CODEWITHSUNDEEP
c++compiler-errorsg++
dsollen
dsollen

Reputation: 29

g++ trying (failing) to link statically to libstdc++ for shared object

I'm trying to create a shared object using a number of .O files created with the -fPIC command. When I run g++ with the -shared argument it appears to be trying to statically link to the libstdc++.a library, which of course fails. I'm trying to figure out why it's automatically trying to link statically when I'm not using the -static-stdc++ argument.

when I try creating the shared object I get the error ...libstdc++.a(ios) relocate R_x86_64_325 against 'vtable for std::ios_base': cannot be used when making a shared object

I ran G++ with the -V argument and received and can see LD receives the argument -lstdc++.

Upvotes: 2

Views: 1392

Answers (2)

Mark B
Mark B

Reputation: 96233

I'll bet it's finding the static library first in its library search path, or ONLY finding the static library. Make sure that the appropriate version of the shared version is installed and can be found. You can probably truss your g++ run to hunt down the order in which it's opening libraries.

Upvotes: 0

PlasmaHH
PlasmaHH

Reputation: 16036

When linking together a single shared object, you need to do this from existing .o files. You can not do this from existing .so files; this would link those .so files to your .so file, but not into your .so file. So gcc seeks out and finds an archive of .o files (.a) and tries to link them. But since those are not compiled for relocation (no -fPIC), these can not be used to create .so files.

Your options are:

  • dynamically link your .so to the libstdc++ (and thus make it depending on the .so file that is installed in the system)
  • build .o files for libstdc++ and compile them with -fPIC then compile from those your .so file (here it does not matter if you use the .o files directly or an ar archive)

For the first (that I would recommend) option the following will suffice (it is from a makefile that I use for creating malloc/free intercepting .so files)

gcc -shared -lstdc++ -o your.so yourfiles.o

Upvotes: 3

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