When compiling code examples from a textbook, I run into a compilation error: ld: library not found for -lstdc++fs. What does this error mean and how can I get around it?
% make filesystem
Consolidate compiler generated dependencies of target filesystem
[100%] Linking CXX executable filesystem
ld: library not found for -lstdc++fs
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[3]: *** [chapter_17/filesystem] Error 1
make[2]: *** [chapter_17/CMakeFiles/filesystem.dir/all] Error 2
make[1]: *** [chapter_17/CMakeFiles/filesystem.dir/rule] Error 2
make: *** [filesystem] Error 2
In short, linking stdc++fs is not longer necessary as it has been incorporated into the base library.
When the textbook was first written the C++ libraries didn't officially support filesystem yet, so they would require a secondary library called stdc++fs. This was a libstdc++ specific library that imported the C++17 features that weren't in the official library yet.
Now, both GCC's libstdc++ and Clang's libc++ include it in their base library, and the stdc++fs library got dropped.
You can drop the linking to that library without any problems; it patched a problem in compiler support that's no longer relevant
Related
I am trying to build a C++ library(https://github.com/ipkn/crow) on macOS 12.0.1(Monterey).
Since I am learning C++ since yesterday, I have no clue what to do next with error message like this:
ld: warning: dylib (/usr/local/lib/libboost_system-mt.dylib) was built for newer macOS version (12.0) than being linked (11.3)
ld: warning: dylib (/usr/local/lib/libboost_thread-mt.dylib) was built for newer macOS version (12.0) than being linked (11.3)
[ 19%] Built target example_chat
Consolidate compiler generated dependencies of target example_ssl
[ 23%] Building CXX object examples/CMakeFiles/example_ssl.dir/ssl/example_ssl.cpp.o
make[2]: *** No rule to make target `/usr/bin/openssl/lib', needed by `examples/example_ssl'. Stop.
make[1]: *** [examples/CMakeFiles/example_ssl.dir/all] Error 2
make: *** [all] Error 2
/usr/bin/openssl is actually the result when which openssl is executed
My question: As a toddler in C++, how to debug an error message like this? What I have to learn as prerequisites ?
My goal is to compile my C program to wasm with emscripten (which I installed via emsdk). It uses libxml2. I am following the steps outlined here https://github.com/kripken/xml.js/blob/master/script/libxml2 to build
libxml2 from source with the appropriate emscripten parameters.
When I run emmake make, I get the following warnings and errors:
...
CCLD libxml2.la
emcc: warning: linking a library with `-shared` will emit a static object file.
This is a form of emulation to support existing build systems.
If you want to build a runtime shared library use the SIDE_MODULE setting. [-Wemcc]
emcc: warning: ignoring unsupported linker flag: `--version-script=./libxml2.syms` [-Wlinkflags]
wasm-ld: error: cannot open libxml2.so.2: No such file or directory
emcc: error: '/home/willy/emsdk/upstream/bin/wasm-ld -o .libs/libxml2.so.2.9.9 .libs/SAX.o .libs/entities.o .libs/encoding.o -L/home/willy/emsdk/upstream/emscripten/system/local/lib .libs/error.o -L/home/willy/emsdk/upstream/emscripten/system/lib .libs/parserInternals.o -L/home/willy/emsdk/upstream/emscripten/cache/wasm .libs/parser.o .libs/tree.o .libs/hash.o .libs/list.o .libs/xmlIO.o .libs/xmlmemory.o .libs/uri.o .libs/valid.o .libs/xlink.o .libs/HTMLparser.o .libs/HTMLtree.o .libs/debugXML.o .libs/xpath.o .libs/xpointer.o .libs/xinclude.o .libs/nanohttp.o .libs/nanoftp.o .libs/catalog.o .libs/globals.o .libs/threads.o .libs/c14n.o .libs/xmlstring.o .libs/buf.o .libs/xmlregexp.o .libs/xmlschemas.o .libs/xmlschemastypes.o .libs/xmlunicode.o .libs/xmlreader.o .libs/relaxng.o .libs/dict.o .libs/SAX2.o .libs/xmlwriter.o .libs/legacy.o .libs/chvalid.o .libs/pattern.o .libs/xmlsave.o .libs/xmlmodule.o .libs/schematron.o .libs/xzlib.o /home/willy/emsdk/upstream/emscripten/cache/wasm/libc.a libxml2.so.2 --relocatable -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr' failed (1)
make[2]: *** [Makefile:1065: libxml2.la] Error 1
make[2]: Leaving directory '/home/willy/CWasmSandbox/libxml2-2.9.9'
make[1]: *** [Makefile:1484: all-recursive] Error 1
make[1]: Leaving directory '/home/willy/CWasmSandbox/libxml2-2.9.9'
make: *** [Makefile:897: all] Error 2
The only thing I can gather with my limited understanding of emscripten is that it tries to access libxml2.so.2 which under normal circumstances would be generated from libxml2.la. But libxml2.so.2 was not generated because emscripten does not produce shared objects. Is this assesment correct? I tried passing the option CFLAGS="-s SIDE_MODULE=1" to make, but it didn't fix the error and was probably a stupid idea born from my limited knowledge of build systems. I also tried copying libxml2.so.2 from a previous installation into the appropriate directory, but no luck, and also kind of dumb since emscripten would have no use for .so files? What should my next steps be?
