blackfin gcc-toolchain linking error math function like atan2 :undefined reference to … within watan2.o

Question

I've a problem with the classic math function linking of my bare metal program with blackfin tool chain linker. I tried many things but I cannot see why the libm.a does't provide the definitions for the function it use. Do I need to add an extra library? if yes which one?

I've put my linker verbose lign with linked libraries and the example linking error I got.

Thanks,

William

bfin-elf-ld -v  -o test_ad1836_driver -T  coreb_test_ad1836_driver.lds  --just-symbol  ../../icc_core/icc queue.o ezkit_561.o  heap_2.o  port.o tasks.o test_ad1836_driver.o list.o croutine.o user_isr.o bfin_isr.o app_c.o context_sl_asm.o cycle_count.o CFFT_Rad4_NS_NBRev.o fir_decima.o fir_decima_spl.o math_tools.o -Ttext 0x3c00000   -L /opt/uClinux/bfin-elf/bfin-elf/lib -lbffastfp -lbfdsp -lg -lc -lm -Map=test_ad1836_driver.map 
argv[0]      = 'bfin-elf-ld'
bindir       = '/opt/uClinux/bfin-elf/bin/'
tooldir      = '/opt/uClinux/bfin-elf/bin/../bfin-elf/bin/'
linker       = '/opt/uClinux/bfin-elf/bin/../bfin-elf/bin/ld.real'
elf2flt      = '/opt/uClinux/bfin-elf/bin/../bfin-elf/bin/elf2flt'
nm           = '/opt/uClinux/bfin-elf/bin/../bfin-elf/bin/nm'
objdump      = '/opt/uClinux/bfin-elf/bin/bfin-elf-objdump'
objcopy      = '/opt/uClinux/bfin-elf/bin/bfin-elf-objcopy'
ldscriptpath = '/opt/uClinux/bfin-elf/bin/../bfin-elf/bin/../lib'
Invoking: '/opt/uClinux/bfin-elf/bin/../bfin-elf/bin/ld.real' '-v' '-o' 'test_ad1836_driver' '-T' 'coreb_test_ad1836_driver.lds' '--just-symbol' '../../icc_core/icc' 'queue.o' 'ezkit_561.o' 'heap_2.o' 'port.o' 'tasks.o' 'test_ad1836_driver.o' 'list.o' 'croutine.o' 'user_isr.o' 'bfin_isr.o' 'app_c.o' 'context_sl_asm.o' 'cycle_count.o' 'CFFT_Rad4_NS_NBRev.o' 'fir_decima.o' 'fir_decima_spl.o' 'math_tools.o' '-Ttext' '0x3c00000' '-L' '/opt/uClinux/bfin-elf/bfin-elf/lib' '-lbffastfp' '-lbfdsp' '-lg' '-lc' '-lm' '-Map=test_ad1836_driver.map'
GNU ld version 2.17
/opt/uClinux/bfin-elf/bfin-elf/lib/libm.a(w_atan2.o): In function `atan2':
/usr/src/packages/BUILD/blackfin-toolchain-2010R1/gcc-4.3/newlib/libm/math/w_atan2.c:96: undefined reference to `__eqdf2'
/usr/src/packages/BUILD/blackfin-toolchain-2010R1/gcc-4.3/newlib/libm/math/w_atan2.c:96: relocation truncated to fit: R_BFIN_PCREL24 against undefined symbol `__eqdf2'
.....
/opt/uClinux/bfin-elf/bfin-elf/lib/libm.a(e_sqrt.o): In function `_ieee754_sqrt':
/usr/src/packages/BUILD/blackfin-toolchain-2010R1/gcc-4.3/newlib/libm/math/e_sqrt.c:110: undefined reference to `__muldf3'
/usr/src/packages/BUILD/blackfin-toolchain-2010R1/gcc-4.3/newlib/libm/math/e_sqrt.c:110: undefined reference to `__adddf3'

.....
/opt/uClinux/bfin-elf/bfin-elf/lib/libm.a(s_atan.o): In function `atan':
/usr/src/packages/BUILD/blackfin-toolchain-2010R1/gcc-4.3/newlib/libm/math/s_atan.c:169: undefined reference to `__muldf3'
/usr/src/packages/BUILD/blackfin-toolchain-2010R1/gcc-4.3/newlib/libm/math/s_atan.c:170: undefined reference to `__muldf3'
/usr/src/packages/BUILD/blackfin-toolchain-2010R1/gcc-4.3/newlib/libm/math/s_atan.c:172: undefined reference to `__muldf3'

Answer 1

Add -lgcc. You need the functions to compare, add and multiply C double type values, respectively, __eqdf2, __adddf3 and __muldf3.

Usually, I'd recommend using the compiler driver (gcc) instead of linking directly with ld, even for firmware/kernel type outputs, because the former will take care of the necessary startup files and compiler runtime libraries.

Answer 2

Hi I think I know the problem, blackfin is not really compatible with the maths std lib. It is why in the VDSP version the maths functions are re implemented. To solve my problem, I did convert the VDSP maths lib to gcc and it compile fine now.

Thanks

Answer 3

Actually I found a better answer,

blackfin does in fact support std math. I just had some library flag in the wrong order.

For the linker, use the following lib flag order and it should work:

/opt/uClinux/bfin-elf/bin/../bfin-elf/bin/ld.real' '-v' '-o' .... '-L' '/opt/uClinux/bfin-elf/lib/gcc/bfin-elf/4.3.5/' '-lgcc' '-L' '/opt/uClinux/bfin-elf/bfin-elf/lib' '-lbfdsp' '-lg' '-lm' '-lbffastfp' '-lc'