Building uClibc++

Warning

Migrated from: https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=139629550 and is probably outdated

A version of uClibc++ has been ported to NuttX and is available in the NuttX uClibc++ GIT repository at Bitbucket.org . This version of uClibc++ was adapted for NuttX by the RGMP team.

This custom version of uClibc++ resides in the NuttX repository at:

rather than in the main NuttX source tree, due to licensing issues: NuttX is licensed under the permissive, modified BSD License; uClibc++, on the other hand, is licensed under the stricter GNU LGPL Version 3 license.

General build instructions are available in the uClibc++ README.txt file. Those instructions are not repeated here. This page documents specific issues encountered when building this NuttX version of uClibc++ and how they are resolved.

Undefined Reference to _impure_ptr

Problem

When building uClibc++, you may encounter an undefined reference to _impure_ptr similar to:

LD: nuttx
.../arm-none-eabi/lib/armv7e-m\libsupc++.a(vterminate.o): In function
`__gnu_cxx::__verbose_terminate_handler()`:
vterminate.cc:(.text._ZN9__gnu_cxx27__verbose_terminate_handlerEv+0xfc):
undefined reference to `_impure_ptr'

Solution

A definitive, elegant solution is not known, but the following workaround has proven to work:

  1. Locate the directory where you can find libsupc++:

    arm-none-eabi-gcc -mcpu=cortex-m4 -mthumb -print-file-name=libsupc++.a

  2. Go to that directory and save a copy of vterminate.o (in case you need it later):

    cd <the-directory-containing-libsupc++.a>
arm-none-eabi-ar.exe -x libsupc++.a vterminate.o

  3. Remove vterminate.o from the library. At build time, the uClibc++ package will provide a usable replacement:

    arm-none-eabi-ar.exe -d libsupc++.a vterminate.o

  4. At this point, NuttX should link with no problem. If you ever want to restore the original vterminate.o to libsupc++.a, you can do so by running:

    arm-none-eabi-ar.exe rcs libsupc++.a vterminate.o

After removing vterminate.o from the standard library, the uClibc++-provided vterminate.o becomes the active implementation and prevents references to _impure_ptr from arising during linkage.

Note

Always exercise caution when modifying toolchain libraries. This workaround is known to be effective but it replaces standard library objects, which may have side effects in other toolchain usage scenarios.