Re: [PATCH] PR lto/61048 Define missed builtins on demand

[Ilya Palachev <i dot palachev at samsung dot com>]

On 15.10.2014 10:59, Jakub Jelinek wrote:
> On Tue, Oct 14, 2014 at 08:39:40PM +0400, Ilya Palachev wrote:
> > Attached patch fixes PR lto/61048 -
> > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61048
>
> Given that the patch just replaces an ICE with a necessary link failure, I'd say
> it is done at the wrong place, instead during the LTO option handling you
> should error out if there are incompatibilities in -fsanitize options
> (any object compiled with flag_sanitize & SANITIZE_USER_ADDRESS, but
> link done without that, ditto for SANITIZE_KERNEL_ADDRESS, SANITIZE_THREAD.
> And finally if flag_sanitize & (SANITIZE_UNDEFINED | SANITIZE_NONDEFALT)
> is non-zero but during linking it is zero (it doesn't really matter which
> exact undefined sanitization options are used at what time).

As I understand you suggest that the compiler should:
- Write compiler options with which the object file was compiled to the 
ELF format in a special section.
- Read these sections during the linking command
- Compare collected sets of options with options that were set at 
linking command.
?

Does compiler have any opportunity to save the set of options with which 
the object file was compiled inside some special ELF section? For LTO 
they the special section ".gnu.lto_.opts" is used. But not all compiler 
options are written to it:

$ gcc -fsanitize=address -c test.cpp -o test.o -flto
$ objdump --full-contents --section=.gnu.lto_.opts test.o

test.o:     file format elf64-x86-64

Contents of section .gnu.lto_.opts:
 0000 272d6665 78636570 74696f6e 73272027  '-fexceptions' '
 0010 2d666d61 74682d65 72726e6f 2720272d  -fmath-errno' '-
 0020 66736967 6e65642d 7a65726f 73272027  fsigned-zeros' '
 0030 2d667472 61707069 6e672d6d 61746827  -ftrapping-math'
 0040 20272d66 6e6f2d74 72617076 2720272d   '-fno-trapv' '-
 0050 666e6f2d 73747269 63742d6f 76657266  fno-strict-overf
 0060 6c6f7727 20272d6d 74756e65 3d67656e  low' '-mtune=gen
 0070 65726963 2720272d 6d617263 683d7838  eric' '-march=x8
 0080 362d3634 2720272d 666c746f 2700      6-64' '-flto'.

As you can see there is no "-fsanitize" option here. Only options that 
are handled in function lto_write_options in lto-opts.c are written there.

Does gcc has an opportunity to write something like ELF section 
".gnu.opts" to save all compiler options with which the object file was 
compiled?
Or we need to introduce such section? Or anything else?

> BTW, in your patches please watch formatting, you didn't use space before (.

Sorry for that. I'll check it in further patches.

> 	Jakub