Hi,

the patch

2017-07-06  Jan Hubicka  <hubicka@ucw.cz>

	* lto-wrapper.c (merge_and_complain): Do not merge
	fexceptions, fnon_call_exceptions, ftrapv, ffp_contract_, fmath_errno,
	fsigned_zeros, ftrapping_math, fwrapv.
	(append_compiler_options): Do not track these options.
	(append_linker_options): Likewie

has broken exception handling in LTO mode for targets which don't force either 
-funwind-tables or -fasynchronous-unwind-tables (i.e not x86) and do not 
default to -fdwarf2-cfi-asm (i.e. not Linux), for example SPARC/Solaris.

The problem is that the eh_frame section is no longer generated because it is 
emitted from compile_file:

    #if defined DWARF2_DEBUGGING_INFO || defined DWARF2_UNWIND_INFO
      if (dwarf2out_do_frame ())
	dwarf2out_frame_finish ();
    #endif

and this requires that either flag_unwind_tables or flag_exceptions be set.

But both -funwind-tables and -fexceptions are optimization options defaulting 
to 0 and they are reset to 0 through optimization_default_node after the last 
function is processed by the cgraph machinery.

Note that flag_exceptions is generally set to 1 in lto_init_eh very early, but 
the above mechanism overrides it.  However, flag_exceptions may *never* be set 
to 1 for a specific partition if it contains only EH-neutral functions; that's 
why I think that there is no other way than restoring the build-wide handling 
of -fexceptions before Jan's patch (hopefully it's the only affected switch).

Tested (lightly for now) on x86-64/Linux and SPARC/Solaris, OK for mainline?


2017-11-09  Eric Botcazou  <ebotcazou@adacore.com>

	* lto-opts.c (lto_write_options): Do not save -fnon-call-exceptions,
	-ffp-contract, -fmath-errno, -fsigned-zeros, -ftrapping-math, -ftrapv
	and -fwrapv.
	* lto-wrapper.c (merge_and_complain): Merge again -fexceptions.
	(append_compiler_options): Pass again -fexceptions.

-- 
Eric Botcazou