------- Comment #13 from ebotcazou at gcc dot gnu dot org 2008-11-19 18:51
-------
> I'm a bit unsure how to test this right now: what I find is that C objects
> have read-only .eh_frame sections and use .cfi* directives, while C++, Java
> and Ada objects have read-write .eh_frame sections and still use .eh_frame
> sections directly emitted by the compiler.
The decision is made in dwarf2out_do_cfi_asm:
/* Decide whether to emit frame unwind via assembler directives. */
int
dwarf2out_do_cfi_asm (void)
{
int enc;
#ifdef MIPS_DEBUGGING_INFO
return false;
#endif
if (!flag_dwarf2_cfi_asm || !dwarf2out_do_frame ())
return false;
if (!eh_personality_libfunc)
return true;
if (!HAVE_GAS_CFI_PERSONALITY_DIRECTIVE)
return false;
/* Make sure the personality encoding is one the assembler can support.
In particular, aligned addresses can't be handled. */
enc = ASM_PREFERRED_EH_DATA_FORMAT (/*code=*/2,/*global=*/1);
if ((enc & 0x70) != 0 && (enc & 0x70) != DW_EH_PE_pcrel)
return false;
enc = ASM_PREFERRED_EH_DATA_FORMAT (/*code=*/0,/*global=*/0);
if ((enc & 0x70) != 0 && (enc & 0x70) != DW_EH_PE_pcrel)
return false;
return true;
}
On Solaris with Sun ld, ASM_PREFERRED_EH_DATA_FORMAT is defined so that at
least one of the 2 tests will always return false. Therefore the only way
to have dwarf2out_do_cfi_asm return true is
if (!eh_personality_libfunc)
return true;
The C++, Java and Ada compilers unconditionally register their personality
routine, whereas the C compiler doesn't, even with -fexceptions: if there
is no EH action in the code, it doesn't register it. Hence the discrepancy.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37463
