When calling avr-g++, the linker driver adds a call to -lgcc before any
of the user libraries entered on the command-line.
On the AVR, this causes the wrong math function implementations taken from
libgcc.a rather than the (user-supplied) libm.a.
This is different from the C compiler driver, why?
Given (any) C++ file foo.cc, using avr-gcc:
% avr-gcc -v foo.cc
Using built-in specs.
Target: avr
Configured with: ./configure --prefix=/tools/i686 --target=avr --disable-libssp
--with-dwarf2
Thread model: single
gcc version 4.1.0
/tools/i686/libexec/gcc/avr/4.1.0/cc1plus -quiet -v foo.cc -quiet -dumpbase
foo.cc -auxbase foo -version -fno-rtti -fno-enforce-eh-specs -fno-exceptions -o
/tmp/cc7jbBxg.s
ignoring nonexistent directory
"/tools/i686/lib/gcc/avr/4.1.0/../../../../include/c++/4.1.0"
ignoring nonexistent directory
"/tools/i686/lib/gcc/avr/4.1.0/../../../../include/c++/4.1.0/avr"
ignoring nonexistent directory
"/tools/i686/lib/gcc/avr/4.1.0/../../../../include/c++/4.1.0/backward"
ignoring nonexistent directory
"/tools/i686/lib/gcc/avr/4.1.0/../../../../avr/sys-include"
#include "..." search starts here:
#include <...> search starts here:
/tools/i686/lib/gcc/avr/4.1.0/include
/tools/i686/lib/gcc/avr/4.1.0/../../../../avr/include
End of search list.
GNU C++ version 4.1.0 (avr)
compiled by GNU C version 3.2.3 20030502 (Red Hat Linux 3.2.3-49).
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: e56ae0f62a848350ccb9716b24fc3bd9
/tools/i686/lib/gcc/avr/4.1.0/../../../../avr/bin/as -o /tmp/ccyX7jFq.o
/tmp/cc7jbBxg.s
/tools/i686/lib/gcc/avr/4.1.0/../../../../avr/bin/ld -m avr2
/tools/i686/lib/gcc/avr/4.1.0/../../../../avr/lib/crts8515.o
-L/tools/i686/lib/gcc/avr/4.1.0
-L/tools/i686/lib/gcc/avr/4.1.0/../../../../avr/lib /tmp/ccyX7jFq.o -lgcc -lc
-lgcc
Using avr-g++ instead of avr-gcc:
% avr-g++ -v foo.cc
Using built-in specs.
Target: avr
Configured with: ./configure --prefix=/tools/i686 --target=avr --disable-libssp
--with-dwarf2
Thread model: single
gcc version 4.1.0
/tools/i686/libexec/gcc/avr/4.1.0/cc1plus -quiet -v foo.cc -quiet -dumpbase
foo.cc -auxbase foo -version -fno-rtti -fno-enforce-eh-specs -fno-exceptions -o
/tmp/ccbXCZLa.s
ignoring nonexistent directory
"/tools/i686/lib/gcc/avr/4.1.0/../../../../include/c++/4.1.0"
ignoring nonexistent directory
"/tools/i686/lib/gcc/avr/4.1.0/../../../../include/c++/4.1.0/avr"
ignoring nonexistent directory
"/tools/i686/lib/gcc/avr/4.1.0/../../../../include/c++/4.1.0/backward"
ignoring nonexistent directory
"/tools/i686/lib/gcc/avr/4.1.0/../../../../avr/sys-include"
#include "..." search starts here:
#include <...> search starts here:
/tools/i686/lib/gcc/avr/4.1.0/include
/tools/i686/lib/gcc/avr/4.1.0/../../../../avr/include
End of search list.
GNU C++ version 4.1.0 (avr)
compiled by GNU C version 3.2.3 20030502 (Red Hat Linux 3.2.3-49).
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: e56ae0f62a848350ccb9716b24fc3bd9
/tools/i686/lib/gcc/avr/4.1.0/../../../../avr/bin/as -o /tmp/ccSHVtCa.o
/tmp/ccbXCZLa.s
/tools/i686/lib/gcc/avr/4.1.0/../../../../avr/bin/ld -m avr2
/tools/i686/lib/gcc/avr/4.1.0/../../../../avr/lib/crts8515.o
-L/tools/i686/lib/gcc/avr/4.1.0
-L/tools/i686/lib/gcc/avr/4.1.0/../../../../avr/lib /tmp/ccSHVtCa.o -lgcc -lm
-lgcc -lc -lgcc
--
Summary: Call to -lgcc added prior to user libraries
Product: gcc
Version: 4.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: j at uriah dot heep dot sax dot de
GCC host triplet: *-*-*
GCC target triplet: avr-*-*
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28718
