Re: [libunwind] _ReadSLEB and _ReadULEB

[Tommy Hoffner]

David Mosberger skrev:
> > > > > > On Wed, 09 Feb 2005 12:31:16 +0100, Tommy Hoffner
>
> <address@hidden> said:
>
>   Tommy> Whats the story behind _ReadSLEB and _ReadULEB?  I spent
>   Tommy> quite a lot of time locating a bug where the personality
>   Tommy> routine got in to an endless loop. Finally I fixed it by
>   Tommy> removing the two mentioned routines from the libunwind
>   Tommy> library (so it used the libipr versions instead)..
>
> The routines were added solely for compatibility with ICC. ;-(
> Unfortunately, libunwind.so.6 as shipped with ICC exports those
> routines so in order to use my libunwind as a replacement, we have to
> export those routines, too.
Hm, current libunwind (Intel's/Dinkumware's) and libipr both contain the same 
object file (read_leb.o).

  I don't see off-hand what's wrong.  AFAICS,
> the implementations should be compatible.
Enclosing an example that fails for me. The first catch works and the second 
loops, so swapping them makes the other one fail.

/Tommy

PS
I built the library with icpc ver 8.1, which I thought made sense since the 
functions are to be used in that context :-)
DS.

--------------Makefile-------------------------
CXX=icpc -gcc-name=gcc-3.4
CC=icpc -gcc-name=gcc-3.4
LDFLAGS=-L/home/uabhoto/src/test/libunwind-0.98.3/src/.libs/ -lunwind
#CXX=g++-3.4
#CC=g++-3.4

CXXFLAGS=-O0 -g

LEBbug: LEBbug.o

clean:
        rm LEBbug LEBbug.o
---------------LEBbug.C--------------------------------
#define UNW_LOCAL_ONLY
#include <libunwind.h>
#include <stdio.h>

int
main (int argc, char *argv[])
{
  unw_dyn_info_t di;
  int execptype=0;

  try {
    if(argc>1)
      throw("Exception");
    else
      throw(7);
  }
  catch (const char *p) {
    printf("SUCCESS! (Caught %s)\n\n",p);
  }
  catch (const int i) {
    printf("SUCCESS! (Caught %d)\n\n",i);
  }

  _U_dyn_cancel (&di); //Just to ensure that I link towards the right library
  return -1;
}
-------------------------------------------------------
> Do you know why there was an endless loop?
It loops in the personality routine calling 
_Z21match_exception_typesPSt9type_infoS0_PvPS1_ once and _ReadSLEB twice for 
each turn so it seems to me that it fails to match the exception type and fails 
to progress to the next excepton type (or realizing that it is at the end of 
possible types), but whether it does wrong there or if this loop is a result of 
a problem in the previous step i don't know.

>         --david

/Tommy

--
Tommy Hoffner
Senior Software Designer
Compiler Technology

Ericsson AB
Development Unit Core Network Evolution
Tel:    +46 13 23 57 12
Fax:    +46 13 28 73 71
SMS/MMS:+46 730 43 61 56
address@hidden
www.ericsson.com

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