Re: [avr-gcc-list] Trouble with: relocation truncated to fit: R_AVR_13_PCREL

[Weddington, Eric]

> -----Original Message-----
> From: Georg-Johann Lay [mailto:address@hidden
> Sent: Wednesday, June 15, 2011 6:32 PM
> To: address@hidden
> Cc: Denis Chertykov; Weddington, Eric
> Subject: Trouble with: relocation truncated to fit: R_AVR_13_PCREL
> 
> Hi, running avr-gcc-4.7.0 testsuite I observe mentioned problem with
> the following command line:
> 
> avr-gcc ./gcc/testsuite/gcc.c-torture/execute/980709-1.c -include
> stdlib.h -O2 -flto -flto-partition=none -mmcu=atmega128
> -Wl,-u,vfprintf -lprintf_flt
> -Wl,-Tbss=0x802000,--defsym=__heap_end=0x80ffff -lm
> 
> For the source see
> http://gcc.gnu.org/viewcvs/trunk/gcc/testsuite/gcc.c-
> torture/execute/980709-1.c?content-type=text%2Fplain&view=co
> 
> #include <math.h>
> 
> main()
> {
>   volatile double a;
>   double c;
>   a = 32.0;
>   c = pow(a, 1.0/3.0);
>   if (c + 0.1 > 3.174802
>       && c - 0.1 < 3.174802)
>     exit (0);
>   else
>     abort ();
> }
> 
> Error message:
> 
> /local/gnu/install/gcc-
> 4.7/lib/gcc/avr/4.7.0/../../../../avr/lib/avr51/libc.a(log.o):../../../../
> ../source/avr-libc-1.7.1/libm/fplib/log.S:96:
> relocation truncated to fit: R_AVR_13_PCREL against symbol `__addsf3'
> defined in .text section in
> /local/gnu/install/gcc-4.7/lib/gcc/avr/4.7.0/avr51/libgcc.a(_addsub_sf.o)
> /local/gnu/install/gcc-
> 4.7/lib/gcc/avr/4.7.0/../../../../avr/lib/avr51/libc.a(log.o):../../../../
> ../source/avr-libc-1.7.1/libm/fplib/log.S:100:
> relocation truncated to fit: R_AVR_13_PCREL against symbol `__addsf3'
> defined in .text section in
> /local/gnu/install/gcc-4.7/lib/gcc/avr/4.7.0/avr51/libgcc.a(_addsub_sf.o)
> /local/gnu/install/gcc-
> 4.7/lib/gcc/avr/4.7.0/../../../../avr/lib/avr51/libc.a(modf.o):../../../..
> /../source/avr-libc-1.7.1/libm/fplib/modf.S:90:
> relocation truncated to fit: R_AVR_13_PCREL against symbol `__subsf3'
> defined in .text section in
> /local/gnu/install/gcc-4.7/lib/gcc/avr/4.7.0/avr51/libgcc.a(_addsub_sf.o)
> 
> The command line is a typical commandline used in testsuite regression
> test runs for avr-gcc.
> 
> $avr-libc/libm/fplib/log.S shows explicit use of RCALL/RJMP to
> external symbols which should definitely not be there.
> 
> Is this worth a bug report or is someone already working on this?
> 
> I've seen similar topics in avr forums then and when...
> 
> Then, I wonder why _addsub_sf.o is dragged in (by __addsf3 or
> __subsf3) even though avr-libc implements that.
> 
> I've already consulted Jörg about that, and that the hackish
> "overwrite" of stuff from libgcc by avr-libc does not always work as
> intended.

Do we know why that is the case, why it's not working for certain cases? 
Because it does work in other cases.

Eric



> It's obvious that the desired solution was to have that code
> integrated into libgcc instead of in avr-libc (which is not the case
> for reasons we all know).
> 
> So I proposed a fix that involves less administrative and
> implementational overhead and resource:
> 
> * Add a new option to avr-gcc: -mavr-libc (on by default)
> 
> * If -mavr-libc is on, use gcc optabs to emit other function names
>   for distinct function in libgcc, e.g. __avrlibc___addsf3 instead
>   of __addsf3.
> 
> * Sprinkle some new __avrlibc_* labels over avr-libc like, e.g:
>      .global __avrlibc___addsf3
>      .global __addsf3
>      __avrlibc___addsf3:
>      __addsf3:
>   instead of
>      .global __addsf3
>      __addsf3:
> 
> That way the bulky libgcc implementations could be bypassed. It would
> be a minimal change in avr backend and it is the preferred way to
> interface with a 3rd party library (like gofast).
> 
> Johann