> Hi, > > the patch > > 2017-07-06 Jan Hubicka <hubi...@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).
I am not sure I follow your argumentation here. flag_exceptions is optimization which means that one should not test it globally. For that reason I would just change dwarf2out to simply trigger dwarf2out_frame_finish if any of the compiled functions needed it (had flag_exceptions set). My readon of lto-wrapper is that it will set flag_exceptions for whole compilation unit when one of compilation units were copmiled with flag_exceptions. How that helps the neutral functions? Honza
