On Thu, Aug 15, 2019 at 4:33 PM Jan Hubicka <hubi...@ucw.cz> wrote: > > > On Fri, Aug 9, 2019 at 3:57 PM Martin Liška <mli...@suse.cz> wrote: > > > > > > Hi. > > > > > > The patch is about prevention of LTO section name clashing. > > > Now we have a situation where body of 2 functions is streamed > > > into the same ELF section. Then we'll end up with smashed data. > > > > > > Patch can bootstrap on x86_64-linux-gnu and survives regression tests. > > > > > > Ready to be installed? > > > > I think the comment should mention why we skip a leading '*' > > at all. IIRC this is some target mangling applied to DECL_ASSEMBLER_NAME? > DECL_ASSEMBLER_NAME works in a way that if it starts with "*" > it is copied verbatim to the linker ouptut. If it is w/o "*" > then user_label_prefix is applied first, see > symbol_table::assembler_names_equal_p > > So if we skip "*" one can definitly construct testcases of different > function names ending up in same section especially when > user_label_prefix is non-empty, like on Windows I think it is "_". > > > And section names cannot contain '*'? Or do we need to actually > > indentify '*fn' and 'fn' as the same? For the testcase what is the clashing > > symbol? Can't we have many so that using "0" always is broken as well? > > We may have duplicate symbols during the compile time->WPA streaming > since we do not do lto-symtab at compile time and user can use asm names > that way. This is not limited to extern inlines, so it would be nice to > make this work reliably. I also plan support for keeping multiple > function bodies defined for one symbol in cases it is necessary (glibc > checking, when optimization flags are mismatches) for WPA->ltrans > streaming. > > I was always considering option to simply use node->order ids to stream > sections. Because of way node->order is merged we area always able to > recover the ID.
Heh, that sounds like a nice idea indeed. > > It is however kind of nice to see actual names in the objdump > of the LTO .o files. I would not mind that much to see this go and it > would also save bit of space since symbol names can be long. > > Honza > > > > Richard. > > > > > Thanks, > > > Martin > > > > > > gcc/ChangeLog: > > > > > > 2019-08-09 Martin Liska <mli...@suse.cz> > > > > > > PR lto/91393 > > > PR lto/88220 > > > * lto-streamer.c (lto_get_section_name): Replace '*' leading > > > character with '0'. > > > > > > gcc/testsuite/ChangeLog: > > > > > > 2019-08-09 Martin Liska <mli...@suse.cz> > > > > > > PR lto/91393 > > > PR lto/88220 > > > * gcc.dg/lto/pr91393_0.c: New test. > > > --- > > > gcc/lto-streamer.c | 15 ++++++++++++--- > > > gcc/testsuite/gcc.dg/lto/pr91393_0.c | 11 +++++++++++ > > > 2 files changed, 23 insertions(+), 3 deletions(-) > > > create mode 100644 gcc/testsuite/gcc.dg/lto/pr91393_0.c > > > > > >