Easiest way is to resign from shared lib.
There is an important limitation with shared one (side module): it will not work if you are going to use threads in your main application.
So just make a change of ./script/libxml2
-emconfigure ../libxml2/configure --with-http=no --with-ftp=no --with-python=no --with-threads=no
+emconfigure ../libxml2/configure --with-http=no --with-ftp=no --with-python=no --with-threads=no --enable-shared=no
Build and link ./build/.libs/libxml2.a with your main application.
I am trying to run a project that was made and works for Ubuntu but on Mac OS. And when I am doing the make I got the following error:
ld: library not found for -lrt
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[2]: *** [consumer] Error 1
make[1]: *** [CMakeFiles/consumer.dir/all] Error 2
make: *** [all] Error 2
I can't see any library with that name at thole project.
Can anyone explain what it is and how to solve it?
On old Linux systems, several functions, such as clock_gettime, are documented to need -lrt for old versions of GNU libc. This is no more the case on recent glibc (after 2.17 from 2013).
So you can remove -lrt from your Makefile (and remove the thing from your cmake configuration thing generating it).
BTW, removing -lrt should also fit for recent Linux distributions.
PS. If you are paying support for your Linux system, you should ask your support for advice.
While compiling a project i get the following error as
c:/mingw/bin/../lib/gcc/mingw32/4.6.2/../../../../mingw32/bin/ld.exe: cannot find lwxmsw28
collect2: ld returned 1 exit status
make[2]: *** [dist/Debug/MinGW-Windows/libRegistration.dll] Error 1
make[1]: *** [.build-conf] Error 2
make: *** [.build-impl] Error 2
I am using wxwidgets libraries however when i ran a command in cmd as
wx-config --libs
i could not see lwxmsw28 either let me know if it is downloadable from somewhere or any workaround to resolve this issue.
Thanks
This is a linker error, rather than a compilation error.
"lwxmsw28" looks to me like a wxwidgets v2.8 microsoft windows library. Should the linker be looking for this? Since you are using mingw, I would think you should NOT be linking to msw libraries. However, I am not familiar with mingw, so maybe this is the name used for mingw libraries.
If this is the correct library, then the next question is: have you built the wxWidgets libraries? The libraries are NOT "downloadable from somewhere" - you must download the source and build the libraries yourself.
A simple test to find out if you have built the libraries - try to build one of the sample projects.
I'm cross compiling to an arm embedded system and receiving an error that I have questions about. Here is the error:
[ 19%] Built target cxjpeg-6b
Linking CXX shared library /home/botbear/JAUS++-2.110519- src/libraries/jaus++/2.0/lib/libcxutils.so
/home/botbear/openwrt/trunk/staging_dir/toolchain-arm_v6k_gcc-linaro_uClibc- 0.9.32_eabi/lib/gcc/arm-openwrt-linux-uclibcgnueabi/4.5.4/../../../../arm-openwrt-linux- uclibcgnueabi/bin/ld: cannot find -lpng
collect2: ld returned 1 exit status
make[2]: *** [/home/botbear/JAUS++-2.110519-src/libraries/jaus++/2.0/lib/libcxutils.so] Error 1
make[1]: *** [libcxutils/CxUtils/libcxutils/CMakeFiles/cxutils.dir/all] Error 2
make: *** [all] Error 2
As you can see the linker is looking for a static library named 'libpng'. In addition to the libpng lib., the command in the sub-make file using the -l switch to link to the following libraries: -lpng -lz -lX11 -lXtst -lpthread -Wl. All of the libraries (libpng,libz,libX11, etc) are in my host /usr/lib/ directory but my target toolchain does not have the the libraries. My question is if I manually recompile the libraries with my target compiler will that solved my problem? Or I'm going to have find and install packages for each of the libraries for my target platform.
Thanks in advance.
You seem to compile for the target, so you need target libraries. Either compiled by yourself or provided by the toolchain development environment (if you have one). The latter usually saves you some headaches (cross compiling and setting the paths where necessary).
I see you are using openwrt toolchain. Openwrt seems to have libpng as a package. I'd go with that if possible.