libstdc++ DSO missing

Hi,

I intergrated my application to buildroot. Complie is successfull by when linking I get errors:

x86_64-buildroot-linux-gnu/sysroot/usr/lib64/libstdc++.so.6: error adding symbols: DSO missing from command line

Are libraries missing from buildroot environment?

Additional I get warnings that some .so files not found, but they are available in output/build/<Tool>/lib

But I included this path by $(@D)/../<Tool>/lib

Quoted 7 lines

Hi,

I intergrated my application to buildroot. Complie is successfull by when linking I get errors:

x86_64-buildroot-linux-gnu/sysroot/usr/lib64/libstdc++.so.6: error adding symbols: DSO missing from command line

This error means that:
- the linker found a library with a DT_NEEDED dependency on libstdc++.so.6
- the linker found libstdc++.so.6
- the linker is missing symbols
- the linker found the missing symbols in libstdc++.so.6
- but the linker command line does not include libstdc++.so.6
- so the linker is not sure if the user actually intended to link with libstdc++.so.6.
- so it refuses to link.

Since libstdc++.so.6 is the C++ runtime library, this either mean that:
- you are linking a C++ program with ld or gcc instead of g++

- you are linking a C program with a C++ library that requires libstdc++.so.6, in this case you may need -lstdc++ on the linker command line.

Quoted 1 line

Are libraries missing from buildroot environment?

No, only the linker command line is incorrect.

Quoted 2 lines

Additional I get warnings that some .so files not found, but they are available in output/build/<Tool>/lib

The compiler will only search libraries in output/staging/lib or output/staging/usr/lib.
The package for <Tool> should install the libraries there, so that other programs can link with them. This is done by putting

<TOOL>_INSTALL_STAGING = YES

in its .mk file.  If <Tool> is a generic-package (and not a autotools/meson/cmake package), then you also need to manually explain how to install libraries to $(STAGING_DIR)/lib:

https://nightly.buildroot.org/manual.html#_infrastructure_for_packages_with_specific_build_systems

Quoted 1 line

But I included this path by $(@D)/../<Tool>/lib

While it may work, this is a kludge.

Thank you for your detailed explanation.

Quoted 20 lines · Alex

Quoted 7 lines

Hi,

I intergrated my application to buildroot. Complie is successfull by when linking I get errors:

x86_64-buildroot-linux-gnu/sysroot/usr/lib64/libstdc++.so.6: error adding symbols: DSO missing from command line

This error means that:
- the linker found a library with a DT_NEEDED dependency on libstdc++.so.6
- the linker found libstdc++.so.6
- the linker is missing symbols
- the linker found the missing symbols in libstdc++.so.6
- but the linker command line does not include libstdc++.so.6
- so the linker is not sure if the user actually intended to link with libstdc++.so.6.
- so it refuses to link.

Quoted 3 lines

Since libstdc++.so.6 is the C++ runtime library, this either mean that:
- you are linking a C++ program with ld or gcc instead of g++

Yap, outside of buildroot, linking calls the g++ but when linking inside buildroot,  calls the x86_64-buildroot-linux-gnu-ld, because $(LD) in the makefile is set to x86_64-buildroot-linux-gnu-ld within buildroot.

Inside the package .mk file of the BUILD_CMDS calls make:

$(MAKE) $(TARGET_CONFIGURE_OPTS)  -C $(@D)

So (a kludge to test), i replaced in the Makefile
$(LD)
by
$(HOST_DIR)/bin/x86_64-linux-g++
Now linking is successfull...
Is there a more "elegant" way to do this...? Not so a kludge like that, mean setting this within the mk file before calling the projekt make... And how to specifey $(CC) also to g++??

Quoted 18 lines

- you are linking a C program with a C++ library that requires libstdc++.so.6, in this case you may need -lstdc++ on the linker command line.

Quoted 1 line

Are libraries missing from buildroot environment?

No, only the linker command line is incorrect.

Quoted 2 lines

Additional I get warnings that some .so files not found, but they are available in output/build/<Tool>/lib

The compiler will only search libraries in output/staging/lib or output/staging/usr/lib.
The package for <Tool> should install the libraries there, so that other programs can link with them. This is done by putting

<TOOL>_INSTALL_STAGING = YES

Quoted 3 lines

in its .mk file.  If <Tool> is a generic-package (and not a autotools/meson/cmake package), then you also need to manually explain how to install libraries to $(STAGING_DIR)/lib:

Indeed I forgot one of the .so to be  installed to staging. After adding this and append to the $(MAKE) call the LD_LIBRARY_PATH="$(@D)../<Tool>/lib" compile and linking is successfull.

Quoted 7 lines

https://nightly.buildroot.org/manual.html#_infrastructure_for_packages_with_specific_build_systems

Quoted 1 line

But I included this path by $(@D)/../<Tool>/lib

While it may work, this is a kludge.

make doesn't seem to have a built in rule for linking C++