https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64390
Bug ID: 64390
Summary: "-shared" does not resolve symbols from lto generated
archives
Product: gcc
Version: 4.9.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: ipa
Assignee: unassigned at gcc dot gnu.org
Reporter: htl10 at users dot sourceforge.net
Upgrading to 4.9.2 from 4.8.x, building R (http://www.r-project.org) with fto
fails. ("./configure --enable-lto AR=gcc-ar").
Specifically, it builds a few static archives of external libraries then tries
build a shared libraries out of it. A simplified procedure is like this:
gcc -flto -c -o routine1.o routine1.c
...
gcc -flto -c -o used_by_routine1.o used_by_routine1.c
...
gcc-ar cr libextra.a used_by_routine1.o ...
...
gcc -shared -o liboutput.so routine1.o ... libextra.a ...
the output shared library is not able to resolve any symbols with libextra.a's
content.
I found two workarounds:
- putting all the dependent *.o on the command line instead of the archive
itself.
- prepending/appending the extra libraries with the whole archive linker
directives: i.e. "-Wl,--whole-archive ../extra/tre/libtre.a
-Wl,--no-whole-archive"
I realise generating shared libraries from static archive is daft, but that's
how R is built.
