When I try to use protected function pointers in a shared library, I experience
strange behaviour: directly passing a function name triggers an invalid
relocation during linking stage while it works when assigning the function name
to a global variable first.
This report might be a duplicate to the old bug 19520, but I'm not sure as my
knowledge about ELF internals is rather limited and I don't understand most of
the discussion there, sorry. If this is a duplicate, please excuse.
Here's the output during compilation. Sources will follow in a few seconds:
$ LANG="" gcc -v -save-temps -Wall test2.c -o libtest2.so -shared -fPIC
-fvisibility=hidden
Using built-in specs.
Target: i686-pc-linux-gnu
Configured with: ./configure --enable-languages=c,c++
Thread model: posix
gcc version 4.3.2 (GCC)
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-Wall' '-o' 'libtest2.so' '-shared'
'-fPIC' '-fvisibility=hidden' '-mtune=generic'
/usr/local/libexec/gcc/i686-pc-linux-gnu/4.3.2/cc1 -E -quiet -v test2.c
-mtune=generic -Wall -fPIC -fvisibility=hidden -fpch-preprocess -o test2.i
ignoring nonexistent directory
"/usr/local/lib/gcc/i686-pc-linux-gnu/4.3.2/../../../../i686-pc-linux-gnu/include"
#include "..." search starts here:
#include <...> search starts here:
/usr/local/include
/usr/local/lib/gcc/i686-pc-linux-gnu/4.3.2/include
/usr/local/lib/gcc/i686-pc-linux-gnu/4.3.2/include-fixed
/usr/include
End of search list.
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-Wall' '-o' 'libtest2.so' '-shared'
'-fPIC' '-fvisibility=hidden' '-mtune=generic'
/usr/local/libexec/gcc/i686-pc-linux-gnu/4.3.2/cc1 -fpreprocessed test2.i
-quiet -dumpbase test2.c -mtune=generic -auxbase test2 -Wall -version -fPIC
-fvisibility=hidden -o test2.s
GNU C (GCC) version 4.3.2 (i686-pc-linux-gnu)
compiled by GNU C version 4.3.2, GMP version 4.2.2, MPFR version 2.3.1.
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: 53913b99eaa90e1de01474d5b5d32b19
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-Wall' '-o' 'libtest2.so' '-shared'
'-fPIC' '-fvisibility=hidden' '-mtune=generic'
as -V -Qy -o test2.o test2.s
GNU assembler version 2.18.0 (i486-linux-gnu) using BFD version (GNU Binutils
for Ubuntu) 2.18.0.20080103
COMPILER_PATH=/usr/local/libexec/gcc/i686-pc-linux-gnu/4.3.2/:/usr/local/libexec/gcc/i686-pc-linux-gnu/4.3.2/:/usr/local/libexec/gcc/i686-pc-linux-gnu/:/usr/local/lib/gcc/i686-pc-linux-gnu/4.3.2/:/usr/local/lib/gcc/i686-pc-linux-gnu/
LIBRARY_PATH=/usr/local/lib/gcc/i686-pc-linux-gnu/4.3.2/:/usr/local/lib/gcc/i686-pc-linux-gnu/4.3.2/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-v' '-save-temps' '-Wall' '-o' 'libtest2.so' '-shared'
'-fPIC' '-fvisibility=hidden' '-mtune=generic'
/usr/local/libexec/gcc/i686-pc-linux-gnu/4.3.2/collect2 --eh-frame-hdr -m
elf_i386 -shared -o libtest2.so /usr/lib/crti.o
/usr/local/lib/gcc/i686-pc-linux-gnu/4.3.2/crtbeginS.o
-L/usr/local/lib/gcc/i686-pc-linux-gnu/4.3.2
-L/usr/local/lib/gcc/i686-pc-linux-gnu/4.3.2/../../.. test2.o -lgcc --as-needed
-lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s --no-as-needed
/usr/local/lib/gcc/i686-pc-linux-gnu/4.3.2/crtendS.o /usr/lib/crtn.o
/usr/bin/ld: test2.o: relocation R_386_GOTOFF against protected function `f2'
can not be used when making a shared object
/usr/bin/ld: final link failed: Bad value
collect2: ld returned 1 exit status
--
Summary: invalid relocation R_386_GOTOFF when using protected
function pointers
Product: gcc
Version: 4.3.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: gernot dot hillier at siemens dot com
GCC build triplet: i686-pc-linux-gnu
GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37611
