstantString hello.m -o hello
In file included from /usr/include/GNUstep/Foundation/NSClassDescription.h:30:0,
from /usr/include/GNUstep/Foundation/Foundation.h:50,
from hello.m:1:
/usr/include/GNUstep/Foundation/NSException.h:42:2: error: #error The current se
tting for native-objc-exceptions does not match that of gnustep-base ... please
correct this.
i followed the http://ubuntuforums.org/showthread.php?p=5593608 as a reference.
I commented #error directive of NSException.h and problem is solved. Now i am getting new error.
/tmp/ccQlI9wJ.o: In function `main':
hello.m:(.text+0x11): undefined reference to `NSLog'
/tmp/ccQlI9wJ.o: In function `__objc_gnu_init':
hello.m:(.text+0x2a): undefined reference to `__objc_exec_class'
/tmp/ccQlI9wJ.o:(.data+0x40): undefined reference to `__objc_class_name_NSConsta
ntString'
collect2: ld returned 1 exit status
in Compile Objective-C Programs Using gcc
there is the following
Also note that if you did not include -D_NATIVE_OBJC_EXCEPTIONS, you
may run into the following error:
/usr/include/GNUstep/Foundation/NSException.h:42:2: error: #error The
current setting for native-objc-exceptions does not match that of
gnustep-base ... please correct this.
I has the same error as the original poster did, and passing the -D_NATIVE_OBJC_EXCEPTIONS flag fixed the problem for me.
I was trying to do something pretty non-standard, so it might not work for everyone.
Note that shalki's answer may also fix the issue. In case the link referenced there vanishes,
the blog post in question,
Compile Objective-C Programs on Linux
is in Chinese or Japanese or something like that, so I don't know exactly what it is saying, but I think the upshot is
to pass
`gnustep-config --objc-flags`
as an argument to gcc. The post has
gcc `gnustep-config --objc-flags` hello.m -o hello -I /usr/include/GNUstep/ -L /usr/lib/GNUstep/ -lgnustep-base
at the end. Now, on my machine, gnustep-config --objc-flags expands to
-MMD -MP -DGNUSTEP -DGNUSTEP_BASE_LIBRARY=1 -DGNU_GUI_LIBRARY=1 -DGNU_RUNTIME=1 -DGNUSTEP_BASE_LIBRARY=1 -D_REENTRANT -fPIC -Wall -DGSWARN -DGSDIAGNOSE -Wno-import -g -O2 -fno-strict-aliasing -fexceptions -fobjc-exceptions -D_NATIVE_OBJC_EXCEPTIONS -fgnu-runtime -fconstant-string-class=NSConstantString -I. -I/home/faheem/GNUstep/Library/Headers -I/usr/local/include/GNUstep -I/usr/include/GNUstep
Yowza. Notice that this list of flags does contain-D_NATIVE_OBJC_EXCEPTIONS, along with lots of other stuff. For the record, my machine is running Debian squeeze. This might be a Debian/Ubuntu specific problem. I'm not sure.
Better write a GNUmakefile.
http://www.gnustep.it/nicola/Tutorials/WritingMakefiles/index.html
And better stop using gcc and switch to clang.
First off: I looked at the related questions, but they are not very helpful unfortunately. I'm trying to wrap an enum and a class from an external library.
#include <Python.h>
#include <boost/python.hpp>
using namespace boost::python;
#include <libvpsc/rectangle.h>
using vpsc::Rectangle;
using vpsc::Dim;
BOOST_PYTHON_MODULE(adaptagrams)
{
enum_<Dim>("dim")
.value("x", vpsc::XDIM)
.value("y", vpsc::YDIM)
.value("unset", vpsc::UNSET)
;
class_<Rectangle>("Rectangle",
init<double, double, double, double, optional<bool> >())
.add_property("centerX", &Rectangle::getCentreX)
.add_property("centerY", &Rectangle::getCentreY)
.add_property("width", &Rectangle::width, &Rectangle::set_width)
.add_property("height", &Rectangle::height, &Rectangle::set_height)
;
}
and compile with:
g++ -fPIC -I/usr/include/python2.7 -c adaptagrams.cpp -o adaptagrams.o
g++ -shared -Wl,-soname,adaptagrams.so -o adaptagrams.so adaptagrams.o -lpython2.7 -lboost_python -lvpsc
However, when I try to import the .so module, I get an error:
ImportError: dynamic module does not define init function (PyInit_adaptagrams)
Any ideas?
Update: When I restart Python and try the import, the first error I get is:
ImportError: ./adaptagrams.so: undefined symbol: _ZN8topology13computeStressERKSt6vectorIPNS_4EdgeESaIS2_EE
When I try it again, the 2nd one is the dynamic import from above (2.7) and a segfault (3.2). Boost is compiled against both 2.7 and 3.2 and I am linking the right ones on each approach.
Update 2: The tutorial code from the boost_python page works:
#include <Python.h>
#include <boost/python.hpp>
using namespace boost::python;
struct Hello
{
Hello(std::string msg): msg(msg) {}
void set(std::string msg) { this->msg = msg; }
std::string greet() { return msg; }
std::string msg;
};
BOOST_PYTHON_MODULE(constructor)
{
class_<Hello>("Hello", init<std::string>())
.def("greet", &Hello::greet)
.def("set", &Hello::set)
;
}
Same compilation:
g++ -fPIC -I/usr/include/python2.7 -c constructor.cpp -o constructor.o
g++ -shared -Wl,-soname,constructor.so -o constructor.so constructor.o -lpython2.7 -lboost_python
The name used in BOOST_PYTHON_MODULE must match the name of the .so library you generate and import into python.
I have seen this exception before. I got it using Visual Studio on windows, so things might be a little different over in unix-oid land but:
Two Possibilities:
Debug/Release miss-match:
You are trying to import a debug build of your module into a release build of python (or vice-versa). The solution is to include boost/python/detail/wrap_python.hpp instead of Python.h. This will fix some includes and defines to make it possible to do what you want.
Python/Boost.Python version miss-match:
Boost.Python is compiled against one specific version of python. You are using it with a different version. For example: you seem to be using python 2.7. Your boost_python library might be compiled against python 2.6. Yes, this means that your module can only work with one version of python at a time.
In addition to the other answers (in case another unfortunate soul runs unto this), make sure you're not accidentally compiling with the -fvisibility=hidden flag.
Doing so seems to strip the init function from the binary in both g++ / clang++.
Background info
In my case I had some trouble integrating some wrappers made with Boost.Python into a project. When built with the project's build-system I'd get the same runtime-error as OP (as opposed to building it with my proof-of-concept Makefile where it worked just fine).
Comparing the symbol tables with nm -g foo.so | grep Py showed me that in the non-working case the PyInit_* function was completely absent. Doing some comparison between compilation flags led me to -fvisibilty=hidden being the culprit.