I'm trying to compile a program provided to me. I noticed in the Makefile it runs the command
g++ -o test [...] -lpthread
I noticed the pthread library file is in /lib/libpthread.so.0 , but when I try to make the target, it gives me this error:
/usr/bin/ld: cannot find -lpthread
collect2: ld returned 1 exit status
how do I fix this?
In order to use -lpthread, you need a libpthread.a library archive and this is for static linking. libpthread.so.0 is a shared object which means it is used for dynamic linking. See GCC Link Options
Related
I'm interested in statically linking PROJ to a library created with pybind11.
but, I get error by cmake.
Why am I getting this error and how can I fix it?
My CMakeLists.txt is this.
cmake_minimum_required(VERSION 3.4)
project(myearth LANGUAGES CXX)
add_subdirectory(pybind11)
pybind11_add_module(myearth MyEarth.cpp)
include_directories(${CMAKE_SOURCE_DIR}/PROJ/include)
add_library(proj4 STATIC IMPORTED)
set_target_properties(proj4 PROPERTIES IMPORTED_LOCATION ${CMAKE_SOURCE_DIR}/PROJ/lib/libproj.a)
target_link_libraries(myearth PRIVATE proj4)
CMake Error.
I think fPIC option is for shared library. so, libproj.a is not necessary this option because this is static library.
(venv) ~/Projects/LinkLibTest/MySample/build$ make
[ 50%] Building CXX object CMakeFiles/myearth.dir/MyEarth.cpp.o
[100%] Linking CXX shared module myearth.cpython-36m-x86_64-linux-gnu.so
/usr/bin/ld: ../PROJ/lib/libproj.a(proj_4D_api.o): relocation R_X86_64_PC32 against symbol `pj_errno' can not be used when making a shared object; recompile with -fPIC
/usr/bin/ld: final link failed: bad value
collect2: error: ld returned 1 exit status
make[2]: *** [CMakeFiles/myearth.dir/build.make:98: myearth.cpython-36m-x86_64-linux-gnu.so] Error 1
make[1]: *** [CMakeFiles/Makefile2:100: CMakeFiles/myearth.dir/all] Error 2
make: *** [Makefile:91: all] Error 2
(venv) ~/Projects/LinkLibTest/MySample/build$
I created libproj.a by the following command.
$ ./configure --prefix=/output --disable-shared
$ sudo make
$ sudo make install
Linux Mint 20.3 64bit
CMake v3.22.2
PROJ v5.2.0 (https://proj.org/)
Python v3.6.8
Thank you.
Shared libraries must have position independent code, but your version of PROJ was built without it; you will have to rebuild PROJ with PIC.
$ ./configure --prefix=/output --with-pic
I am building an executable ("tool") on Linux. Using include $(GNUSTEP_MAKEFILES)/tool.make.
It's linked to a static lib that has also be build with GNUstep. The lib
contains Categories.
The executable builds fine but has errors at runtime not recognizing
methods defined in the static lib's Category:
Uncaught exception NSInvalidArgumentException, reason:
ClassNameOfClassTheCategoryExtends(instance) does not recognize
nameOfMethodInCategory
I am trying to fix that by passing -ObjC to the linker flags (also
tried -all_load) in the executable's GNUmakefile:
ADDITIONAL_LDFLAGS = -ObjC -all_load
But that seems to be ignored by clang. Here is the relevant output of
make install messages=yes debug=yes
clang: warning: argument unused during compilation: '-ObjC'
[-Wunused-command-line-argument]
clang: warning: argument unused during compilation: '-all_load'
[-Wunused-command-line-argument]
It looks like ADDITIONAL_LDFLAGS are used compiling, not linking.
Using this leads to the same result:
LDFLAGS := $(LDFLAGS) -ObjC
The excecutables GNUmakefileincludes the following:
include $(GNUSTEP_MAKEFILES)/common.make
# My make
include $(GNUSTEP_MAKEFILES)/tool.make
The resulting command line output is:
$ make install messages=yes debug=yes
This is gnustep-make 2.9.0. Type 'gmake print-gnustep-make-help' for help.
Running in gnustep-make version 2 strict mode.
Making all for tool NameOfExcecutable...
clang -ObjC -fuse-ld=/usr/bin/ld.gold -pthread -fexceptions -rdynamic -fobjc-runtime=gnustep-2.0 -fblocks -o obj/NameOfExcecutable \
./obj/NameOfExcecutable.obj/main.m.o ./obj/NameOfExcecutable.obj/MyClass.m.o ./obj/NameOfExcecutable.obj/StreamRunLoop.m.o ./obj/NameOfExcecutable.obj/Connector.m.o ./obj/NameOfExcecutable.obj/HTTPClient.m.o \
-L/home/user/GNUstep/Library/Libraries -L/usr/GNUstep/Local/Library/Libraries -L/usr/GNUstep/System/Library/Libraries -lgnustep-base -ldispatch -l/path/to/libOwnLib1.a -l/path/to/libOwnLib2.a -l/path/to/libOwnHavingTheCategories.a -l/path/to/libOwnLib4.a -l/path/to/libOwnLib5.a -luuid -lz -lpthread -ldl -lpthread -lobjc -lm
clang: warning: argument unused during compilation: '-ObjC' [-Wunused-command-line-argument]
Question:
What am I doing wrong
or
How can I work around the issue?
After digging into the issue of the linker not knowing the -ObjC flag (which we are used to use in Xcode) it looks like:
only ld.ld64 is aware of this flag
ld.ld64 is a (too genericly named) "linker for macOS" (from LLDB.org)
thus is not available for Linux linkers
To workaround we first stopped using GNUstep makefiles to
disable all GNUstep magic understand what is going on and wrote our own makefiles.
The actual fix to force link/load all .o files was to explicitly pass --whole-archive to the linker:
-Wl,-whole-archive path/to/static/lib/containing/categories/libOwnLib1.a -Wl,-no-whole-archive
I am using other people's makefile and get troubles when trying to compile a 'static' version of the exe
I have printed out the makefile's rules and the error is like this:
g++ Main.or System.or Options.or -Wall -lz --static -o main
/usr/bin/ld: cannot find -lz
/usr/bin/ld: cannot find -lstdc++
/usr/bin/ld: cannot find -lm
/usr/bin/ld: cannot find -lc
collect2: error: ld returned 1 exit status
If I do not include the '--static' option in the above command, it works fine.
The makefile also have rules to generate the static lib:
ar -rcsv lib_release.a Main.or System.or Options.or
r - Main.or
r - System.or
r - Options.or
Making Soft Link: lib_release.a -> lib.a
ln -sf lib_release.a lib.a
The -static linkage option instructs the linker to ignore all shared
libaries (libname.so) that could resolve the -lname linkage options (both explicit
and default) and accept only static libraries (libname.a). You have shared libraries installed on
your system that satisfy -lz, -lstdc++, -lm and -lc but no static ones.
For your linkage to work as it stands you must install the static libraries:
libz.a (Compression library)
libstdc++.a (The standard C++ library)
libm.a (The math library)
libc.a The standard C library
by the method that is appropriate to your distro.
I am new to g++ and lapack, and attempting to use them. I encountered a problem when I tried to compile the following naive code
#include <lapackpp.h>
int main()
{
LaGenMatDouble A;
return 0;
}
If I run the command
$g++ -L/usr/local/lib -llapackpp test2.cpp
where test2.cpp is the name of the cpp file, the terminal would give an error:
test2.cpp:1:22: fatal error: lapackpp.h: No such file or directory
But if I run the command:
$g++ -I/usr/local/include/lapackpp -L/usr/local/lib -llapackpp test2.cpp
the terminal would give an error:
/tmp/ccUi11DG.o: In function `main':
test2.cpp:(.text+0x12): undefined reference to `LaGenMatDouble::LaGenMatDouble()'
test2.cpp:(.text+0x23): undefined reference to `LaGenMatDouble::~LaGenMatDouble()'
collect2: ld returned 1 exit status
BTW, if I run the command
$pkg-config lapackpp --libs
the result is
-L/usr/local/lib -llapackpp
Could you please help me solve this? Thanks in advance!
Lapack requires fortran libraries, so that's where the -lgfortran comes from. Moreover, it appears the exact way to provide that library for the compiler depends on the Linux distriburion. From the documentation:
Requirements
This package requires the packages "blas", "lapack" (without the "++"), and a Fortran compiler. On most Linuxes these are available as pre-compiled binaries under the name "blas" and "lapack". For SuSE 10.x, the Fortran compiler is available as package "gfortran". For SuSE 9.x, the Fortran compiler is available as package "gcc-g77".
Not sure why pkg-config lapackpp --libs does not list -lgfortran
The -I/usr/local/include/lapackpp specifes the lapackpp-related header files. Without it the compiler cannot find lapackpp.h when you try to include it (#include <lapackpp.h>) -- see the compiler error in your question
I finally solved the problem but would still wonder why it has to be so.
The only command that can link cpp file to lapackpp library is:
g++ foo.cpp -o foo -lgfortran -llapackpp -I/usr/local/include/lapackpp
It would not work without -lgfortran, or with -I/usr/local/include/lapackpp replaced by -L/usr/local/lib.
Does anyone have an answer?
I was trying to compile a OpenCV's VideoCapture example. When I compile it, I get the following output:
gpp test.c
Info: resolving vtable for cv::VideoCapture by linking to __imp___ZTVN2cv12VideoCaptureE (auto-import)
c:/programs/mingw/bin/../lib/gcc/mingw32/4.5.0/../../../../mingw32/bin/ld.exe: warning: auto-importing has
enable-auto-import specified on the command line.
This should work unless it involves constant data structures referencing symbols from auto-imported DLLs.
(Btw, gpp is an alias to g++ -lhighgui -lcv -lcxcore)
So, I tried to compile with "gpp --enable-auto-import", but g++ didn't recognize this option. So, I tried to compile like this:
gpp -c test.c
ld test.o
And I've got the same error AND many other errors about STL functions, indicating it didn't link with STL:
undefined reference to std::cout
...
And, finally, when I compiled like this:
gpp -c test.c
ld --enable-auto-import test.o
This time, I've only got the STL errors. The VideoCapture error is gone! So I guess I solved this problem. The only thing is: how do I make ld link my program with STL libraries??????
Thanks in advance
The correct solution is build with
g++ test.c -lhighgui -lcv -lcxcore -Wl,--enable-auto-import
Unlike your 'gpp' alias, this puts libraries after objects which reference them (important when linking with archive libraries), and also properly passes --enable-auto-import flag to the linker.
Your current "fix" only works "by accident".